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Re: patch 2/2 debuginfod server etc.


Hi,

On Mon, 2019-10-28 at 15:07 -0400, Frank Ch. Eigler wrote:
> Add the server to the debuginfod/ subdirectory.  This is a highly
> multithreaded c++11 program (still buildable on rhel7's gcc 4.8,
> which is only partly c++11 compliant).  Includes an initial suite
> of tests, man pages, and a sample systemd service.

Some comments on debuginfod.cxx.

> diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
> new file mode 100644
> index 000000000000..c9d5b271b328
> --- /dev/null
> +++ b/debuginfod/debuginfod.cxx
> @@ -0,0 +1,2501 @@
> +/* Debuginfo-over-http server.
> +   Copyright (C) 2019 Red Hat, Inc.
> +   This file is part of elfutils.
> +
> +   This file is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   elfutils is distributed in the hope that it will be useful, but
> +   WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +
> +/* cargo-cult from libdwfl linux-kernel-modules.c */
> +/* In case we have a bad fts we include this before config.h because it
> +   can't handle _FILE_OFFSET_BITS.
> +   Everything we need here is fine if its declarations just come first.
> +   Also, include sys/types.h before fts. On some systems fts.h is not self
> +   contained. */
> +#ifdef BAD_FTS
> +  #include <sys/types.h>
> +  #include <fts.h>
> +#endif

Yeah, this is unfortunate, thanks for also adopting it for the client
code.

> +#ifdef HAVE_CONFIG_H
> +  #include "config.h"
> +#endif
> +
> +extern "C" {
> +#include "printversion.h"
> +}
> +
> +#include "debuginfod.h"
> +#include <dwarf.h>
> +
> +#include <argp.h>
> +#ifdef __GNUC__
> +#undef __attribute__ /* glibc bug - rhbz 1763325 */
> +#endif

Urgh. But yeah.

> +#include <unistd.h>
> +#include <stdlib.h>
> +#include <error.h>
> +// #include <libintl.h> // not until it supports C++ << better
> +#include <locale.h>
> +#include <pthread.h>
> +#include <signal.h>
> +#include <sys/stat.h>
> +#include <sys/time.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <netdb.h>
> +
> +
> +/* If fts.h is included before config.h, its indirect inclusions may not
> +   give us the right LFS aliases of these functions, so map them manually.  */
> +#ifdef BAD_FTS
> +  #ifdef _FILE_OFFSET_BITS
> +    #define open open64
> +    #define fopen fopen64
> +  #endif
> +#else
> +  #include <sys/types.h>
> +  #include <fts.h>
> +#endif

yeah :{

> +#include <cstring>
> +#include <vector>
> +#include <set>
> +#include <string>
> +#include <iostream>
> +#include <iomanip>
> +#include <ostream>
> +#include <sstream>
> +#include <mutex>
> +#include <condition_variable>
> +#include <thread>
> +// #include <regex> // on rhel7 gcc 4.8, not competent
> +#include <regex.h>
> +// #include <algorithm>
> +using namespace std;
> +
> +#include <gelf.h>
> +#include <libdwelf.h>
> +
> +#include <microhttpd.h>
> +#include <curl/curl.h>
> +#include <archive.h>
> +#include <archive_entry.h>
> +#include <sqlite3.h>
> +
> +#ifdef __linux__
> +#include <sys/syscall.h>
> +#endif
> +
> +
> +// Roll this identifier for every sqlite schema incompatiblity.
> +#define BUILDIDS "buildids9"
> +
> +#if SQLITE_VERSION_NUMBER >= 3008000
> +#define WITHOUT_ROWID "without rowid"
> +#else
> +#define WITHOUT_ROWID ""
> +#endif
> +
> +static const char DEBUGINFOD_SQLITE_DDL[] =
> +  "pragma foreign_keys = on;\n"
> +  "pragma synchronous = 0;\n" // disable fsync()s - this cache is disposable across a machine crash
> +  "pragma journal_mode = wal;\n" // https://sqlite.org/wal.html
> +  "pragma wal_checkpoint = truncate;\n" // clean out any preexisting wal file
> +  "pragma journal_size_limit = 0;\n" // limit steady state file (between grooming, which also =truncate's)
> +  "pragma auto_vacuum = incremental;\n" // https://sqlite.org/pragma.html
> +  "pragma busy_timeout = 1000;\n" // https://sqlite.org/pragma.html ; 
> +  // NB: all these are overridable with -D option
> +
> +  // Normalization table for interning file names
> +  "create table if not exists " BUILDIDS "_files (\n"
> +  "        id integer primary key not null,\n"
> +  "        name text unique not null\n"
> +  "        );\n"
> +  // Normalization table for interning buildids
> +  "create table if not exists " BUILDIDS "_buildids (\n"
> +  "        id integer primary key not null,\n"
> +  "        hex text unique not null);\n"
> +  // Track the completion of scanning of a given file & sourcetype at given time
> +  "create table if not exists " BUILDIDS "_file_mtime_scanned (\n"
> +  "        mtime integer not null,\n"
> +  "        file integer not null,\n"
> +  "        size integer not null,\n" // in bytes
> +  "        sourcetype text(1) not null\n"
> +  "            check (sourcetype IN ('F', 'R')),\n"
> +  "        foreign key (file) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        primary key (file, mtime, sourcetype)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  "create table if not exists " BUILDIDS "_f_de (\n"
> +  "        buildid integer not null,\n"
> +  "        debuginfo_p integer not null,\n"
> +  "        executable_p integer not null,\n"
> +  "        file integer not null,\n"
> +  "        mtime integer not null,\n"
> +  "        foreign key (file) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (buildid) references " BUILDIDS "_buildids(id) on update cascade on delete cascade,\n"
> +  "        primary key (buildid, file, mtime)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  "create table if not exists " BUILDIDS "_f_s (\n"
> +  "        buildid integer not null,\n"
> +  "        artifactsrc integer not null,\n"
> +  "        file integer not null,\n" // NB: not necessarily entered into _mtime_scanned
> +  "        mtime integer not null,\n"
> +  "        foreign key (file) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (artifactsrc) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (buildid) references " BUILDIDS "_buildids(id) on update cascade on delete cascade,\n"
> +  "        primary key (buildid, artifactsrc, file, mtime)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  "create table if not exists " BUILDIDS "_r_de (\n"
> +  "        buildid integer not null,\n"
> +  "        debuginfo_p integer not null,\n"
> +  "        executable_p integer not null,\n"
> +  "        file integer not null,\n"
> +  "        mtime integer not null,\n"
> +  "        content integer not null,\n"
> +  "        foreign key (file) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (content) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (buildid) references " BUILDIDS "_buildids(id) on update cascade on delete cascade,\n"
> +  "        primary key (buildid, debuginfo_p, executable_p, file, content, mtime)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  "create table if not exists " BUILDIDS "_r_sref (\n" // outgoing dwarf sourcefile references from rpm
> +  "        buildid integer not null,\n"
> +  "        artifactsrc integer not null,\n"
> +  "        foreign key (artifactsrc) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (buildid) references " BUILDIDS "_buildids(id) on update cascade on delete cascade,\n"
> +  "        primary key (buildid, artifactsrc)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  "create table if not exists " BUILDIDS "_r_sdef (\n" // rpm contents that may satisfy sref
> +  "        file integer not null,\n"
> +  "        mtime integer not null,\n"
> +  "        content integer not null,\n"
> +  "        foreign key (file) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        foreign key (content) references " BUILDIDS "_files(id) on update cascade on delete cascade,\n"
> +  "        primary key (content, file, mtime)\n"
> +  "        ) " WITHOUT_ROWID ";\n"
> +  // create views to glue together some of the above tables, for webapi D queries
> +  "create view if not exists " BUILDIDS "_query_d as \n"
> +  "select\n"
> +  "        b.hex as buildid, n.mtime, 'F' as sourcetype, f0.name as source0, n.mtime as mtime, null as source1\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_f_de n\n"
> +  "        where b.id = n.buildid and f0.id = n.file and n.debuginfo_p = 1\n"
> +  "union all select\n"
> +  "        b.hex as buildid, n.mtime, 'R' as sourcetype, f0.name as source0, n.mtime as mtime, f1.name as source1\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_files f1, " BUILDIDS "_r_de n\n"
> +  "        where b.id = n.buildid and f0.id = n.file and f1.id = n.content and n.debuginfo_p = 1\n"
> +  ";"
> +  // ... and for E queries
> +  "create view if not exists " BUILDIDS "_query_e as \n"
> +  "select\n"
> +  "        b.hex as buildid, n.mtime, 'F' as sourcetype, f0.name as source0, n.mtime as mtime, null as source1\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_f_de n\n"
> +  "        where b.id = n.buildid and f0.id = n.file and n.executable_p = 1\n"
> +  "union all select\n"
> +  "        b.hex as buildid, n.mtime, 'R' as sourcetype, f0.name as source0, n.mtime as mtime, f1.name as source1\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_files f1, " BUILDIDS "_r_de n\n"
> +  "        where b.id = n.buildid and f0.id = n.file and f1.id = n.content and n.executable_p = 1\n"
> +  ";"
> +  // ... and for S queries
> +  "create view if not exists " BUILDIDS "_query_s as \n"
> +  "select\n"
> +  "        b.hex as buildid, fs.name as artifactsrc, 'F' as sourcetype, f0.name as source0, n.mtime as mtime, null as source1, null as source0ref\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_files fs, " BUILDIDS "_f_s n\n"
> +  "        where b.id = n.buildid and f0.id = n.file and fs.id = n.artifactsrc\n"
> +  "union all select\n"
> +  "        b.hex as buildid, f1.name as artifactsrc, 'R' as sourcetype, f0.name as source0, sd.mtime as mtime, f1.name as source1, fsref.name as source0ref\n"
> +  "        from " BUILDIDS "_buildids b, " BUILDIDS "_files f0, " BUILDIDS "_files f1, " BUILDIDS "_files fsref, "
> +  "        " BUILDIDS "_r_sdef sd, " BUILDIDS "_r_sref sr, " BUILDIDS "_r_de sde\n"
> +  "        where b.id = sr.buildid and f0.id = sd.file and fsref.id = sde.file and f1.id = sd.content\n"
> +  "        and sr.artifactsrc = sd.content and sde.buildid = sr.buildid\n"
> +  ";"
> +  // and for startup overview counts
> +  "drop view if exists " BUILDIDS "_stats;\n"
> +  "create view if not exists " BUILDIDS "_stats as\n"
> +  "          select 'file d/e' as label,count(*) as quantity from " BUILDIDS "_f_de\n"
> +  "union all select 'file s',count(*) from " BUILDIDS "_f_s\n"
> +  "union all select 'rpm d/e',count(*) from " BUILDIDS "_r_de\n"
> +  "union all select 'rpm sref',count(*) from " BUILDIDS "_r_sref\n"
> +  "union all select 'rpm sdef',count(*) from " BUILDIDS "_r_sdef\n"  
> +  "union all select 'buildids',count(*) from " BUILDIDS "_buildids\n"
> +  "union all select 'filenames',count(*) from " BUILDIDS "_files\n"
> +  "union all select 'files scanned (#)',count(*) from " BUILDIDS "_file_mtime_scanned\n"
> +  "union all select 'files scanned (mb)',coalesce(sum(size)/1024/1024,0) from " BUILDIDS "_file_mtime_scanned\n"
> +#if SQLITE_VERSION_NUMBER >= 3016000
> +  "union all select 'index db size (mb)',page_count*page_size/1024/1024 as size FROM pragma_page_count(), pragma_page_size()\n"
> +#endif
> +  ";\n"
> +  
> +// schema change history & garbage collection
> +//  
> +// XXX: we could have migration queries here to bring prior-schema
> +// data over instead of just dropping it.
> +//
> +// buildids9: widen the mtime_scanned table
> +  "" // <<< we are here
> +// buildids8: slim the sref table
> +  "drop table if exists buildids8_f_de;\n"
> +  "drop table if exists buildids8_f_s;\n"
> +  "drop table if exists buildids8_r_de;\n"
> +  "drop table if exists buildids8_r_sref;\n"
> +  "drop table if exists buildids8_r_sdef;\n"
> +  "drop table if exists buildids8_file_mtime_scanned;\n"
> +  "drop table if exists buildids8_files;\n"
> +  "drop table if exists buildids8_buildids;\n"
> +// buildids7: separate _norm table into dense subtype tables
> +  "drop table if exists buildids7_f_de;\n"
> +  "drop table if exists buildids7_f_s;\n"
> +  "drop table if exists buildids7_r_de;\n"
> +  "drop table if exists buildids7_r_sref;\n"
> +  "drop table if exists buildids7_r_sdef;\n"
> +  "drop table if exists buildids7_file_mtime_scanned;\n"
> +  "drop table if exists buildids7_files;\n"
> +  "drop table if exists buildids7_buildids;\n"
> +// buildids6: drop bolo/rfolo again, represent sources / rpmcontents in main table
> +  "drop table if exists buildids6_norm;\n"
> +  "drop table if exists buildids6_files;\n"
> +  "drop table if exists buildids6_buildids;\n"
> +  "drop view if exists buildids6;\n"
> +// buildids5: redefine srcfile1 column to be '.'-less (for rpms)
> +  "drop table if exists buildids5_norm;\n"
> +  "drop table if exists buildids5_files;\n"
> +  "drop table if exists buildids5_buildids;\n"
> +  "drop table if exists buildids5_bolo;\n"
> +  "drop table if exists buildids5_rfolo;\n"  
> +  "drop view if exists buildids5;\n"
> +// buildids4: introduce rpmfile RFOLO
> +  "drop table if exists buildids4_norm;\n"
> +  "drop table if exists buildids4_files;\n"
> +  "drop table if exists buildids4_buildids;\n"
> +  "drop table if exists buildids4_bolo;\n"
> +  "drop table if exists buildids4_rfolo;\n"  
> +  "drop view if exists buildids4;\n"
> +// buildids3*: split out srcfile BOLO
> +  "drop table if exists buildids3_norm;\n"
> +  "drop table if exists buildids3_files;\n"
> +  "drop table if exists buildids3_buildids;\n"
> +  "drop table if exists buildids3_bolo;\n"
> +  "drop view if exists buildids3;\n"
> +// buildids2: normalized buildid and filenames into interning tables;
> +  "drop table if exists buildids2_norm;\n"
> +  "drop table if exists buildids2_files;\n"
> +  "drop table if exists buildids2_buildids;\n"  
> +  "drop view if exists buildids2;\n"
> +  // buildids1: made buildid and artifacttype NULLable, to represent cached-negative
> +//           lookups from sources, e.g. files or rpms that contain no buildid-indexable content
> +  "drop table if exists buildids1;\n"
> +// buildids: original
> +  "drop table if exists buildids;\n"
> +  ;
> +
> +static const char DEBUGINFOD_SQLITE_CLEANUP_DDL[] =
> +  "pragma wal_checkpoint = truncate;\n" // clean out any preexisting wal file
> +  ;

Is there any way these sql DDL statements can be put somewhere else?
It is IMHO a little ugly to have them in the C++ source code as string
constants. Could they be installed as text/.sql files and loaded by the
code from some config dir? I realize it is nice that debuginfod is
almost completely self-contained in this one file. But if it isn't too
much work to split this out I think it would be really nice.

> +/* Name and version of program.  */
> +/* ARGP_PROGRAM_VERSION_HOOK_DEF = print_version; */ // not this simple for C++

Probably because of the __asm and function type trickery.
I see it works by direct assignment in main ().

> +/* Bug report address.  */
> +ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
> +
> +/* Definitions of arguments for argp functions.  */
> +static const struct argp_option options[] =
> +  {
> +   // NB: The -F and -R options were documented in public
> +   // presentations before they were made unnecessary (by always
> +   // implying both -F and -R for any given PATH).  We keep the
> +   // options as hidden no-ops for compatibility.
> +   //
> +   // { NULL, 0, NULL, OPTION_HIDDEN, "Sources:", 1 },
> +   { "scan-file-dir", 'F', NULL, OPTION_HIDDEN, "Scan ELF/DWARF files under following directories.", 0 },
> +   { "scan-rpm-dir", 'R', NULL, OPTION_HIDDEN, "Scan RPM files under following directories.", 0 },
> +   // "source-oci-imageregistry"  ... 
> +  
> +   { NULL, 0, NULL, 0, "Options:", 2 },
> +   { "rescan-time", 't', "SECONDS", 0, "Number of seconds to wait between rescans, 0=disable.", 0 },
> +   { "groom-time", 'g', "SECONDS", 0, "Number of seconds to wait between database grooming, 0=disable.", 0 },
> +   { "maxigroom", 'G', NULL, 0, "Run a complete database groom/shrink pass at startup.", 0 },
> +   { "concurrency", 'c', "NUM", 0, "Limit scanning thread concurrency to NUM.", 0 },
> +   { "include", 'I', "REGEX", 0, "Include files matching REGEX, default=all.", 0 },
> +   { "exclude", 'X', "REGEX", 0, "Exclude files matching REGEX, default=none.", 0 },
> +   { "port", 'p', "NUM", 0, "HTTP port to listen on, default 8002.", 0 },
> +   { "database", 'd', "FILE", 0, "Path to sqlite database.", 0 },
> +   { "ddl", 'D', "SQL", 0, "Apply extra sqlite ddl/pragma to connection.", 0 },
> +   { "verbose", 'v', NULL, 0, "Increase verbosity.", 0 },
> +    
> +   { NULL, 0, NULL, 0, NULL, 0 }
> +  };
> +
> +/* Short description of program.  */
> +static const char doc[] = "Serve debuginfo-related content across HTTP from files under PATHs.";
> +
> +/* Strings for arguments in help texts.  */
> +static const char args_doc[] = "[PATH ...]";
> +
> +/* Prototype for option handler.  */
> +static error_t parse_opt (int key, char *arg, struct argp_state *state);
> +
> +/* Data structure to communicate with argp functions.  */
> +static struct argp argp =
> +  {
> +   options, parse_opt, args_doc, doc, NULL, NULL, NULL
> +  };

OK.

> +static string db_path;
> +static sqlite3 *db;
> +static unsigned verbose;
> +static volatile sig_atomic_t interrupted = 0;
> +static volatile sig_atomic_t sigusr1 = 0;
> +static volatile sig_atomic_t sigusr2 = 0;
> +static unsigned http_port = 8002;
> +static unsigned rescan_s = 300;
> +static unsigned groom_s = 86400;
> +static unsigned maxigroom = false;
> +static unsigned concurrency = std::thread::hardware_concurrency() ?: 1;
> +static set<string> source_paths;
> +static vector<string> extra_ddl;
> +static regex_t file_include_regex;
> +static regex_t file_exclude_regex;
> +
> +/* Handle program arguments.  */
> +static error_t
> +parse_opt (int key, char *arg,
> +	   struct argp_state *state __attribute__ ((unused)))
> +{
> +  int rc;
> +  switch (key)
> +    {
> +    case 'v': verbose ++; break;
> +    case 'd': db_path = string(arg); break;
> +    case 'p': http_port = (unsigned) atoi(arg);
> +      if (http_port > 65535) argp_failure(state, 1, EINVAL, "port number");
> +      break;
> +    case 'F': break; // ignored; blog post compatibility
> +    case 'R': break; // ignored; blog post compatibility
> +    case 'D': extra_ddl.push_back(string(arg)); break;
> +    case 't':
> +      rescan_s = (unsigned) atoi(arg);
> +      break;
> +    case 'g':
> +      groom_s = (unsigned) atoi(arg);
> +      break;
> +    case 'G':
> +      maxigroom = true;
> +      break;
> +    case 'c':
> +      concurrency = (unsigned) atoi(arg);
> +      if (concurrency < 1) concurrency = 1;
> +      break;
> +    case 'I':
> +      // NB: no problem with unconditional free here - an earlier failed regcomp would exit program
> +      regfree (&file_include_regex);
> +      rc = regcomp (&file_include_regex, arg, REG_EXTENDED|REG_NOSUB);
> +      if (rc != 0)
> +        argp_failure(state, 1, EINVAL, "regular expession");        
> +      break;
> +    case 'X':
> +      regfree (&file_exclude_regex);
> +      rc = regcomp (&file_exclude_regex, arg, REG_EXTENDED|REG_NOSUB);
> +      if (rc != 0)
> +        argp_failure(state, 1, EINVAL, "regular expession");        
> +      break;
> +    case ARGP_KEY_ARG:
> +      source_paths.insert(string(arg));
> +      break;
> +      // case 'h': argp_state_help (state, stderr, ARGP_HELP_LONG|ARGP_HELP_EXIT_OK);
> +    default: return ARGP_ERR_UNKNOWN;
> +    }
> +
> +  return 0;
> +}

OK.

> +////////////////////////////////////////////////////////////////////////
> +
> +
> +// represent errors that may get reported to an ostream and/or a libmicrohttpd connection
> +
> +struct reportable_exception
> +{
> +  int code;
> +  string message;
> +
> +  reportable_exception(int c, const string& m): code(c), message(m) {}
> +  reportable_exception(const string& m): code(503), message(m) {}
> +  reportable_exception(): code(503), message() {}
> +  
> +  void report(ostream& o) const; // defined under obatched() class below
> +  
> +  int mhd_send_response(MHD_Connection* c) const {
> +    MHD_Response* r = MHD_create_response_from_buffer (message.size(),
> +                                                       (void*) message.c_str(),
> +                                                       MHD_RESPMEM_MUST_COPY);
> +    int rc = MHD_queue_response (c, code, r);
> +    MHD_destroy_response (r);
> +    return rc;
> +  }
> +};
> +
> +
> +struct sqlite_exception: public reportable_exception
> +{
> +  sqlite_exception(int rc, const string& msg):
> +    reportable_exception(string("sqlite3 error: ") + msg + ": " + string(sqlite3_errstr(rc) ?: "?")) {}
> +};
> +
> +struct libc_exception: public reportable_exception
> +{
> +  libc_exception(int rc, const string& msg):
> +    reportable_exception(string("libc error: ") + msg + ": " + string(strerror(rc) ?: "?")) {}
> +};
> +
> +
> +struct archive_exception: public reportable_exception
> +{
> +  archive_exception(const string& msg):
> +    reportable_exception(string("libarchive error: ") + msg) {}
> +  archive_exception(struct archive* a, const string& msg):
> +    reportable_exception(string("libarchive error: ") + msg + ": " + string(archive_error_string(a) ?: "?")) {}
> +};
> +
> +
> +struct elfutils_exception: public reportable_exception
> +{
> +  elfutils_exception(int rc, const string& msg):
> +    reportable_exception(string("elfutils error: ") + msg + ": " + string(elf_errmsg(rc) ?: "?")) {}
> +};

OK. Nice.

> +////////////////////////////////////////////////////////////////////////
> +
> +// a c++ counting-semaphore class ... since we're c++11 not c++20
> +
> +class semaphore
> +{
> +public:
> +  semaphore (unsigned c=1): count(c) {}
> +  inline void notify () {
> +    unique_lock<mutex> lock(mtx);
> +    count++;
> +    cv.notify_one();
> +  }
> +  inline void wait() {
> +    unique_lock<mutex> lock(mtx);
> +    while (count == 0)
> +      cv.wait(lock);
> +    count--;
> +  }
> +private:
> +  mutex mtx;
> +  condition_variable cv;
> +  unsigned count;
> +};
> +
> +
> +class semaphore_borrower
> +{
> +public:
> +  semaphore_borrower(semaphore* s): sem(s) { sem->wait(); }
> +  ~semaphore_borrower() { sem->notify(); }
> +private:
> +  semaphore* sem;
> +};

OK.

> +////////////////////////////////////////////////////////////////////////
> +
> +
> +// Print a standard timestamp.
> +static ostream&
> +timestamp (ostream &o)
> +{
> +  time_t now;
> +  time (&now);
> +  char *now2 = ctime (&now);
> +  if (now2) {
> +    now2[19] = '\0';                // overwrite \n
> +  }

I think you want to use ctime_r with a stack allocated char[26].
Also does the now2[19] always work? Isn't it better to strchr for the
'\n'. Or maybe just use strftime "%c"?

> +  return o << "[" << (now2 ? now2 : "") << "] "
> +           << "(" << getpid ()
> +#ifdef __linux__
> +           << "/" << syscall(SYS_gettid)
> +#else
> +           << "/" << pthread_self()
> +#endif
> +           << "): ";
> +}

I see this code got slightly changed in patch 5 (metrics).
Note that newer glibc actually define a function called gettid:
https://sourceware.org/bugzilla/show_bug.cgi?id=6399
So you might want to rename it to something that doesn't accidentally
clashes.

> +
> +// A little class that impersonates an ostream to the extent that it can
> +// take << streaming operations.  It batches up the bits into an internal
> +// stringstream until it is destroyed; then flushes to the original ostream.
> +// It adds a timestamp
> +class obatched
> +{
> +private:
> +  ostream& o;
> +  stringstream stro;
> +  static mutex lock;
> +public:
> +  obatched(ostream& oo, bool timestamp_p = true): o(oo)
> +  {
> +    if (timestamp_p)
> +      timestamp(stro);
> +  }
> +  ~obatched()
> +  {
> +    unique_lock<mutex> do_not_cross_the_streams(obatched::lock);
> +    o << stro.str();
> +    o.flush();
> +  }
> +  operator ostream& () { return stro; }
> +  template <typename T> ostream& operator << (const T& t) { stro << t; return stro; }
> +};
> +mutex obatched::lock; // just the one, since cout/cerr iostreams are not thread-safe
> +
> +
> +void reportable_exception::report(ostream& o) const {
> +  obatched(o) << message << endl;
> +}

OK. Although I find these class methods defined for other classes
somewhat confusing.

> +
> +////////////////////////////////////////////////////////////////////////
> +
> +
> +// RAII style sqlite prepared-statement holder that matches { } block lifetime
> +
> +struct sqlite_ps
> +{
> +private:
> +  sqlite3* db;
> +  const string nickname;
> +  const string sql;
> +  sqlite3_stmt *pp;
> +  
> +  sqlite_ps(const sqlite_ps&); // make uncopyable
> +  sqlite_ps& operator=(const sqlite_ps &); // make unassignable
> +
> +public:
> +  sqlite_ps (sqlite3* d, const string& n, const string& s): db(d), nickname(n), sql(s) {
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " prep " << sql << endl;
> +    int rc = sqlite3_prepare_v2 (db, sql.c_str(), -1 /* to \0 */, & this->pp, NULL);
> +    if (rc != SQLITE_OK)
> +      throw sqlite_exception(rc, "prepare " + sql);
> +  }
> +
> +  sqlite_ps& reset()
> +  {
> +    sqlite3_reset(this->pp);
> +    return *this;
> +  }
> +  
> +  sqlite_ps& bind(int parameter, const string& str)
> +  {
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " bind " << parameter << "=" << str << endl;
> +    int rc = sqlite3_bind_text (this->pp, parameter, str.c_str(), -1, SQLITE_TRANSIENT);
> +    if (rc != SQLITE_OK)
> +      throw sqlite_exception(rc, "sqlite3 bind");
> +    return *this;
> +  }
> +
> +  sqlite_ps& bind(int parameter, int64_t value)
> +  {
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " bind " << parameter << "=" << value << endl;
> +    int rc = sqlite3_bind_int64 (this->pp, parameter, value);
> +    if (rc != SQLITE_OK)
> +      throw sqlite_exception(rc, "sqlite3 bind");
> +    return *this;
> +  }
> +
> +  sqlite_ps& bind(int parameter)
> +  {
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " bind " << parameter << "=" << "NULL" << endl;
> +    int rc = sqlite3_bind_null (this->pp, parameter);
> +    if (rc != SQLITE_OK)
> +      throw sqlite_exception(rc, "sqlite3 bind");
> +    return *this;
> +  }
> +
> +  
> +  void step_ok_done() {
> +    int rc = sqlite3_step (this->pp);
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " step-ok-done(" << sqlite3_errstr(rc) << ") " << sql << endl;
> +    if (rc != SQLITE_OK && rc != SQLITE_DONE && rc != SQLITE_ROW)
> +      throw sqlite_exception(rc, "sqlite3 step");
> +    (void) sqlite3_reset (this->pp);
> +  }
> +
> +  
> +  int step() {
> +    int rc = sqlite3_step (this->pp);
> +    if (verbose > 4)
> +      obatched(clog) << nickname << " step(" << sqlite3_errstr(rc) << ") " << sql << endl;
> +    return rc;
> +  }
> +
> +  
> +
> +  ~sqlite_ps () { sqlite3_finalize (this->pp); }
> +  operator sqlite3_stmt* () { return this->pp; }
> +};
> +
> +
> +////////////////////////////////////////////////////////////////////////
> +
> +// RAII style templated autocloser
> +
> +template <class Payload, class Ignore>
> +struct defer_dtor
> +{
> +public:
> +  typedef Ignore (*dtor_fn) (Payload);
> +  
> +private:
> +  Payload p;
> +  dtor_fn fn;
> +
> +public:
> +  defer_dtor(Payload _p, dtor_fn _fn): p(_p), fn(_fn) {}
> +  ~defer_dtor() { (void) (*fn)(p); }
> +
> +private:
> +  defer_dtor(const defer_dtor<Payload,Ignore>&); // make uncopyable
> +  defer_dtor& operator=(const defer_dtor<Payload,Ignore> &); // make unassignable
> +};
> +
> +

OK. Although my C++ and sqlite knowledge are really not up to date to
really do a proper review.

> +////////////////////////////////////////////////////////////////////////
> +
> +
> +
> +
> +
> +static string
> +conninfo (struct MHD_Connection * conn)
> +{
> +  char hostname[128];
> +  char servname[128];
> +  int sts = -1;
> +
> +  if (conn == 0)
> +    return "internal";
> +
> +  /* Look up client address data. */
> +  const union MHD_ConnectionInfo *u = MHD_get_connection_info (conn,
> +                                                               MHD_CONNECTION_INFO_CLIENT_ADDRESS);
> +  struct sockaddr *so = u ? u->client_addr : 0;
> +
> +  if (so && so->sa_family == AF_INET) {
> +    sts = getnameinfo (so, sizeof (struct sockaddr_in), hostname, sizeof (hostname), servname,
> +                       sizeof (servname), NI_NUMERICHOST | NI_NUMERICSERV);
> +  } else if (so && so->sa_family == AF_INET6) {
> +    sts = getnameinfo (so, sizeof (struct sockaddr_in6), hostname, sizeof (hostname),
> +                       servname, sizeof (servname), NI_NUMERICHOST | NI_NUMERICSERV);
> +  }
> +  if (sts != 0) {
> +    hostname[0] = servname[0] = '\0';
> +  }
> +
> +  return string(hostname) + string(":") + string(servname);
> +}
> +

boo, hardcode name sizes. But ok.

> +
> +////////////////////////////////////////////////////////////////////////
> +
> +static void
> +add_mhd_last_modified (struct MHD_Response *resp, time_t mtime)
> +{
> +  struct tm *now = gmtime (&mtime);
> +  if (now != NULL)
> +    {
> +      char datebuf[80];
> +      size_t rc = strftime (datebuf, sizeof (datebuf), "%a, %d %b %Y %T GMT", now);
> +      if (rc > 0 && rc < sizeof (datebuf))
> +        (void) MHD_add_response_header (resp, "Last-Modified", datebuf);
> +    }
> +  
> +  (void) MHD_add_response_header (resp, "Cache-Control", "public");
> +}

See, here you do use strftime.

> +
> +
> +static struct MHD_Response*
> +handle_buildid_f_match (int64_t b_mtime,
> +                        const string& b_source0,
> +                        int *result_fd)
> +{
> +  int fd = open(b_source0.c_str(), O_RDONLY);
> +  if (fd < 0)
> +    {
> +      if (verbose)
> +        obatched(clog) << "cannot open " << b_source0 << endl;
> +      // if still missing, a periodic groom pass will delete this buildid record
> +      return 0;
> +    }
> +  
> +  // NB: use manual close(2) in error case instead of defer_dtor, because
> +  // in the normal case, we want to hand the fd over to libmicrohttpd for
> +  // file transfer.
> +  
> +  struct stat s;
> +  int rc = fstat(fd, &s);
> +  if (rc < 0)
> +    {
> +      if (verbose)
> +        clog << "cannot fstat " << b_source0 << endl;
> +      close(fd);
> +      return 0;
> +    }
> +
> +  if ((int64_t) s.st_mtime != b_mtime)
> +    {
> +      if (verbose)
> +        obatched(clog) << "mtime mismatch for " << b_source0 << endl;
> +      close(fd);
> +      return 0;
> +    }
> +  
> +  struct MHD_Response* r = MHD_create_response_from_fd ((uint64_t) s.st_size, fd);
> +  if (r == 0)
> +    {
> +      if (verbose)
> +        obatched(clog) << "cannot create fd-response for " << b_source0 << endl;
> +      close(fd);
> +    }
> +  else
> +    {
> +      add_mhd_last_modified (r, s.st_mtime);
> +      if (verbose > 1)
> +        obatched(clog) << "serving file " << b_source0 << endl;
> +      /* libmicrohttpd will close it. */
> +      if (result_fd)
> +        *result_fd = fd;
> +    }
> +
> +  return r;
> +}
> +
> +
> +// quote all questionable characters of str for safe passage through a sh -c expansion.
> +static string
> +shell_escape(const string& str)
> +{
> +  string y;
> +  for (auto&& x : str)
> +    {
> +      if (! isalnum(x) && x != '/')
> +        y += "\\"; 
> +      y += x;
> +    }
> +  return y;
> +}
> +
> +
> +static struct MHD_Response*
> +handle_buildid_r_match (int64_t b_mtime,
> +                        const string& b_source0,
> +                        const string& b_source1,
> +                        int *result_fd)
> +{
> +  struct stat fs;
> +  int rc = stat (b_source0.c_str(), &fs);
> +  if (rc != 0)
> +    throw libc_exception (errno, string("stat ") + b_source0);
> +
> +  if ((int64_t) fs.st_mtime != b_mtime)
> +    {
> +      if (verbose)
> +        obatched(clog) << "mtime mismatch for " << b_source0 << endl;
> +      return 0;
> +    }
> +  
> +  string popen_cmd = string("/usr/bin/rpm2cpio " + shell_escape(b_source0));

Why the hardcoded path?
Could you check at startup if rpm2cpio is in the PATH?

> +  FILE* fp = popen (popen_cmd.c_str(), "r"); // "e" O_CLOEXEC?
> +  if (fp == NULL)
> +    throw libc_exception (errno, string("popen ") + popen_cmd);
> +  defer_dtor<FILE*,int> fp_closer (fp, pclose);
> +
> +  struct archive *a;
> +  a = archive_read_new();
> +  if (a == NULL)
> +    throw archive_exception("cannot create archive reader");
> +  defer_dtor<struct archive*,int> archive_closer (a, archive_read_free);
> +
> +  rc = archive_read_support_format_cpio(a);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot select cpio format");
> +  rc = archive_read_support_filter_all(a);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot select all filters");
> +  
> +  rc = archive_read_open_FILE (a, fp);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot open archive from rpm2cpio pipe");
> +
> +  while(1) // parse cpio archive entries
> +    {
> +      struct archive_entry *e;
> +      rc = archive_read_next_header (a, &e);
> +      if (rc != ARCHIVE_OK)
> +        break;
> +
> +      if (! S_ISREG(archive_entry_mode (e))) // skip non-files completely
> +        continue;
> +              
> +      string fn = archive_entry_pathname (e);
> +      if (fn != string(".")+b_source1)
> +        continue;
> +
> +      // extract this file to a temporary file
> +      char tmppath[PATH_MAX] = "/tmp/debuginfod.XXXXXX"; // XXX: $TMP_DIR etc.

Some other code uses:
  const char *tmpdir = getenv ("TMPDIR") ?: P_tmpdir;
  static const char suffix[] = "/debuginfod.XXXXXX";
Also PATH_MAX?

> +      int fd = mkstemp (tmppath);
> +      if (fd < 0)
> +        throw libc_exception (errno, "cannot create temporary file");
> +      unlink (tmppath); // unlink now so OS will release the file as soon as we close the fd
> +  
> +      rc = archive_read_data_into_fd (a, fd);
> +      if (rc != ARCHIVE_OK)
> +        {
> +          close (fd);
> +          throw archive_exception(a, "cannot extract file");
> +        }
> +
> +      struct MHD_Response* r = MHD_create_response_from_fd (archive_entry_size(e), fd);
> +      if (r == 0)
> +        {
> +          if (verbose)
> +            obatched(clog) << "cannot create fd-response for " << b_source0 << endl;
> +          close(fd);
> +        }

Should this break; ?

Also I prefer checking against NULL, it is slightly more obvious (0
returns  often means success).

> +      else
> +        {
> +          add_mhd_last_modified (r, archive_entry_mtime(e));
> +          if (verbose > 1)
> +            obatched(clog) << "serving rpm " << b_source0 << " file " << b_source1 << endl;
> +          /* libmicrohttpd will close it. */
> +          if (result_fd)
> +            *result_fd = fd;
> +          return r;
> +        }
> +    }
> +
> +  // XXX: rpm/file not found: delete this R entry?
> +  return 0;
> +}

return NULL?
BTW. The usage of "R" or _r_ in the code is slightly confusing. I would
prefer it to just say RPM. Or isn't that what is meant?

> +static struct MHD_Response*
> +handle_buildid_match (int64_t b_mtime,
> +                      const string& b_stype,
> +                      const string& b_source0,
> +                      const string& b_source1,
> +                      int *result_fd)
> +{
> +  if (b_stype == "F")
> +    return handle_buildid_f_match(b_mtime, b_source0, result_fd);
> +  else if (b_stype == "R")
> +    return handle_buildid_r_match(b_mtime, b_source0, b_source1, result_fd);
> +  else
> +    return 0;
> +}
> +
> +
> +
> +static struct MHD_Response* handle_buildid (const string& buildid /* unsafe */,
> +                                            const string& artifacttype /* unsafe */,
> +                                            const string& suffix /* unsafe */,
> +                                            int *result_fd
> +                                            )
> +{
> +  // validate artifacttype
> +  string atype_code;
> +  if (artifacttype == "debuginfo") atype_code = "D";
> +  else if (artifacttype == "executable") atype_code = "E";
> +  else if (artifacttype == "source") atype_code = "S";
> +  else throw reportable_exception("invalid artifacttype");
> +
> +  if (atype_code == "S" && suffix == "")
> +     throw reportable_exception("invalid source suffix");
> +  
> +  // validate buildid
> +  if ((buildid.size() < 2) || // not empty
> +      (buildid.size() % 2) || // even number
> +      (buildid.find_first_not_of("0123456789abcdef") != string::npos)) // pure tasty lowercase hex
> +    throw reportable_exception("invalid buildid");

The % 2 check is good. I don't think we do that everywhere.
The lowercase hex seems a little arbitrary. Maybe first tolower then
check?

> +  if (verbose > 1)
> +    obatched(clog) << "searching for buildid=" << buildid << " artifacttype=" << artifacttype
> +         << " suffix=" << suffix << endl;
> +
> +  sqlite_ps *pp = 0;
> +
> +  if (atype_code == "D")
> +    {
> +      pp = new sqlite_ps (db, "mhd-query-d",
> +                          "select mtime, sourcetype, source0, source1 from " BUILDIDS "_query_d where buildid = ? "
> +                          "order by mtime desc");
> +      pp->reset();
> +      pp->bind(1, buildid);
> +    }
> +  else if (atype_code == "E")
> +    {
> +      pp = new sqlite_ps (db, "mhd-query-e",
> +                          "select mtime, sourcetype, source0, source1 from " BUILDIDS "_query_e where buildid = ? "
> +                          "order by mtime desc");
> +      pp->reset();
> +      pp->bind(1, buildid);
> +    }
> +  else if (atype_code == "S")
> +    {
> +      pp = new sqlite_ps (db, "mhd-query-s",
> +                          "select mtime, sourcetype, source0, source1 from " BUILDIDS "_query_s where buildid = ? and artifactsrc = ? "
> +                          "order by sharedprefix(source0,source0ref) desc, mtime desc");
> +      pp->reset();
> +      pp->bind(1, buildid);
> +      pp->bind(2, suffix);
> +    }
> +  unique_ptr<sqlite_ps> ps_closer(pp); // release pp if exception or return
> +  
> +  // consume all the rows
> +  while (1)
> +    {
> +      int rc = pp->step();
> +      if (rc == SQLITE_DONE) break;
> +      if (rc != SQLITE_ROW)
> +        throw sqlite_exception(rc, "step");
> +      
> +      int64_t b_mtime = sqlite3_column_int64 (*pp, 0);
> +      string b_stype = string((const char*) sqlite3_column_text (*pp, 1) ?: ""); /* by DDL may not be NULL */
> +      string b_source0 = string((const char*) sqlite3_column_text (*pp, 2) ?: ""); /* may be NULL */
> +      string b_source1 = string((const char*) sqlite3_column_text (*pp, 3) ?: ""); /* may be NULL */
> +
> +      if (verbose > 1)
> +        obatched(clog) << "found mtime=" << b_mtime << " stype=" << b_stype
> +             << " source0=" << b_source0 << " source1=" << b_source1 << endl;
> +
> +      // Try accessing the located match.
> +      // XXX: in case of multiple matches, attempt them in parallel?
> +      auto r = handle_buildid_match (b_mtime, b_stype, b_source0, b_source1, result_fd);
> +      if (r)
> +        return r;
> +    }
> +
> +  // We couldn't find it in the database.  Last ditch effort
> +  // is to defer to other debuginfo servers.
> +  int fd = -1;
> +  if (artifacttype == "debuginfo")
> +    fd = debuginfod_find_debuginfo ((const unsigned char*) buildid.c_str(), 0,
> +                                   NULL);
> +  else if (artifacttype == "executable")
> +    fd = debuginfod_find_executable ((const unsigned char*) buildid.c_str(), 0,
> +                                    NULL);
> +  else if (artifacttype == "source")
> +    fd = debuginfod_find_source ((const unsigned char*) buildid.c_str(), 0,
> +                                suffix.c_str(), NULL);
> +  if (fd >= 0)
> +    {
> +      struct stat s;
> +      int rc = fstat (fd, &s);
> +      if (rc == 0)
> +        {
> +          auto r = MHD_create_response_from_fd ((uint64_t) s.st_size, fd);
> +          if (r)
> +            {
> +              add_mhd_last_modified (r, s.st_mtime);
> +              if (verbose > 1)
> +                obatched(clog) << "serving file from upstream debuginfod/cache" << endl;
> +              if (result_fd)
> +                *result_fd = fd;
> +              return r; // NB: don't close fd; libmicrohttpd will
> +            }
> +        }

Shouldn't you handle a failing fstat here?

> +      close (fd);
> +    }
> +  else if (fd != -ENOSYS) // no DEBUGINFOD_URLS configured
> +    throw libc_exception(-fd, "upstream debuginfod query failed");
> +  
> +  throw reportable_exception(MHD_HTTP_NOT_FOUND, "not found");
> +}
> +
> +
> +////////////////////////////////////////////////////////////////////////
> +
> +
> +static struct MHD_Response*
> +handle_metrics ()
> +{
> +  throw reportable_exception("not yet implemented 2");
> +}
> +

Which will come in a later patch.

> +////////////////////////////////////////////////////////////////////////
> +
> +
> +/* libmicrohttpd callback */
> +static int
> +handler_cb (void * /*cls*/,
> +            struct MHD_Connection *connection,
> +            const char *url,
> +            const char *method,
> +            const char * /*version*/,
> +            const char * /*upload_data*/,
> +            size_t * /*upload_data_size*/,
> +            void ** /*con_cls*/)
> +{
> +  struct MHD_Response *r = NULL;
> +  string url_copy = url;
> +  
> +  if (verbose)
> +    obatched(clog) << conninfo(connection) << " " << method << " " << url << endl;
> +
> +  try
> +    {
> +      if (string(method) != "GET")
> +        throw reportable_exception(400, "we support GET only");
> +
> +      /* Start decoding the URL. */
> +      size_t slash1 = url_copy.find('/', 1);
> +      string url1 = url_copy.substr(0, slash1); // ok even if slash1 not found
> +      
> +      if (slash1 != string::npos && url1 == "/buildid")
> +        {
> +          size_t slash2 = url_copy.find('/', slash1+1);
> +          if (slash2 == string::npos)
> +            throw reportable_exception("/buildid/ webapi error, need buildid");
> +          
> +          string buildid = url_copy.substr(slash1+1, slash2-slash1-1);
> +
> +          size_t slash3 = url_copy.find('/', slash2+1);
> +          string artifacttype, suffix;
> +          if (slash3 == string::npos)
> +            {
> +              artifacttype = url_copy.substr(slash2+1);
> +              suffix = "";
> +            }
> +          else
> +            {
> +              artifacttype = url_copy.substr(slash2+1, slash3-slash2-1);
> +              suffix = url_copy.substr(slash3); // include the slash in the suffix
> +            }
> +          
> +          r = handle_buildid(buildid, artifacttype, suffix, 0); // NB: don't care about result-fd
> +        }
> +      else if (url1 == "/metrics")
> +        r = handle_metrics();
> +      else
> +        throw reportable_exception("webapi error, unrecognized /operation");
> +      
> +      if (r == 0)
> +        throw reportable_exception("internal error, missing response");
> +      
> +      int rc = MHD_queue_response (connection, MHD_HTTP_OK, r);
> +      MHD_destroy_response (r);
> +      return rc;
> +    }
> +  catch (const reportable_exception& e)
> +    {
> +      e.report(clog);
> +      return e.mhd_send_response (connection);
> +    }
> +}
> +

OK, as far as I understand the microhttpd stuff.

> +////////////////////////////////////////////////////////////////////////
> +
> +
> +// borrowed from src/nm.c get_local_names()

This is slightly misleading, most of the function is not from there.

> +static void
> +dwarf_extract_source_paths (Elf *elf, set<string>& debug_sourcefiles)
> +  noexcept // no exceptions - so we can simplify the altdbg resource release at end
> +{
> +  Dwarf* dbg = dwarf_begin_elf (elf, DWARF_C_READ, NULL);
> +  if (dbg == NULL)
> +    return;
> +
> +  Dwarf* altdbg = NULL;
> +  int    altdbg_fd = -1;
> +  
> +  // DWZ handling: if we have an unsatisfied debug-alt-link, add an
> +  // empty string into the outgoing sourcefiles set, so the caller 
> +  // should know that our data is incomplete.
> +  const char *alt_name_p;
> +  const void *alt_build_id; // elfutils-owned memory
> +  ssize_t sz = dwelf_dwarf_gnu_debugaltlink (dbg, &alt_name_p, &alt_build_id);
> +  if (sz > 0) // got one!
> +    {
> +      string buildid;
> +      unsigned char* build_id_bytes = (unsigned char*) alt_build_id;
> +      for (ssize_t idx=0; idx<sz; idx++)
> +        {
> +          buildid += "0123456789abcdef"[build_id_bytes[idx] >> 4];
> +          buildid += "0123456789abcdef"[build_id_bytes[idx] & 0xf];
> +        }
> +
> +      if (verbose > 3)
> +        obatched(clog) << "Need altdebug buildid=" << buildid << endl;
> +
> +      // but is it unsatisfied the normal elfutils ways?
> +      Dwarf* alt = dwarf_getalt (dbg);
> +      if (alt == NULL)
> +        {
> +          // Yup, unsatisfied the normal way.  Maybe we can satisfy it
> +          // from our own debuginfod database.
> +          int alt_fd;
> +          struct MHD_Response *r = 0;
> +          try
> +            {
> +              r = handle_buildid (buildid, "debuginfo", "", &alt_fd);
> +            }
> +          catch (const reportable_exception& e)
> +            {
> +              // swallow exceptions
> +            }
> +          
> +          // NB: this is not actually recursive!  This invokes the web-query
> +          // path, which cannot get back into the scan code paths.
> +          if (r)
> +            {
> +              // Found it!
> +              altdbg_fd = dup(alt_fd); // ok if this fails, downstream failures ok
> +              alt = altdbg = dwarf_begin (altdbg_fd, DWARF_C_READ);
> +              // NB: must close this dwarf and this fd at the bottom of the function!
> +              MHD_destroy_response (r); // will close alt_fd
> +              if (alt)
> +                dwarf_setalt (dbg, alt);
> +            }
> +        }
> +      else
> +        {
> +          // NB: dwarf_setalt(alt) inappropriate - already done!
> +          // NB: altdbg will stay 0 so nothing tries to redundantly dealloc.
> +        }
> +      
> +      if (alt)
> +        {
> +          if (verbose > 3)
> +            obatched(clog) << "Resolved altdebug buildid=" << buildid << endl;
> +        }
> +      else // (alt == NULL) - signal possible presence of poor debuginfo
> +        {
> +          debug_sourcefiles.insert("");
> +          if (verbose > 3)
> +            obatched(clog) << "Unresolved altdebug buildid=" << buildid << endl;
> +        }
> +    }

OK. Cute.
  
> +  Dwarf_Off offset = 0;
> +  Dwarf_Off old_offset;
> +  size_t hsize;
> +
> +  while (dwarf_nextcu (dbg, old_offset = offset, &offset, &hsize, NULL, NULL, NULL) == 0)

These days I would prefer dwarf_get_units (). It is slightly higher
level and immediately gives you the cudie and unit_type.

> +    {
> +      Dwarf_Die cudie_mem;
> +      Dwarf_Die *cudie = dwarf_offdie (dbg, old_offset + hsize, &cudie_mem);
> +
> +      if (cudie == NULL)
> +        continue;
> +      if (dwarf_tag (cudie) != DW_TAG_compile_unit)
> +        continue;
> +
> +      const char *cuname = dwarf_diename(cudie) ?: "unknown";
> +
> +      Dwarf_Files *files;
> +      size_t nfiles;
> +      if (dwarf_getsrcfiles (cudie, &files, &nfiles) != 0)
> +        continue;

So you are really only interested in the file/line tables.
In that case you could also use dwarf_next_lines which iterates through
the debug line units directly, so you don't need to do the whole CU DIE
tree iteration yourself (and it handles CUless tables).

> +      // extract DW_AT_comp_dir to resolve relative file names
> +      const char *comp_dir = "";
> +      const char *const *dirs;
> +      size_t ndirs;
> +      if (dwarf_getsrcdirs (files, &dirs, &ndirs) == 0 &&
> +          dirs[0] != NULL)
> +        comp_dir = dirs[0];
> +      if (comp_dir == NULL)
> +        comp_dir = "";
> +      
> +      if (verbose > 3)
> +        obatched(clog) << "searching for sources for cu=" << cuname << " comp_dir=" << comp_dir
> +                       << " #files=" << nfiles << " #dirs=" << ndirs << endl;
> +
> +      if (comp_dir[0] == '\0')
> +        {
> +          // This is a common symptom for dwz-compressed debug files,
> +          // where the altdebug file cannot be resolved.
> +          if (verbose > 3)
> +            obatched(clog) << "skipping cu=" << cuname << " due to empty comp_dir" << endl;
> +          continue;
> +        }
> +
> +      for (size_t f = 1; f < nfiles; f++)
> +        {
> +          const char *hat = dwarf_filesrc (files, f, NULL, NULL);
> +          if (hat == NULL)
> +            continue;
> +
> +          if (string(hat) == "<built-in>") // gcc intrinsics, don't bother record
> +            continue;
> +          
> +          string waldo;
> +          if (hat[0] == '/') // absolute
> +            waldo = (string (hat));
> +          else // comp_dir relative
> +            waldo = (string (comp_dir) + string("/") + string (hat));

Do you have to think about/handle a comp_dir that ends with a / ?
Old debugedit truncated some strings by adding /// (to fill up the
spaces till the '\0'...) Yes, terrible :{
        
> +          // NB: this is the 'waldo' that a dbginfo client will have
> +          // to supply for us to give them the file The comp_dir
> +          // prefixing is a definite complication.  Otherwise we'd
> +          // have to return a setof comp_dirs (one per CU!) with
> +          // corresponding filesrc[] names, instead of one absolute
> +          // resoved set.  Maybe we'll have to do that anyway.  XXX
> +
> +          if (verbose > 4)
> +            obatched(clog) << waldo
> +                           << (debug_sourcefiles.find(waldo)==debug_sourcefiles.end() ? " new" : " dup") <<  endl;
> +          
> +          debug_sourcefiles.insert (waldo);
> +        }
> +    }
> +
> +  dwarf_end(dbg);
> +  if (altdbg)
> +    dwarf_end(altdbg);
> +  if (altdbg_fd >= 0)
> +    close(altdbg_fd);
> +}
> +
> +
> +
> +static void
> +elf_classify (int fd, bool &executable_p, bool &debuginfo_p, string &buildid, set<string>& debug_sourcefiles)
> +{
> +  Elf *elf = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, NULL);
> +  if (elf == NULL)
> +    return;
> +  
> +  try // catch our types of errors and clean up the Elf* object
> +    {
> +      if (elf_kind (elf) != ELF_K_ELF)
> +        {
> +          elf_end (elf);
> +          return;
> +        }
> +
> +      GElf_Ehdr ehdr_storage;
> +      GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_storage);
> +      if (ehdr == NULL)
> +        {
> +          elf_end (elf);
> +          return;
> +        }
> +      auto elf_type = ehdr->e_type;
> +  
> +      const void *build_id; // elfutils-owned memory
> +      ssize_t sz = dwelf_elf_gnu_build_id (elf, & build_id);
> +      if (sz <= 0)
> +        {
> +          // It's not a diagnostic-worthy error for an elf file to lack build-id.
> +          // It might just be very old.
> +          elf_end (elf);
> +          return;
> +        }
> +  
> +      // build_id is a raw byte array; convert to hexadecimal *lowercase*
> +      unsigned char* build_id_bytes = (unsigned char*) build_id;
> +      for (ssize_t idx=0; idx<sz; idx++)
> +        {
> +          buildid += "0123456789abcdef"[build_id_bytes[idx] >> 4];
> +          buildid += "0123456789abcdef"[build_id_bytes[idx] & 0xf];
> +        }
> +
> +      // now decide whether it's an executable - namely, any allocatable section has
> +      // PROGBITS;
> +      if (elf_type == ET_EXEC || elf_type == ET_DYN)
> +        {
> +          size_t shnum;
> +          int rc = elf_getshdrnum (elf, &shnum);
> +          if (rc < 0)
> +            throw elfutils_exception(rc, "getshdrnum");
> +
> +          executable_p = false;
> +          for (size_t sc = 0; sc < shnum; sc++)
> +            {
> +              Elf_Scn *scn = elf_getscn (elf, sc);
> +              if (scn == NULL)
> +                continue;
> +
> +              GElf_Shdr shdr_mem;
> +              GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
> +              if (shdr == NULL)
> +                continue;
> +
> +              // allocated (loadable / vm-addr-assigned) section with available content?
> +              if ((shdr->sh_type == SHT_PROGBITS) && (shdr->sh_flags & SHF_ALLOC))
> +                {
> +                  if (verbose > 4)
> +                    obatched(clog) << "executable due to SHF_ALLOC SHT_PROGBITS sc=" << sc << endl;
> +                  executable_p = true;
> +                  break; // no need to keep looking for others
> +                }
> +            } // iterate over sections
> +        } // executable_p classification

Technically ELF executable files don't have to have sections (shdrs),
only segments (phdrs). Although that is slightly useless.

The above will miss kernel modules (which are ET_REL).

> +      // now decide whether it's a debuginfo - namely, if it has any .debug* or .zdebug* sections
> +      // logic mostly stolen from fweimer@redhat.com's elfclassify drafts
> +      size_t shstrndx;
> +      int rc = elf_getshdrstrndx (elf, &shstrndx);
> +      if (rc < 0)
> +        throw elfutils_exception(rc, "getshdrstrndx");
> +    
> +      Elf_Scn *scn = NULL;
> +      while (true)
> +        {
> +          scn = elf_nextscn (elf, scn);
> +          if (scn == NULL)
> +            break;
> +          GElf_Shdr shdr_storage;
> +          GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_storage);
> +          if (shdr == NULL)
> +            break;
> +          const char *section_name = elf_strptr (elf, shstrndx, shdr->sh_name);
> +          if (section_name == NULL)
> +            break;
> +          if (strncmp(section_name, ".debug_line", 11) == 0 ||
> +              strncmp(section_name, ".zdebug_line", 12) == 0)
> +            {
> +              debuginfo_p = true;
> +              dwarf_extract_source_paths (elf, debug_sourcefiles);
> +              break; // expecting only one .*debug_line, so no need to look for others
> +            }
> +          else if (strncmp(section_name, ".debug_", 7) == 0 ||
> +                   strncmp(section_name, ".zdebug_", 8) == 0)
> +            {
> +              debuginfo_p = true;
> +              // NB: don't break; need to parse .debug_line for sources
> +            }
> +        }
> +    }
> +  catch (const reportable_exception& e)
> +    {
> +      e.report(clog);
> +    }
> +  elf_end (elf);
> +}
> +
> +
> +static semaphore* scan_concurrency_sem = 0; // used to implement -c load limiting
> +
> +
> +static void
> +scan_source_file_path (const string& dir)
> +{
> +  obatched(clog) << "fts/F traversing " << dir << endl;
> +  
> +  struct timeval tv_start, tv_end;
> +  gettimeofday (&tv_start, NULL);
> +  
> +  sqlite_ps ps_upsert_buildids (db, "file-buildids-intern", "insert or ignore into " BUILDIDS "_buildids VALUES (NULL, ?);");
> +  sqlite_ps ps_upsert_files (db, "file-files-intern", "insert or ignore into " BUILDIDS "_files VALUES (NULL, ?);");
> +  sqlite_ps ps_upsert_de (db, "file-de-upsert",
> +                          "insert or ignore into " BUILDIDS "_f_de "
> +                          "(buildid, debuginfo_p, executable_p, file, mtime) "
> +                          "values ((select id from " BUILDIDS "_buildids where hex = ?),"
> +                          "        ?,?,"
> +                          "        (select id from " BUILDIDS "_files where name = ?), ?);");
> +  sqlite_ps ps_upsert_s (db, "file-s-upsert",
> +                         "insert or ignore into " BUILDIDS "_f_s "
> +                         "(buildid, artifactsrc, file, mtime) "
> +                         "values ((select id from " BUILDIDS "_buildids where hex = ?),"
> +                         "        (select id from " BUILDIDS "_files where name = ?),"
> +                         "        (select id from " BUILDIDS "_files where name = ?),"
> +                         "        ?);");
> +  sqlite_ps ps_query (db, "file-negativehit-find",
> +                      "select 1 from " BUILDIDS "_file_mtime_scanned where sourcetype = 'F' and file = (select id from " BUILDIDS "_files where name = ?) and mtime = ?;");
> +  sqlite_ps ps_scan_done (db, "file-scanned",
> +                          "insert or ignore into " BUILDIDS "_file_mtime_scanned (sourcetype, file, mtime, size)"
> +                          "values ('F', (select id from " BUILDIDS "_files where name = ?), ?, ?);");
> +
> +  
> +  char * const dirs[] = { (char*) dir.c_str(), NULL };
> +
> +  unsigned fts_scanned=0, fts_regex=0, fts_cached=0, fts_debuginfo=0, fts_executable=0, fts_sourcefiles=0;
> +  
> +  FTS *fts = fts_open (dirs,
> +                       FTS_PHYSICAL /* don't follow symlinks */
> +                       | FTS_XDEV /* don't cross devices/mountpoints */
> +                       | FTS_NOCHDIR /* multithreaded */,
> +                       NULL);
> +  if (fts == NULL)
> +    {
> +      obatched(cerr) << "cannot fts_open " << dir << endl;
> +      return;
> +    }
> +
> +  FTSENT *f;
> +  while ((f = fts_read (fts)) != NULL)
> +    {
> +      semaphore_borrower handle_one_file (scan_concurrency_sem);
> +      
> +      fts_scanned ++;
> +      if (interrupted)
> +        break;
> +
> +      if (verbose > 2)
> +        obatched(clog) << "fts/F traversing " << f->fts_path << endl;
> +
> +      try
> +        {
> +          /* Found a file.  Convert it to an absolute path, so
> +             the buildid database does not have relative path
> +             names that are unresolvable from a subsequent run
> +             in a different cwd. */
> +          char *rp = realpath(f->fts_path, NULL);
> +          if (rp == NULL)
> +            continue; // ignore dangling symlink or such
> +          string rps = string(rp);
> +          free (rp);
> +
> +          bool ri = !regexec (&file_include_regex, rps.c_str(), 0, 0, 0);
> +          bool rx = !regexec (&file_exclude_regex, rps.c_str(), 0, 0, 0);
> +          if (!ri || rx)
> +            {
> +              if (verbose > 3)
> +                obatched(clog) << "fts/F skipped by regex " << (!ri ? "I" : "") << (rx ? "X" : "") << endl;
> +              fts_regex ++;
> +              continue;
> +            }
> +          
> +          switch (f->fts_info)
> +            {
> +            case FTS_D:
> +              break;
> +
> +            case FTS_DP:
> +              break;
> +
> +            case FTS_F:
> +              {
> +                /* See if we know of it already. */
> +                int rc = ps_query
> +                  .reset()
> +                  .bind(1, rps)
> +                  .bind(2, f->fts_statp->st_mtime)
> +                  .step();
> +                ps_query.reset();
> +                if (rc == SQLITE_ROW) // i.e., a result, as opposed to DONE (no results)
> +                  // no need to recheck a file/version we already know
> +                  // specifically, no need to elf-begin a file we already determined is non-elf
> +                  // (so is stored with buildid=NULL)
> +                  {
> +                    fts_cached ++;
> +                    continue;
> +                  }
> +
> +                bool executable_p = false, debuginfo_p = false; // E and/or D
> +                string buildid;
> +                set<string> sourcefiles;
> +                
> +                int fd = open (rps.c_str(), O_RDONLY);
> +                try
> +                  {
> +                    if (fd >= 0)
> +                      elf_classify (fd, executable_p, debuginfo_p, buildid, sourcefiles);
> +                    else
> +                      throw libc_exception(errno, string("open ") + rps);
> +                  }
> +                
> +                // NB: we catch exceptions from elf_classify here too, so that we can
> +                // cache the corrupt-elf case (!executable_p && !debuginfo_p) just below,
> +                // just as if we had an EPERM error from open(2).
> +                    
> +                catch (const reportable_exception& e)
> +                  {
> +                    e.report(clog);
> +                  }

I think the comment is wrong since elf_classify seems to eat its own
reportable_exceptions (and those thrown from
dwarf_extract_source_paths) because it has its own try catch for
reportable_exceptions and doesn't rethrow them.
                   
> +                if (fd >= 0)
> +                  close (fd);
> +
> +                // register this file name in the interning table
> +                ps_upsert_files
> +                  .reset()
> +                  .bind(1, rps)
> +                  .step_ok_done();
> +                
> +                if (buildid == "")
> +                  {
> +                    // no point storing an elf file without buildid
> +                    executable_p = false;
> +                    debuginfo_p = false;
> +                  }
> +                else
> +                  {
> +                    // register this build-id in the interning table
> +                    ps_upsert_buildids
> +                      .reset()
> +                      .bind(1, buildid)
> +                      .step_ok_done();
> +                  }
> +
> +                if (executable_p)
> +                  fts_executable ++;
> +                if (debuginfo_p)
> +                  fts_debuginfo ++;
> +                if (executable_p || debuginfo_p)
> +                  {
> +                    ps_upsert_de
> +                      .reset()
> +                      .bind(1, buildid)
> +                      .bind(2, debuginfo_p ? 1 : 0)
> +                      .bind(3, executable_p ? 1 : 0)
> +                      .bind(4, rps)
> +                      .bind(5, f->fts_statp->st_mtime)
> +                      .step_ok_done();
> +                  }
> +          
> +                if (sourcefiles.size() && buildid != "")
> +                  {
> +                    fts_sourcefiles += sourcefiles.size();
> +                    
> +                    for (auto&& dwarfsrc : sourcefiles)
> +                      {
> +                        char *srp = realpath(dwarfsrc.c_str(), NULL);
> +                        if (srp == NULL) // also if DWZ unresolved dwarfsrc=""
> +                          continue; // unresolvable files are not a serious problem
> +                        // throw libc_exception(errno, "fts/F realpath " + srcpath);
> +                        string srps = string(srp);
> +                        free (srp);
> +
> +                        struct stat sfs;
> +                        rc = stat(srps.c_str(), &sfs);
> +                        if (rc != 0)
> +                          continue;
> +                      
> +                        if (verbose > 2)
> +                          obatched(clog) << "recorded buildid=" << buildid << " file=" << srps
> +                                         << " mtime=" << sfs.st_mtime
> +                                         << " as source " << dwarfsrc << endl;
> +
> +                        ps_upsert_files
> +                          .reset()
> +                          .bind(1, srps)
> +                          .step_ok_done();
> +
> +                        // register the dwarfsrc name in the interning table too
> +                        ps_upsert_files
> +                          .reset()
> +                          .bind(1, dwarfsrc)
> +                          .step_ok_done();
> +
> +                        ps_upsert_s
> +                          .reset()
> +                          .bind(1, buildid)
> +                          .bind(2, dwarfsrc)
> +                          .bind(3, srps)
> +                          .bind(4, sfs.st_mtime)
> +                          .step_ok_done();
> +                      }
> +                  }
> +
> +                ps_scan_done
> +                  .reset()
> +                  .bind(1, rps)
> +                  .bind(2, f->fts_statp->st_mtime)
> +                  .bind(3, f->fts_statp->st_size)
> +                  .step_ok_done();
> +                
> +                if (verbose > 2)
> +                  obatched(clog) << "recorded buildid=" << buildid << " file=" << rps
> +                                 << " mtime=" << f->fts_statp->st_mtime << " atype="
> +                                 << (executable_p ? "E" : "")
> +                                 << (debuginfo_p ? "D" : "") << endl;
> +              }
> +              break;
> +
> +            case FTS_ERR:
> +            case FTS_NS:
> +              throw libc_exception(f->fts_errno, string("fts/F traversal ") + string(f->fts_path));
> +
> +            default:
> +            case FTS_SL: /* NB: don't enter symbolic links into the database */
> +              break;
> +            }
> +
> +          if ((verbose && f->fts_info == FTS_DP) ||
> +              (verbose > 1 && f->fts_info == FTS_F))
> +            obatched(clog) << "fts/F traversing " << rps << ", scanned=" << fts_scanned
> +                 << ", regex-skipped=" << fts_regex
> +                 << ", cached=" << fts_cached << ", debuginfo=" << fts_debuginfo
> +                 << ", executable=" << fts_executable << ", source=" << fts_sourcefiles << endl;
> +        }
> +      catch (const reportable_exception& e)
> +        {
> +          e.report(clog);
> +        }
> +    }
> +  fts_close (fts);
> +
> +  gettimeofday (&tv_end, NULL);
> +  double deltas = (tv_end.tv_sec - tv_start.tv_sec) + (tv_end.tv_usec - tv_start.tv_usec)*0.000001;
> +  
> +  obatched(clog) << "fts/F traversed " << dir << " in " << deltas << "s, scanned=" << fts_scanned
> +                 << ", regex-skipped=" << fts_regex
> +                 << ", cached=" << fts_cached << ", debuginfo=" << fts_debuginfo
> +                 << ", executable=" << fts_executable << ", source=" << fts_sourcefiles << endl;
> +}

OK.

> +static void*
> +thread_main_scan_source_file_path (void* arg)
> +{
> +  string dir = string((const char*) arg);
> +
> +  unsigned rescan_timer = 0;
> +  sig_atomic_t forced_rescan_count = 0;
> +  while (! interrupted)
> +    {
> +      try
> +        {
> +          if (rescan_timer == 0)
> +            scan_source_file_path (dir);
> +          else if (sigusr1 != forced_rescan_count)
> +            {
> +              forced_rescan_count = sigusr1;
> +              scan_source_file_path (dir);              
> +            }
> +        }
> +      catch (const sqlite_exception& e)
> +        {
> +          obatched(cerr) << e.message << endl;
> +        }
> +      sleep (1);
> +      rescan_timer ++;
> +      if (rescan_s)
> +        rescan_timer %= rescan_s;
> +    }
> +  
> +  return 0;
> +}

Can we use something nicer than the hardcode sleep (1) ?

> +
> +////////////////////////////////////////////////////////////////////////
> +
> +
> +
> +
> +// Analyze given *.rpm file of given age; record buildids / exec/debuginfo-ness of its
> +// constituent files with given upsert statements.
> +static void
> +rpm_classify (const string& rps, sqlite_ps& ps_upsert_buildids, sqlite_ps& ps_upsert_files,
> +              sqlite_ps& ps_upsert_de, sqlite_ps& ps_upsert_sref, sqlite_ps& ps_upsert_sdef,
> +              time_t mtime,
> +              unsigned& fts_executable, unsigned& fts_debuginfo, unsigned& fts_sref, unsigned& fts_sdef,
> +              bool& fts_sref_complete_p)
> +{
> +  string popen_cmd = string("/usr/bin/rpm2cpio " + shell_escape(rps));

Another hard coded rpm2cpio path...

> +  FILE* fp = popen (popen_cmd.c_str(), "r"); // "e" O_CLOEXEC?
> +  if (fp == NULL)
> +    throw libc_exception (errno, string("popen ") + popen_cmd);
> +  defer_dtor<FILE*,int> fp_closer (fp, pclose);
> +
> +  struct archive *a;
> +  a = archive_read_new();
> +  if (a == NULL)
> +    throw archive_exception("cannot create archive reader");
> +  defer_dtor<struct archive*,int> archive_closer (a, archive_read_free);
> +
> +  int rc = archive_read_support_format_cpio(a);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot select cpio format");
> +  rc = archive_read_support_filter_all(a);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot select all filters");
> +  
> +  rc = archive_read_open_FILE (a, fp);
> +  if (rc != ARCHIVE_OK)
> +    throw archive_exception(a, "cannot open archive from rpm2cpio pipe");
> +
> +  if (verbose > 3)
> +    obatched(clog) << "rpm2cpio|libarchive scanning " << rps << endl;
> +  
> +  while(1) // parse cpio archive entries
> +    {
> +      try
> +        {
> +          struct archive_entry *e;
> +          rc = archive_read_next_header (a, &e);
> +          if (rc != ARCHIVE_OK)
> +            break;
> +
> +          if (! S_ISREG(archive_entry_mode (e))) // skip non-files completely
> +            continue;
> +              
> +          string fn = archive_entry_pathname (e);
> +          if (fn.size() > 1 && fn[0] == '.')
> +            fn = fn.substr(1); // trim off the leading '.'
> +          
> +          if (verbose > 3)
> +            obatched(clog) << "rpm2cpio|libarchive checking " << fn << endl;
> +
> +          // extract this file to a temporary file
> +          char tmppath[PATH_MAX] = "/tmp/debuginfod.XXXXXX"; // XXX: $TMP_DIR etc.
> +          int fd = mkstemp (tmppath);
> +          if (fd < 0)
> +            throw libc_exception (errno, "cannot create temporary file");
> +          unlink (tmppath); // unlink now so OS will release the file as soon as we close the fd
> +          defer_dtor<int,int> minifd_closer (fd, close);
> +  
> +          rc = archive_read_data_into_fd (a, fd);
> +          if (rc != ARCHIVE_OK)
> +            throw archive_exception(a, "cannot extract file");
> +
> +          // finally ... time to run elf_classify on this bad boy and update the database
> +          bool executable_p = false, debuginfo_p = false;
> +          string buildid;
> +          set<string> sourcefiles;
> +          elf_classify (fd, executable_p, debuginfo_p, buildid, sourcefiles);
> +          // NB: might throw
> +
> +          if (buildid != "") // intern buildid
> +            {
> +              ps_upsert_buildids
> +                .reset()
> +                .bind(1, buildid)
> +                .step_ok_done();
> +            }
> +
> +          ps_upsert_files // register this rpm constituent file name in interning table
> +            .reset()
> +            .bind(1, fn)
> +            .step_ok_done();
> +          
> +          if (sourcefiles.size() > 0) // sref records needed
> +            {
> +              // NB: we intern each source file once.  Once raw, as it
> +              // appears in the DWARF file list coming back from
> +              // elf_classify() - because it'll end up in the
> +              // _norm.artifactsrc column.  We don't also put another
> +              // version with a '.' at the front, even though that's
> +              // how rpm/cpio packs names, because we hide that from
> +              // the database for storage efficiency.
> +
> +              for (auto&& s : sourcefiles)
> +                {
> +                  if (s == "")
> +                    {
> +                      fts_sref_complete_p = false;
> +                      continue;
> +                    }
> +                  
> +                  ps_upsert_files
> +                    .reset()
> +                    .bind(1, s)
> +                    .step_ok_done();
> +
> +                  ps_upsert_sref
> +                    .reset()
> +                    .bind(1, buildid)
> +                    .bind(2, s)
> +                    .step_ok_done();
> +
> +                  fts_sref ++;
> +                }
> +            }
> +
> +          if (executable_p)
> +            fts_executable ++;
> +          if (debuginfo_p)
> +            fts_debuginfo ++;
> +
> +          if (executable_p || debuginfo_p)
> +            {          
> +              ps_upsert_de
> +                .reset()
> +                .bind(1, buildid)
> +                .bind(2, debuginfo_p ? 1 : 0)
> +                .bind(3, executable_p ? 1 : 0)
> +                .bind(4, rps)
> +                .bind(5, mtime)
> +                .bind(6, fn)
> +                .step_ok_done();
> +            }
> +          else // potential source - sdef record
> +            {
> +              fts_sdef ++;
> +              ps_upsert_sdef
> +                .reset()
> +                .bind(1, rps)
> +                .bind(2, mtime)
> +                .bind(3, fn)
> +                .step_ok_done();
> +            }
> +          
> +          if ((verbose > 2) && (executable_p || debuginfo_p))
> +            obatched(clog) << "recorded buildid=" << buildid << " rpm=" << rps << " file=" << fn
> +                           << " mtime=" << mtime << " atype="
> +                           << (executable_p ? "E" : "")
> +                           << (debuginfo_p ? "D" : "")
> +                           << " sourcefiles=" << sourcefiles.size() << endl;
> +          
> +        }
> +      catch (const reportable_exception& e)
> +        {
> +          e.report(clog);
> +        }
> +    }
> +}
> +
> +
> +
> +// scan for *.rpm files
> +static void
> +scan_source_rpm_path (const string& dir)
> +{
> +  obatched(clog) << "fts/R traversing " << dir << endl;
> +    
> +  sqlite_ps ps_upsert_buildids (db, "rpm-buildid-intern", "insert or ignore into " BUILDIDS "_buildids VALUES (NULL, ?);");
> +  sqlite_ps ps_upsert_files (db, "rpm-file-intern", "insert or ignore into " BUILDIDS "_files VALUES (NULL, ?);");
> +  sqlite_ps ps_upsert_de (db, "rpm-de-insert",
> +                          "insert or ignore into " BUILDIDS "_r_de (buildid, debuginfo_p, executable_p, file, mtime, content) values ("
> +                          "(select id from " BUILDIDS "_buildids where hex = ?), ?, ?, "
> +                          "(select id from " BUILDIDS "_files where name = ?), ?, "
> +                          "(select id from " BUILDIDS "_files where name = ?));");
> +  sqlite_ps ps_upsert_sref (db, "rpm-sref-insert",
> +                            "insert or ignore into " BUILDIDS "_r_sref (buildid, artifactsrc) values ("
> +                            "(select id from " BUILDIDS "_buildids where hex = ?), "
> +                            "(select id from " BUILDIDS "_files where name = ?));");
> +  sqlite_ps ps_upsert_sdef (db, "rpm-sdef-insert",
> +                            "insert or ignore into " BUILDIDS "_r_sdef (file, mtime, content) values ("
> +                            "(select id from " BUILDIDS "_files where name = ?), ?,"
> +                            "(select id from " BUILDIDS "_files where name = ?));");
> +  // XXX: _r_dalt

What?

> +  sqlite_ps ps_query (db, "rpm-negativehit-query",
> +                      "select 1 from " BUILDIDS "_file_mtime_scanned where "
> +                      "sourcetype = 'R' and file = (select id from " BUILDIDS "_files where name = ?) and mtime = ?;");
> +  sqlite_ps ps_scan_done (db, "rpm-scanned",
> +                          "insert or ignore into " BUILDIDS "_file_mtime_scanned (sourcetype, file, mtime, size)"
> +                          "values ('R', (select id from " BUILDIDS "_files where name = ?), ?, ?);");
> +
> +  char * const dirs[] = { (char*) dir.c_str(), NULL };
> +
> +  struct timeval tv_start, tv_end;
> +  gettimeofday (&tv_start, NULL);
> +  unsigned fts_scanned=0, fts_regex=0, fts_cached=0, fts_debuginfo=0;
> +  unsigned fts_executable=0, fts_rpm = 0, fts_sref=0, fts_sdef=0;
> +  
> +  FTS *fts = fts_open (dirs,
> +                       FTS_PHYSICAL /* don't follow symlinks */
> +                       | FTS_XDEV /* don't cross devices/mountpoints */
> +                       | FTS_NOCHDIR /* multithreaded */,
> +                       NULL);
> +  if (fts == NULL)
> +    {
> +      obatched(cerr) << "cannot fts_open " << dir << endl;
> +      return;
> +    }
> +
> +  FTSENT *f;
> +  while ((f = fts_read (fts)) != NULL)
> +    {
> +      semaphore_borrower handle_one_file (scan_concurrency_sem);
> +
> +      fts_scanned ++;
> +      if (interrupted)
> +        break;
> +
> +      if (verbose > 2)
> +        obatched(clog) << "fts/R traversing " << f->fts_path << endl;
> +
> +      try
> +        {
> +          /* Found a file.  Convert it to an absolute path, so
> +             the buildid database does not have relative path
> +             names that are unresolvable from a subsequent run
> +             in a different cwd. */
> +          char *rp = realpath(f->fts_path, NULL);
> +          if (rp == NULL)
> +            continue; // ignore dangling symlink or such
> +          string rps = string(rp);
> +          free (rp);
> +
> +          bool ri = !regexec (&file_include_regex, rps.c_str(), 0, 0, 0);
> +          bool rx = !regexec (&file_exclude_regex, rps.c_str(), 0, 0, 0);
> +          if (!ri || rx)
> +            {
> +              if (verbose > 3)
> +                obatched(clog) << "fts/R skipped by regex " << (!ri ? "I" : "") << (rx ? "X" : "") << endl;
> +              fts_regex ++;
> +              continue;
> +            }
> +
> +          switch (f->fts_info)
> +            {
> +            case FTS_D:
> +              break;
> +
> +            case FTS_DP:
> +              break;
> +
> +            case FTS_F:
> +              {
> +                // heuristic: reject if file name does not end with ".rpm"
> +                // (alternative: try opening with librpm etc., caching)
> +                string suffix = ".rpm";
> +                if (rps.size() < suffix.size() ||
> +                    rps.substr(rps.size()-suffix.size()) != suffix)
> +                  continue;
> +                fts_rpm ++;
> +                
> +                /* See if we know of it already. */
> +                int rc = ps_query
> +                  .reset()
> +                  .bind(1, rps)
> +                  .bind(2, f->fts_statp->st_mtime)
> +                  .step();
> +                ps_query.reset();                
> +                if (rc == SQLITE_ROW) // i.e., a result, as opposed to DONE (no results)
> +                  // no need to recheck a file/version we already know
> +                  // specifically, no need to parse this rpm again, since we already have
> +                  // it as a D or E or S record, 
> +                  // (so is stored with buildid=NULL)
> +                  {
> +                    fts_cached ++;
> +                    continue;
> +                  }
> +
> +                // intern the rpm file name
> +                ps_upsert_files
> +                  .reset()
> +                  .bind(1, rps)
> +                  .step_ok_done();
> +                
> +                // extract the rpm contents via popen("rpm2cpio") | libarchive | loop-of-elf_classify()
> +                unsigned my_fts_executable = 0, my_fts_debuginfo = 0, my_fts_sref = 0, my_fts_sdef = 0;
> +                bool my_fts_sref_complete_p = true;
> +                try
> +                  {
> +                    rpm_classify (rps,
> +                                  ps_upsert_buildids, ps_upsert_files,
> +                                  ps_upsert_de, ps_upsert_sref, ps_upsert_sdef, // dalt
> +                                  f->fts_statp->st_mtime,
> +                                  my_fts_executable, my_fts_debuginfo, my_fts_sref, my_fts_sdef,
> +                                  my_fts_sref_complete_p);
> +                  }
> +                catch (const reportable_exception& e)
> +                  {
> +                    e.report(clog);
> +                  }
> +
> +                if (verbose > 2)
> +                  obatched(clog) << "scanned rpm=" << rps
> +                                 << " mtime=" << f->fts_statp->st_mtime
> +                                 << " executables=" << my_fts_executable
> +                                 << " debuginfos=" << my_fts_debuginfo
> +                                 << " srefs=" << my_fts_sref
> +                                 << " sdefs=" << my_fts_sdef
> +                                 << endl;
> + 
> +                if (0)  // XXX: if unsatisfied debugalt set is non-empty ...:
> +                  break;

What?

> +                fts_executable += my_fts_executable;
> +                fts_debuginfo += my_fts_debuginfo;
> +                fts_sref += my_fts_sref;
> +                fts_sdef += my_fts_sdef;
> +
> +                if (my_fts_sref_complete_p) // leave incomplete?
> +                  ps_scan_done
> +                    .reset()
> +                    .bind(1, rps)
> +                    .bind(2, f->fts_statp->st_mtime)
> +                    .bind(3, f->fts_statp->st_size)
> +                    .step_ok_done();
> +              }
> +              break;
> +
> +            case FTS_ERR:
> +            case FTS_NS:
> +              throw libc_exception(f->fts_errno, string("fts/R traversal ") + string(f->fts_path));
> +
> +            default:
> +            case FTS_SL: /* NB: don't enter symbolic links into the database */
> +              break;
> +            }
> +
> +          if ((verbose && f->fts_info == FTS_DP) ||
> +              (verbose > 1 && f->fts_info == FTS_F))
> +            obatched(clog) << "fts/R traversing " << rps << ", scanned=" << fts_scanned
> +                           << ", regex-skipped=" << fts_regex
> +                           << ", rpm=" << fts_rpm << ", cached=" << fts_cached << ", debuginfo=" << fts_debuginfo
> +                           << ", executable=" << fts_executable
> +                           << ", sourcerefs=" << fts_sref << ", sourcedefs=" << fts_sdef << endl;
> +        }
> +      catch (const reportable_exception& e)
> +        {
> +          e.report(clog);
> +        }
> +    }
> +  fts_close (fts);
> +
> +  gettimeofday (&tv_end, NULL);
> +  double deltas = (tv_end.tv_sec - tv_start.tv_sec) + (tv_end.tv_usec - tv_start.tv_usec)*0.000001;
> +  
> +  obatched(clog) << "fts/R traversed " << dir << " in " << deltas << "s, scanned=" << fts_scanned
> +                 << ", regex-skipped=" << fts_regex
> +                 << ", rpm=" << fts_rpm << ", cached=" << fts_cached << ", debuginfo=" << fts_debuginfo
> +                 << ", executable=" << fts_executable
> +                 << ", sourcerefs=" << fts_sref << ", sourcedefs=" << fts_sdef << endl;
> +}
> +
> +
> +
> +static void*
> +thread_main_scan_source_rpm_path (void* arg)
> +{
> +  string dir = string((const char*) arg);
> +
> +  unsigned rescan_timer = 0;
> +  sig_atomic_t forced_rescan_count = 0;
> +  while (! interrupted)
> +    {
> +      try
> +        {
> +          if (rescan_timer == 0)
> +            scan_source_rpm_path (dir);
> +          else if (sigusr1 != forced_rescan_count)
> +            {
> +              forced_rescan_count = sigusr1;
> +              scan_source_rpm_path (dir);              
> +            }
> +        }
> +      catch (const sqlite_exception& e)
> +        {
> +          obatched(cerr) << e.message << endl;
> +        }
> +      sleep (1);
> +      rescan_timer ++;
> +      if (rescan_s)
> +        rescan_timer %= rescan_s;
> +    }
> +
> +  return 0;
> +}

OK, but that sleep (1) is bugging me.

> +
> +////////////////////////////////////////////////////////////////////////
> +
> +static void
> +database_stats_report()
> +{
> +  sqlite_ps ps_query (db, "database-overview",
> +                      "select label,quantity from " BUILDIDS "_stats");
> +
> +  obatched(clog) << "database record counts:" << endl;
> +  while (1)
> +    {
> +      int rc = sqlite3_step (ps_query);
> +      if (rc == SQLITE_DONE) break;
> +      if (rc != SQLITE_ROW)
> +        throw sqlite_exception(rc, "step");
> +
> +      obatched(clog)
> +        << right << setw(20) << ((const char*) sqlite3_column_text(ps_query, 0) ?: (const char*) "NULL")
> +        << " "
> +        << (sqlite3_column_text(ps_query, 1) ?: (const unsigned char*) "NULL")
> +        << endl;
> +    }
> +}
> +
> +
> +// Do a round of database grooming that might take many minutes to run.
> +void groom()
> +{
> +  obatched(clog) << "grooming database" << endl;
> +  
> +  struct timeval tv_start, tv_end;
> +  gettimeofday (&tv_start, NULL);
> +  
> +  // scan for files that have disappeared
> +  sqlite_ps files (db, "check old files", "select s.mtime, s.file, f.name from "
> +                       BUILDIDS "_file_mtime_scanned s, " BUILDIDS "_files f "
> +                       "where f.id = s.file");
> +  sqlite_ps files_del_f_de (db, "nuke f_de", "delete from " BUILDIDS "_f_de where file = ? and mtime = ?");
> +  sqlite_ps files_del_r_de (db, "nuke r_de", "delete from " BUILDIDS "_r_de where file = ? and mtime = ?");
> +  sqlite_ps files_del_scan (db, "nuke f_m_s", "delete from " BUILDIDS "_file_mtime_scanned "
> +                            "where file = ? and mtime = ?");
> +  files.reset();
> +  while(1)
> +    {
> +      int rc = files.step();
> +      if (rc != SQLITE_ROW)
> +        break;
> +      
> +      int64_t mtime = sqlite3_column_int64 (files, 0);
> +      int64_t fileid = sqlite3_column_int64 (files, 1);
> +      const char* filename = ((const char*) sqlite3_column_text (files, 2) ?: "");
> +      struct stat s;
> +      rc = stat(filename, &s);
> +      if (rc < 0 || (mtime != (int64_t) s.st_mtime))
> +        {
> +          if (verbose > 2)
> +            obatched(clog) << "groom: forgetting file=" << filename << " mtime=" << mtime << endl;
> +          files_del_f_de.reset().bind(1,fileid).bind(2,mtime).step_ok_done();
> +          files_del_r_de.reset().bind(1,fileid).bind(2,mtime).step_ok_done();
> +          files_del_scan.reset().bind(1,fileid).bind(2,mtime).step_ok_done();
> +        }
> +    }
> +  files.reset();
> +
> +  // delete buildids with no references in _r_de or _f_de tables;
> +  // cascades to _r_sref & _f_s records
> +  sqlite_ps buildids_del (db, "nuke orphan buildids",
> +                          "delete from " BUILDIDS "_buildids "
> +                          "where not exists (select 1 from " BUILDIDS "_f_de d where " BUILDIDS "_buildids.id = d.buildid) "
> +                          "and not exists (select 1 from " BUILDIDS "_r_de d where " BUILDIDS "_buildids.id = d.buildid)");
> +  buildids_del.reset().step_ok_done();
> +  
> +  // NB: "vacuum" is too heavy for even daily runs: it rewrites the entire db, so is done as maxigroom -G
> +  sqlite_ps g1 (db, "incremental vacuum", "pragma incremental_vacuum");
> +  g1.reset().step_ok_done();
> +  sqlite_ps g2 (db, "optimize", "pragma optimize");
> +  g2.reset().step_ok_done();
> +  sqlite_ps g3 (db, "wal checkpoint", "pragma wal_checkpoint=truncate");
> +  g3.reset().step_ok_done();
> +
> +  database_stats_report();
> +  
> +  gettimeofday (&tv_end, NULL);
> +  double deltas = (tv_end.tv_sec - tv_start.tv_sec) + (tv_end.tv_usec - tv_start.tv_usec)*0.000001;
> +
> +  obatched(clog) << "groomed database in " << deltas << "s" << endl;
> +}

OK, I assume.

> +
> +static void*
> +thread_main_groom (void* /*arg*/)
> +{
> +  unsigned groom_timer = 0;
> +  sig_atomic_t forced_groom_count = 0;
> +  while (! interrupted)
> +    {
> +      try
> +        {
> +          if (groom_timer == 0)
> +            groom ();
> +          else if (sigusr2 != forced_groom_count)
> +            {
> +              forced_groom_count = sigusr2;
> +              groom ();
> +            }
> +        }
> +      catch (const sqlite_exception& e)
> +        {
> +          obatched(cerr) << e.message << endl;
> +        }
> +      sleep (1);
> +      groom_timer ++;
> +      if (groom_s)
> +        groom_timer %= groom_s;
> +    }
> +
> +  return 0;
> +}

Again that hard coded sleep (1).
Can't it actually wait groom_s seconds?
It seems you are waiting for an interrupt and a signal handler would
make sleep () return early.

> +
> +////////////////////////////////////////////////////////////////////////
> +
> +
> +static void
> +signal_handler (int /* sig */)
> +{
> +  interrupted ++;
> +
> +  if (db)
> +    sqlite3_interrupt (db);
> +  
> +  // NB: don't do anything else in here
> +}

Nothing ever sets db to NULL after sqlite3_open.
The documentation of sqlite3_interrupt says:

"it is not safe to call this routine with a database connection that is
closed or might close before sqlite3_interrupt() returns"

So it seems this might cause trouble when this is called just
before/while sqlite3_close (db) is being called.

> +static void
> +sigusr1_handler (int /* sig */)
> +{
> +   sigusr1 ++;
> +  // NB: don't do anything else in here
> +}
> +
> +static void
> +sigusr2_handler (int /* sig */)
> +{
> +   sigusr2 ++;
> +  // NB: don't do anything else in here
> +}

OK

> +// A user-defined sqlite function, to score the sharedness of the
> +// prefix of two strings.  This is used to compare candidate debuginfo
> +// / source-rpm names, so that the closest match
> +// (directory-topology-wise closest) is found.  This is important in
> +// case the same sref (source file name) is in many -debuginfo or
> +// -debugsource RPMs, such as when multiple versions/releases of the
> +// same package are in the database.
> +
> +static void sqlite3_sharedprefix_fn (sqlite3_context* c, int argc, sqlite3_value** argv)
> +{
> +  if (argc != 2)
> +    sqlite3_result_error(c, "expect 2 string arguments", -1);
> +  else if ((sqlite3_value_type(argv[0]) != SQLITE_TEXT) ||
> +           (sqlite3_value_type(argv[1]) != SQLITE_TEXT))
> +    sqlite3_result_null(c);
> +  else
> +    {
> +      const unsigned char* a = sqlite3_value_text (argv[0]);
> +      const unsigned char* b = sqlite3_value_text (argv[1]);
> +      int i = 0;
> +      while (*a++ == *b++)
> +        i++;
> +      sqlite3_result_int (c, i);
> +    }
> +}

Assuming OK.

> +int
> +main (int argc, char *argv[])
> +{
> +  (void) setlocale (LC_ALL, "");
> +  (void) bindtextdomain (PACKAGE_TARNAME, LOCALEDIR);
> +  (void) textdomain (PACKAGE_TARNAME);
> +
> +  /* Tell the library which version we are expecting.  */
> +  elf_version (EV_CURRENT);
> +  
> +  /* Set computed default values. */
> +  db_path = string(getenv("HOME") ?: "/") + string("/.debuginfod.sqlite"); /* XDG? */
> +  int rc = regcomp (& file_include_regex, ".*", REG_EXTENDED|REG_NOSUB); // match everything
> +  if (rc != 0)
> +    error (EXIT_FAILURE, 0, "regcomp failure: %d", rc);
> +  rc = regcomp (& file_exclude_regex, "^$", REG_EXTENDED|REG_NOSUB); // match nothing
> +  if (rc != 0)
> +    error (EXIT_FAILURE, 0, "regcomp failure: %d", rc);
> +  
> +  /* Parse and process arguments.  */
> +  int remaining;
> +  argp_program_version_hook = print_version; // this works
> +  (void) argp_parse (&argp, argc, argv, ARGP_IN_ORDER, &remaining, NULL);
> +  if (remaining != argc)
> +      error (EXIT_FAILURE, 0,
> +             "unexpected argument: %s", argv[remaining]);
> +    
> +  (void) signal (SIGPIPE, SIG_IGN); // microhttpd can generate it incidentally, ignore
> +  (void) signal (SIGINT, signal_handler); // ^C
> +  (void) signal (SIGHUP, signal_handler); // EOF
> +  (void) signal (SIGTERM, signal_handler); // systemd
> +  (void) signal (SIGUSR1, sigusr1_handler); // end-user
> +  (void) signal (SIGUSR2, sigusr2_handler); // end-user
> +  
> +  // do this before any threads start
> +  scan_concurrency_sem = new semaphore(concurrency);
> +  
> +  /* Get database ready. */
> +  rc = sqlite3_open_v2 (db_path.c_str(), &db, (SQLITE_OPEN_READWRITE
> +                                               |SQLITE_OPEN_CREATE
> +                                               |SQLITE_OPEN_FULLMUTEX), /* thread-safe */
> +                        NULL);
> +  if (rc == SQLITE_CORRUPT)
> +    {
> +      (void) unlink (db_path.c_str());
> +      error (EXIT_FAILURE, 0,
> +             "cannot open %s, deleted database: %s", db_path.c_str(), sqlite3_errmsg(db));
> +    }
> +  else if (rc)
> +    {
> +      error (EXIT_FAILURE, 0,
> +             "cannot open %s, database: %s", db_path.c_str(), sqlite3_errmsg(db));
> +    }
> +
> +  obatched(clog) << "opened database " << db_path << endl;
> +  obatched(clog) << "sqlite version " << sqlite3_version << endl;
> +
> +  // add special string-prefix-similarity function used in rpm sref/sdef resolution
> +  rc = sqlite3_create_function(db, "sharedprefix", 2, SQLITE_UTF8, NULL,
> +                               & sqlite3_sharedprefix_fn, NULL, NULL);
> +  if (rc != SQLITE_OK)
> +    error (EXIT_FAILURE, 0,
> +           "cannot create sharedprefix( function: %s", sqlite3_errmsg(db));
> +  
> +  if (verbose > 3)
> +    obatched(clog) << "ddl: " << DEBUGINFOD_SQLITE_DDL << endl;
> +  rc = sqlite3_exec (db, DEBUGINFOD_SQLITE_DDL, NULL, NULL, NULL);
> +  if (rc != SQLITE_OK)
> +    {
> +      error (EXIT_FAILURE, 0,
> +             "cannot run database schema ddl: %s", sqlite3_errmsg(db));
> +    }
> +
> +  // Start httpd server threads.  Separate pool for IPv4 and IPv6, in
> +  // case the host only has one protocol stack.
> +  MHD_Daemon *d4 = MHD_start_daemon (MHD_USE_THREAD_PER_CONNECTION
> +#if MHD_VERSION >= 0x00095300
> +                                     | MHD_USE_INTERNAL_POLLING_THREAD
> +#else
> +                                     | MHD_USE_SELECT_INTERNALLY
> +#endif
> +                                     | MHD_USE_DEBUG, /* report errors to stderr */
> +                                     http_port,
> +                                     NULL, NULL, /* default accept policy */
> +                                     handler_cb, NULL, /* handler callback */
> +                                     MHD_OPTION_END);
> +  MHD_Daemon *d6 = MHD_start_daemon (MHD_USE_THREAD_PER_CONNECTION
> +#if MHD_VERSION >= 0x00095300
> +                                     | MHD_USE_INTERNAL_POLLING_THREAD
> +#else
> +                                     | MHD_USE_SELECT_INTERNALLY
> +#endif
> +                                     | MHD_USE_IPv6
> +                                     | MHD_USE_DEBUG, /* report errors to stderr */
> +                                     http_port,
> +                                     NULL, NULL, /* default accept policy */
> +                                     handler_cb, NULL, /* handler callback */
> +                                     MHD_OPTION_END);
> +
> +  if (d4 == NULL && d6 == NULL) // neither ipv4 nor ipv6? boo
> +    {
> +      sqlite3_close (db);
> +      error (EXIT_FAILURE, 0, "cannot start http server at port %d", http_port);
> +    }
> +
> +  obatched(clog) << "started http server on "
> +                 << (d4 != NULL ? "IPv4 " : "")
> +                 << (d6 != NULL ? "IPv6 " : "")
> +                 << "port=" << http_port << endl;
> +
> +  // add maxigroom sql if -G given
> +  if (maxigroom)
> +    {
> +      obatched(clog) << "maxigrooming database, please wait." << endl;
> +      extra_ddl.push_back("create index if not exists " BUILDIDS "_r_sref_arc on " BUILDIDS "_r_sref(artifactsrc);");
> +      extra_ddl.push_back("delete from " BUILDIDS "_r_sdef where not exists (select 1 from " BUILDIDS "_r_sref b where " BUILDIDS "_r_sdef.content = b.artifactsrc);");
> +      extra_ddl.push_back("drop index if exists " BUILDIDS "_r_sref_arc;");
> +      
> +      // NB: we don't maxigroom the _files interning table.  It'd require a temp index on all the
> +      // tables that have file foreign-keys, which is a lot.
> +
> +      // NB: with =delete, may take up 3x disk space total during vacuum process
> +      //     vs.  =off (only 2x but may corrupt database if program dies mid-vacuum)
> +      //     vs.  =wal (>3x observed, but safe)
> +      extra_ddl.push_back("pragma journal_mode=delete;");
> +      extra_ddl.push_back("vacuum;");
> +      extra_ddl.push_back("pragma journal_mode=wal;");
> +    }
> +  
> +  // run extra -D sql if given
> +  for (auto&& i: extra_ddl)
> +    {
> +      if (verbose > 1)
> +        obatched(clog) << "extra ddl:\n" << i << endl;
> +      rc = sqlite3_exec (db, i.c_str(), NULL, NULL, NULL);
> +      if (rc != SQLITE_OK && rc != SQLITE_DONE && rc != SQLITE_ROW)
> +        error (0, 0,
> +               "warning: cannot run database extra ddl %s: %s", i.c_str(), sqlite3_errmsg(db));
> +    }
> +  
> +  if (maxigroom)
> +    obatched(clog) << "maxigroomed database" << endl;
> +
> +      
> +  obatched(clog) << "search concurrency " << concurrency << endl;
> +  obatched(clog) << "rescan time " << rescan_s << endl;
> +  obatched(clog) << "groom time " << groom_s << endl;
> +  
> +  vector<pthread_t> source_file_scanner_threads;
> +  vector<pthread_t> source_rpm_scanner_threads;
> +  pthread_t groom_thread;
> +
> +  rc = pthread_create (& groom_thread, NULL, thread_main_groom, NULL);
> +  if (rc < 0)
> +    error (0, 0, "warning: cannot spawn thread (%d) to groom database\n", rc);
> + 
> +  for (auto&& it : source_paths)
> +    {
> +      pthread_t pt;
> +      rc = pthread_create (& pt, NULL, thread_main_scan_source_file_path, (void*) it.c_str());
> +      if (rc < 0)
> +        error (0, 0, "warning: cannot spawn thread (%d) to scan source files %s\n", rc, it.c_str());
> +      else
> +        source_file_scanner_threads.push_back(pt);
> +    }
> +
> +  for (auto&& it : source_paths)
> +    {
> +      pthread_t pt;
> +      rc = pthread_create (& pt, NULL, thread_main_scan_source_rpm_path, (void*) it.c_str());
> +      if (rc < 0)
> +        error (0, 0, "warning: cannot spawn thread (%d) to scan source rpms %s\n", rc, it.c_str());
> +      else
> +        source_rpm_scanner_threads.push_back(pt);
> +    }
> +
> +  
> +  const char* du = getenv(DEBUGINFOD_URLS_ENV_VAR);
> +  if (du && du[0] != '\0') // set to non-empty string?
> +    obatched(clog) << "upstream debuginfod servers: " << du << endl;
> +  
> +  /* Trivial main loop! */
> +  while (! interrupted)
> +    pause ();
> +
> +  if (verbose)
> +    obatched(clog) << "stopping" << endl;
> +  
> +  /* Stop all the web service threads. */
> +  if (d4) MHD_stop_daemon (d4);
> +  if (d6) MHD_stop_daemon (d6);
> +  
> +  /* Join any source scanning threads. */
> +  for (auto&& it : source_file_scanner_threads)
> +    pthread_join (it, NULL);
> +  for (auto&& it : source_rpm_scanner_threads)
> +    pthread_join (it, NULL);
> +  pthread_join (groom_thread, NULL);
> +      
> +  /* With all threads known dead, we can clean up the global resources. */
> +  delete scan_concurrency_sem;
> +  rc = sqlite3_exec (db, DEBUGINFOD_SQLITE_CLEANUP_DDL, NULL, NULL, NULL);
> +  if (rc != SQLITE_OK)
> +    {
> +      error (0, 0,
> +             "warning: cannot run database cleanup ddl: %s", sqlite3_errmsg(db));
> +    }
> +
> +  (void) sqlite3_close (db);
> +  // NB: no problem with unconditional free here - an earlier failed regcomp would exit program
> +  (void) regfree (& file_include_regex);
> +  (void) regfree (& file_exclude_regex);
> +  
> +  return 0;
> +}

OK


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