Re: [PATCH] Add --print-dirs option for ldconfig

[Dan Nicholson <dbn dot lists at gmail dot com>]

On Fri, May 11, 2012 at 05:57:09AM -0700, Dan Nicholson wrote:
> On Mon, Apr 02, 2012 at 05:35:07PM -0700, Dan Nicholson wrote:
> > On Mon, Apr 02, 2012 at 11:14:19AM -0700, Roland McGrath wrote:
> > > Exactly what uses is this intended for?  
> > 
> > Figuring out where the linker is looking for libraries since it's not
> > really documented anywhere.
> > 
> > > It shows all the directories listed in configuration files.  It
> > > doesn't show all the directories that ldconfig searches.  That's
> > > because the hwcap-named subdirectories don't get added until inside
> > > the same loop that finds the individual libraries.  So if the intent
> > > is to list all the directories where ldconfig might find libraries,
> > > then it needs more work.
> > 
> > Right, I'd forgotten about those since they don't really get used on
> > Fedora. I took another look and did the print at the time the
> > directory is added to the list. It seems to work correctly now, but
> > it's not as clean since you actually have to let it build up the cache
> > to find all the directories. Untangling that seemed way too intrusive,
> > though.
> > 
> > Doing this change did highlight a couple things to me, though.
> > 
> > * The non-existent directories won't be shown. It could be nice to
> >   know all the possible directories, but didn't seem ncessary.
> > 
> > * The path built up by ldconfig puts the hwcap directories at the end.
> >   I would have expected them to come at the beginning like
> >   LD_DEBUG=libs shows. It does seem that things work out correctly in
> >   the cache, though.
> > 
> > Anyway, updated patch attached.
> 
> OK, that patch sucked. After spending more time looking at this
> (especially the hwcap paths), I think it's important to decide what this
> feature should do.
> 
> 1. Print just the base directories or the hwcap subdirectories, too? The
>    latter can additionally confusing because ldconfig will recursively
>    join hwcap entries as it finds them. From what I can tell, ld.so does
>    not perform that feature.
> 
> 2. Print the directories that are requested to be searched or just the
>    ones that actually exist?
> 
> On this iteration, I've decided to optionally add the hwcap subdirs (not
> recursively) and print the directories as requested. Here is sample
> output from a Fedora 16 x86_64 system:
> 
> $ ./elf/ldconfig -P
> /usr/lib64/atlas
> /usr/lib64/llvm
> /usr/lib64/tracker-0.12
> /usr/lib64/xulrunner-2
> /lib
> /lib64
> /libx32
> /usr/lib
> /usr/lib64
> /usr/libx32
> 
> When -v|--verbose is added, the hwcap entries will be appended as
> subdirs.
> 
> $ ./elf/ldconfig -Pv
> /usr/lib64/atlas/sse2
> /usr/lib64/atlas/i386
> /usr/lib64/atlas/i486
> /usr/lib64/atlas/i586
> /usr/lib64/atlas/i686
> /usr/lib64/atlas/tls
> /usr/lib64/atlas
> ...
> 
> I had to more or less duplicate some code to do this without entering a
> major refactoring. The difference here is that I'm iterating over all
> known hwcap entries, but the cache building code looks at each entry and
> checks if it's a hwcap. Roland, what do you think?

Sorry, scratch that one. I still had some asprintfs in there from when I
was actually filling in the dir_entry for each hwcap path.

2012-05-11  Dan Nicholson  <dbn.lists@gmail.com>

	* elf/ldconfig.c (opt_print_search_dirs): New variable.
	(options, parse_opt): Add -P|--print-search-dirs to set it.
	(add_dir): Print directories when set. Print hwcap subdirs when
	opt_verbose set.
	(main): Exit after adding directories when option set.
---
 elf/ldconfig.c |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/elf/ldconfig.c b/elf/ldconfig.c
index aa97213..cdffcf5 100644
--- a/elf/ldconfig.c
+++ b/elf/ldconfig.c
@@ -89,6 +89,9 @@ static struct dir_entry *dir_entries;
 /* Print Cache.  */
 static int opt_print_cache;
 
+/* Print search directories.  */
+static int opt_print_search_dirs;
+
 /* Be verbose.  */
 int opt_verbose;
 
@@ -138,6 +141,7 @@ static char *more_help (int key, const char *text, void *input);
 static const struct argp_option options[] =
 {
   { "print-cache", 'p', NULL, 0, N_("Print cache"), 0},
+  { "print-search-dirs", 'P', NULL, 0, N_("Print search directories"), 0},
   { "verbose", 'v', NULL, 0, N_("Generate verbose messages"), 0},
   { NULL, 'N', NULL, 0, N_("Don't build cache"), 0},
   { NULL, 'X', NULL, 0, N_("Don't generate links"), 0},
@@ -266,6 +270,9 @@ parse_opt (int key, char *arg, struct argp_state *state)
     case 'p':
       opt_print_cache = 1;
       break;
+    case 'P':
+      opt_print_search_dirs = 1;
+      break;
     case 'r':
       opt_chroot = arg;
       break;
@@ -395,6 +402,37 @@ add_dir (const char *line)
   if (i == 0)
     return;
 
+  /* Don't bother stating if we're just printing the search path */
+  if (opt_print_search_dirs)
+    {
+      /* Append the hwcap entries when verbose. */
+      if (opt_verbose)
+	{
+	  /* Find all the hwcap subdirectories. */
+	  for (int hwcap_idx = 0; hwcap_idx < _DL_HWCAP_COUNT; ++hwcap_idx)
+	      if ((1ULL << hwcap_idx) & hwcap_mask)
+		printf ("%s/%s\n", entry->path, _dl_hwcap_string (hwcap_idx));
+
+#ifdef _DL_FIRST_PLATFORM
+	  /* Find all the platform subdirectories. */
+	  for (int plat_idx = _DL_FIRST_PLATFORM; plat_idx < _DL_FIRST_EXTRA;
+	       ++plat_idx)
+	    printf ("%s/%s\n", entry->path, _dl_platform_string (plat_idx));
+#endif /* _DL_FIRST_PLATFORM */
+
+	  /* Extra hwcap directories */
+	  for (int hwcap_idx = _DL_FIRST_EXTRA; hwcap_idx < 64; ++hwcap_idx)
+	    if (hwcap_extra[hwcap_idx - _DL_FIRST_EXTRA] != NULL)
+	      printf ("%s/%s\n", entry->path,
+		      hwcap_extra[hwcap_idx - _DL_FIRST_EXTRA]);
+	}
+
+      puts (entry->path);
+      free (entry->path);
+      free (entry);
+      return;
+    }
+
   char *path = entry->path;
   if (opt_chroot)
     path = chroot_canon (opt_chroot, path);
@@ -1359,6 +1397,10 @@ main (int argc, char **argv)
 	add_system_dir (LIBDIR);
     }
 
+  /* Search path printed in add_dir () */
+  if (opt_print_search_dirs)
+    exit (0);
+
   const char *aux_cache_file = _PATH_LDCONFIG_AUX_CACHE;
   if (opt_chroot)
     aux_cache_file = chroot_canon (opt_chroot, aux_cache_file);
-- 
1.7.7.6