RFA: Fix a big memory leak reading minimal symbols

[Daniel Jacobowitz]

This patch is good for a whopping 13% (7MB) of memory usage when reading in
all of mozilla's minimal symbols (stabs).  The control flow looks like this
right now:
  - init_minimal_symbol_collection in elf_symfile_read
  - install_minimal_symbols in elfstab_build_psymtabs.  Presumably added so
    that we don't lose the minimal symbols above.
  - dbx_symfile_read contains a complete init_minimal_symbol_collection /
    install_minimal_symbols pair, which generally finds no minimal symbols
    in ELF.
  - install_minimal_symbols and matching cleanup in elf_symfile_read.

Only problem is, that second init_minimal_symbol_collection call zeroed out
the bunch pointer.  We've installed them but we never free them, so they
just sit around wasting memory.

This patch arranges for all calls to init_minimal_symbol_collection in ELF
targets to be paired with matching cleanups and install_minimal_symbols
calls.  This means that elfmdebug_build_psymtabs gets its own pair instead
of relying on elf_symfile_read, and that elf_symfile_read installs its own
minimal symbols much earlier.

I'd like a symtab maintainer to look over this patch; the more eyes the
better.  I'm probably also short some copyright dates; I'll get them when/if
I check it in.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2002-01-26  Daniel Jacobowitz  <drow@mvista.com>

	* dbxread.c (elfstab_build_psymtabs): Don't call
	install_minimal_symbols.
	* elfread.c (elf_symfile_read): Call install_minimal_symbols
	earlier.
	* mdebugread.c (elfmdebug_build_psymtabs): Call
	install_minimal_symbols and make appropriate cleanups.

Index: dbxread.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/dbxread.c,v
retrieving revision 1.40
diff -u -p -r1.40 dbxread.c
--- dbxread.c	18 Jan 2003 15:55:51 -0000	1.40
+++ dbxread.c	22 Jan 2003 23:19:29 -0000
@@ -3511,13 +3511,16 @@ elfstab_build_psymtabs (struct objfile *
   buildsym_new_init ();
   free_header_files ();
   init_header_files ();
-  install_minimal_symbols (objfile);
 
   processing_acc_compilation = 1;
 
   /* In an elf file, we've already installed the minimal symbols that came
      from the elf (non-stab) symbol table, so always act like an
-     incremental load here. */
+     incremental load here.  dbx_symfile_read should not generate any new
+     minimal symbols, since we will have already read the ELF dynamic symbol
+     table and normal symbol entries won't be in the ".stab" section; but in
+     case it does, it will install them itself.  */
+
   dbx_symfile_read (objfile, 0);
 }
 
Index: elfread.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/elfread.c,v
retrieving revision 1.29
diff -u -p -r1.29 elfread.c
--- elfread.c	14 Jan 2003 00:49:03 -0000	1.29
+++ elfread.c	22 Jan 2003 23:16:02 -0000
@@ -542,6 +542,15 @@ elf_symfile_read (struct objfile *objfil
 
   elf_symtab_read (objfile, 1);
 
+  /* Install any minimal symbols that have been collected as the current
+     minimal symbols for this objfile.  The debug readers below this point
+     should not generate new minimal symbols; if they do it's their
+     responsibility to install them.  "mdebug" appears to be the only one
+     which will do this.  */
+
+  install_minimal_symbols (objfile);
+  do_cleanups (back_to);
+
   /* Now process debugging information, which is contained in
      special ELF sections. */
 
@@ -612,13 +621,6 @@ elf_symfile_read (struct objfile *objfil
 
   if (DWARF2_BUILD_FRAME_INFO_P ())
     DWARF2_BUILD_FRAME_INFO(objfile);
-
-  /* Install any minimal symbols that have been collected as the current
-     minimal symbols for this objfile. */
-
-  install_minimal_symbols (objfile);
-
-  do_cleanups (back_to);
 }
 
 /* This cleans up the objfile's sym_stab_info pointer, and the chain of
Index: mdebugread.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/mdebugread.c,v
retrieving revision 1.39
diff -u -p -r1.39 mdebugread.c
--- mdebugread.c	18 Jan 2003 15:55:52 -0000	1.39
+++ mdebugread.c	26 Jan 2003 17:01:39 -0000
@@ -4810,6 +4810,14 @@ elfmdebug_build_psymtabs (struct objfile
 {
   bfd *abfd = objfile->obfd;
   struct ecoff_debug_info *info;
+  struct cleanup *back_to;
+
+  /* FIXME: It's not clear whether we should be getting minimal symbol
+     information from .mdebug in an ELF file, or whether we will.
+     Re-initialize the minimal symbol reader in case we do.  */
+
+  init_minimal_symbol_collection ();
+  back_to = make_cleanup_discard_minimal_symbols ();
 
   info = ((struct ecoff_debug_info *)
 	  obstack_alloc (&objfile->psymbol_obstack,
@@ -4820,6 +4826,9 @@ elfmdebug_build_psymtabs (struct objfile
 	   bfd_errmsg (bfd_get_error ()));
 
   mdebug_build_psymtabs (objfile, swap, info);
+
+  install_minimal_symbols (objfile);
+  do_cleanups (back_to);
 }