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Re: RFA: Fix a big memory leak reading minimal symbols
- From: Elena Zannoni <ezannoni at redhat dot com>
- To: Daniel Jacobowitz <drow at mvista dot com>
- Cc: Elena Zannoni <ezannoni at redhat dot com>, gdb-patches at sources dot redhat dot com
- Date: Wed, 19 Feb 2003 16:24:39 -0500
- Subject: Re: RFA: Fix a big memory leak reading minimal symbols
- References: <20030126191411.GA1824@nevyn.them.org><15937.26495.326748.558348@localhost.redhat.com><20030205222626.GA28452@nevyn.them.org>
Daniel Jacobowitz writes:
> On Wed, Feb 05, 2003 at 02:35:27PM -0500, Elena Zannoni wrote:
> > Daniel Jacobowitz writes:
> > > 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.
> >
> > right, elfstab_build_psymtab is called by elf_symfile_read, after
> > init_minimal_symbol_collection.
> >
> > > - dbx_symfile_read contains a complete init_minimal_symbol_collection /
> > > install_minimal_symbols pair, which generally finds no minimal symbols
> > > in ELF.
> >
> > elfstab_build_psymtab calls dbx_symfile_read.
> >
> > > - install_minimal_symbols and matching cleanup in elf_symfile_read.
> > >
> >
> > at the end.
> >
> > > 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.
> >
> > OK, I see the problem in this sequence. There is another 'stray' call
> > to install_minimal_symbols, in stabsect_build_psymtab, and this
> > function also calls dbx_symfile_read. The sequence is the same. So the
> > problem should occur there as well.
> > stabsect_build_psymtab is called by som_symfile_read.
>
> And by nlm_symfile_read too.
>
> > > 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.
> >
> > How does elfstab_build_psymtabs get invoked from mdebug? Oh, it
> > doesn't. It gets invoked after the mdebug stuff is over.
> >
> > I see, you are adding pairs of install+cleanup to the mdebug psymtab
> > builder, i.e. each piece is self-sufficient. For the stabs psymtab
> > builder the appropriate steps are done in dbx_symfile_read already.
>
> Right. Each reader that wants to do this, should do it itself, since
> they don't nest.
>
> > let's see all the symtabs builders:
> >
> > coffstab_build_psymtabs -> calls dbx_symfile_read ok
>
> Ugh. This is OK but its caller isn't; coff_symtab_read has some
> minimal symbols outstanding when it calls coffstab_build_psymtabs.
> Fixed, but I don't have any tests for COFF set up.
>
> > elfstab_build_psymtabs -> you fixed ok
> > stabsect_build_psymtabs -> dubious
>
> Fixed, in both callers.
>
> > dwarf2_build_psymtabs -> no need
> > dwarf_build_psymtabs -> don't care
> > hpread_build_psymtabs -> no clue, messy. I think it does it directly.
> > mdebug_build_psymtabs -> you fixed ok
> >
> > if the table above makes sense, then can you verify/fix the dubious case?
>
> How's this look? New changes in coff_symfile_read, nlm_symfile_read,
> som_symfile_read, and stabsect_build_psymtabs.
>
Okey
elena
> --
> Daniel Jacobowitz
> MontaVista Software Debian GNU/Linux Developer
>
> 2002-02-05 Daniel Jacobowitz <drow at mvista dot com>
>
> * coffread.c (coff_symfile_read): Clean up minimal symbols earlier.
> * dbxread.c (elfstab_build_psymtabs): Don't call
> install_minimal_symbols.
> (stabsect_build_psymtabs): Likewise.
> * elfread.c (elf_symfile_read): Call install_minimal_symbols
> earlier.
> * somread.c (som_symfile_read): Call install_minimal_symbols
> and do_cleanups earlier.
> * nlmread.c (nlm_symfile_read): Likewise.
> * mdebugread.c (elfmdebug_build_psymtabs): Call
> install_minimal_symbols and make appropriate cleanups.
>
> Index: coffread.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/coffread.c,v
> retrieving revision 1.33
> diff -u -p -r1.33 coffread.c
> --- coffread.c 4 Feb 2003 18:07:00 -0000 1.33
> +++ coffread.c 5 Feb 2003 22:22:13 -0000
> @@ -515,7 +515,7 @@ coff_symfile_read (struct objfile *objfi
> unsigned int num_symbols;
> int symtab_offset;
> int stringtab_offset;
> - struct cleanup *back_to;
> + struct cleanup *back_to, *cleanup_minimal_symbols;
> int stabstrsize;
> int len;
> char * target;
> @@ -595,7 +595,7 @@ coff_symfile_read (struct objfile *objfi
> error ("\"%s\": can't get string table", name);
>
> init_minimal_symbol_collection ();
> - make_cleanup_discard_minimal_symbols ();
> + cleanup_minimal_symbols = make_cleanup_discard_minimal_symbols ();
>
> /* Now that the executable file is positioned at symbol table,
> process it and define symbols accordingly. */
> @@ -615,6 +615,9 @@ coff_symfile_read (struct objfile *objfi
> minimal symbols for this objfile. */
>
> install_minimal_symbols (objfile);
> +
> + /* Free the installed minimal symbol data. */
> + do_cleanups (cleanup_minimal_symbols);
>
> bfd_map_over_sections (abfd, coff_locate_sections, (void *) info);
>
> Index: dbxread.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dbxread.c,v
> retrieving revision 1.41
> diff -u -p -r1.41 dbxread.c
> --- dbxread.c 31 Jan 2003 19:22:17 -0000 1.41
> +++ dbxread.c 5 Feb 2003 22:22:13 -0000
> @@ -3555,7 +3555,6 @@ elfstab_build_psymtabs (struct objfile *
> buildsym_new_init ();
> free_header_files ();
> init_header_files ();
> - install_minimal_symbols (objfile);
>
> processing_acc_compilation = 1;
>
> @@ -3567,7 +3566,10 @@ elfstab_build_psymtabs (struct objfile *
>
> /* 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);
>
> if (back_to)
> @@ -3649,7 +3651,6 @@ stabsect_build_psymtabs (struct objfile
> buildsym_new_init ();
> free_header_files ();
> init_header_files ();
> - install_minimal_symbols (objfile);
>
> /* Now, do an incremental load */
>
> Index: elfread.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/elfread.c,v
> retrieving revision 1.30
> diff -u -p -r1.30 elfread.c
> --- elfread.c 31 Jan 2003 19:22:18 -0000 1.30
> +++ elfread.c 5 Feb 2003 22:22:14 -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. */
>
> @@ -611,13 +620,6 @@ 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: /cvs/src/src/gdb/mdebugread.c,v
> retrieving revision 1.40
> diff -u -p -r1.40 mdebugread.c
> --- mdebugread.c 4 Feb 2003 18:07:01 -0000 1.40
> +++ mdebugread.c 5 Feb 2003 22:22:15 -0000
> @@ -4808,6 +4808,14 @@ 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,
> @@ -4818,6 +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);
> }
>
>
> Index: nlmread.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/nlmread.c,v
> retrieving revision 1.9
> diff -u -p -r1.9 nlmread.c
> --- nlmread.c 2 Dec 2001 22:38:23 -0000 1.9
> +++ nlmread.c 5 Feb 2003 22:22:15 -0000
> @@ -190,6 +190,12 @@ nlm_symfile_read (struct objfile *objfil
>
> nlm_symtab_read (abfd, offset, 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);
> +
> stabsect_build_psymtabs (objfile, mainline, ".stab",
> ".stabstr", ".text");
>
> @@ -204,13 +210,6 @@ nlm_symfile_read (struct objfile *objfil
>
> /* FIXME: We could locate and read the optional native debugging format
> here and add the symbols to the minimal symbol table. */
> -
> - /* Install any minimal symbols that have been collected as the current
> - minimal symbols for this objfile. */
> -
> - install_minimal_symbols (objfile);
> -
> - do_cleanups (back_to);
> }
>
>
> Index: somread.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/somread.c,v
> retrieving revision 1.16
> diff -u -p -r1.16 somread.c
> --- somread.c 19 Jan 2003 04:06:46 -0000 1.16
> +++ somread.c 5 Feb 2003 22:22:15 -0000
> @@ -353,6 +353,14 @@ som_symfile_read (struct objfile *objfil
>
> som_symtab_read (abfd, objfile, objfile->section_offsets);
>
> + /* Install any minimal symbols that have been collected as the current
> + minimal symbols for this objfile.
> + Further symbol-reading is done incrementally, file-by-file,
> + in a step known as "psymtab-to-symtab" expansion. hp-symtab-read.c
> + contains the code to do the actual DNTT scanning and symtab building. */
> + install_minimal_symbols (objfile);
> + do_cleanups (back_to);
> +
> /* Now read information from the stabs debug sections.
> This is a no-op for SOM.
> Perhaps it is intended for some kind of mixed STABS/SOM
> @@ -366,16 +374,8 @@ som_symfile_read (struct objfile *objfil
> together with a scan of the GNTT. See hp-psymtab-read.c. */
> hpread_build_psymtabs (objfile, mainline);
>
> - /* Install any minimal symbols that have been collected as the current
> - minimal symbols for this objfile.
> - Further symbol-reading is done incrementally, file-by-file,
> - in a step known as "psymtab-to-symtab" expansion. hp-symtab-read.c
> - contains the code to do the actual DNTT scanning and symtab building. */
> - install_minimal_symbols (objfile);
> -
> /* Force hppa-tdep.c to re-read the unwind descriptors. */
> objfile->obj_private = NULL;
> - do_cleanups (back_to);
> }
>
> /* Initialize anything that needs initializing when a completely new symbol