Re: crash/regression with ia64 targets

[Joel Brobecker <brobecker at adacore dot com>]

> I wonder why this crash wasn't visible before.  AFAICS from find_sym_fns,
> the only kinds of objfiles that can be loaded without debugging symbols are
> srec, ihex and tekhex (the latter can have symbols, but we don't read
> in those).
> 
> Ah, indeed, it was.  I can reproduce it:

Nice! (I think)

> Not clear to me which place would be best.  I suggest do nothing,
> as its easiest  :-)

Sold :)

Attached is the patch I am currently testing. It already passed
testing on ia64-linux (ie: I reverted the patch triggering the
crash, ran the testsuite, then un-reverted it, and applied this
patch), no regression. It passesd testing on x64_64-linux as well.

Testing on x86_64-darwin is under way, and I will add ppc-aix and
x86-windows using AdaCore's testsuite.

But given the nature of the changes triggering the cross-platform
testing, I remain fairly confident of the results.

gdb/ChangeLog:

        * symfile.c (syms_from_objfile_1): Renames syms_from_objfile.
        Remove call to init_entry_point_info.  Add OBJFILE's
        section_offsets and num_sections initialization.  Add note
        about entry info in the function documentation.
        (syms_from_objfile): New function.
        * coffread.c (coff_symfile_init): Remove call to
        init_entry_point_info.
        * machoread.c (macho_symfile_init): Likewise.
        * xcoffread.c(xcoff_symfile_init): Likewise.

Thanks,
-- 
Joel

>From b1508860e512c1d9ee1c9826d1df5b1990af8230 Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Fri, 14 Dec 2012 01:25:26 -0500
Subject: [PATCH] Fix NULL objfile's section_offsets dereference during symbol load.

gdb/ChangeLog:

        * symfile.c (syms_from_objfile_1): Renames syms_from_objfile.
        Remove call to init_entry_point_info.  Add OBJFILE's
        section_offsets and num_sections initialization.  Add note
        about entry info in the function documentation.
        (syms_from_objfile): New function.
        * coffread.c (coff_symfile_init): Remove call to
        init_entry_point_info.
        * machoread.c (macho_symfile_init): Likewise.
        * xcoffread.c(xcoff_symfile_init): Likewise.
---
 gdb/coffread.c  |    2 --
 gdb/machoread.c |    1 -
 gdb/symfile.c   |   42 ++++++++++++++++++++++++++++++++++--------
 gdb/xcoffread.c |    2 --
 4 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/gdb/coffread.c b/gdb/coffread.c
index 56ed5ae..398e61c 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -469,8 +469,6 @@ coff_symfile_init (struct objfile *objfile)
      find this causes a significant slowdown in gdb then we could
      set it in the debug symbol readers only when necessary.  */
   objfile->flags |= OBJF_REORDERED;
-
-  init_entry_point_info (objfile);
 }
 
 /* This function is called for every section; it finds the outer
diff --git a/gdb/machoread.c b/gdb/machoread.c
index 6a6eaa1..c0e6d90 100644
--- a/gdb/machoread.c
+++ b/gdb/machoread.c
@@ -79,7 +79,6 @@ static void
 macho_symfile_init (struct objfile *objfile)
 {
   objfile->flags |= OBJF_REORDERED;
-  init_entry_point_info (objfile);
 }
 
 /*  Add a new OSO to the vector of OSO to load.  */
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 6e09cbd..2a15293 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -896,6 +896,8 @@ read_symbols (struct objfile *objfile, int add_flags)
 /* Process a symbol file, as either the main file or as a dynamically
    loaded file.
 
+   This function does not set the OBJFILE's entry-point info.
+
    OBJFILE is where the symbols are to be read from.
 
    ADDRS is the list of section load addresses.  If the user has given
@@ -923,12 +925,12 @@ read_symbols (struct objfile *objfile, int add_flags)
    an extra symbol file such as dynamically loaded code, and wether
    breakpoint reset should be deferred.  */
 
-void
-syms_from_objfile (struct objfile *objfile,
-                   struct section_addr_info *addrs,
-                   struct section_offsets *offsets,
-                   int num_offsets,
-		   int add_flags)
+static void
+syms_from_objfile_1 (struct objfile *objfile,
+		     struct section_addr_info *addrs,
+		     struct section_offsets *offsets,
+		     int num_offsets,
+		     int add_flags)
 {
   struct section_addr_info *local_addr = NULL;
   struct cleanup *old_chain;
@@ -936,11 +938,21 @@ syms_from_objfile (struct objfile *objfile,
 
   gdb_assert (! (addrs && offsets));
 
-  init_entry_point_info (objfile);
   objfile->sf = find_sym_fns (objfile->obfd);
 
   if (objfile->sf == NULL)
-    return;	/* No symbols.  */
+    {
+      /* No symbols to load, but we still need to make sure
+	 that the section_offsets table is allocated.  */
+      int num_sections = bfd_count_sections (objfile->obfd);
+      size_t size = SIZEOF_N_SECTION_OFFSETS (num_offsets);
+
+      objfile->num_sections = num_sections;
+      objfile->section_offsets
+        = obstack_alloc (&objfile->objfile_obstack, size);
+      memset (objfile->section_offsets, 0, size);
+      return;
+    }
 
   /* Make sure that partially constructed symbol tables will be cleaned up
      if an error occurs during symbol reading.  */
@@ -1021,6 +1033,20 @@ syms_from_objfile (struct objfile *objfile,
   xfree (local_addr);
 }
 
+/* Same as syms_from_objfile_1, but also initializes the objfile
+   entry-point info.  */
+
+void
+syms_from_objfile (struct objfile *objfile,
+		   struct section_addr_info *addrs,
+		   struct section_offsets *offsets,
+		   int num_offsets,
+		   int add_flags)
+{
+  syms_from_objfile_1 (objfile, addrs, offsets, num_offsets, add_flags);
+  init_entry_point_info (objfile);
+}
+
 /* Perform required actions after either reading in the initial
    symbols for a new objfile, or mapping in the symbols from a reusable
    objfile.  ADD_FLAGS is a bitmask of enum symfile_add_flags.  */
diff --git a/gdb/xcoffread.c b/gdb/xcoffread.c
index ee47f6c..10c93cc 100644
--- a/gdb/xcoffread.c
+++ b/gdb/xcoffread.c
@@ -1922,8 +1922,6 @@ xcoff_symfile_init (struct objfile *objfile)
      find this causes a significant slowdown in gdb then we could
      set it in the debug symbol readers only when necessary.  */
   objfile->flags |= OBJF_REORDERED;
-
-  init_entry_point_info (objfile);
 }
 
 /* Perform any local cleanups required when we are done with a particular
-- 
1.7.0.4