[binutils-gdb] Fix regression caused by minimal symbol changes

[Tom Tromey <tromey at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4bd56d18cc9799f283715a96ba61fd4b958b2f71

commit 4bd56d18cc9799f283715a96ba61fd4b958b2f71
Author: Tom Tromey <tromey@adacore.com>
Date:   Mon Mar 18 09:32:09 2019 -0600

    Fix regression caused by minimal symbol changes
    
    The earlier patch to change minimal symbol allocations to use xmalloc
    erroneously left a call to obstack_blank in
    minimal_symbol_reader::install.  Because obstack_blank does not finish
    the object allocation on an obstack, this in turn could cause invalid
    memory reads in some situations.
    
    This patch fixes the problem by removing the call.  Tested on x86-64
    Fedora 29; also verified with valgrind.
    
    gdb/ChangeLog
    2019-03-18  Tom Tromey  <tromey@adacore.com>
    
    	* minsyms.c (minimal_symbol_reader::install): Remove call to
    	obstack_blank.

Diff:
---
 gdb/ChangeLog | 5 +++++
 gdb/minsyms.c | 2 --
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d23819d..b224ebd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2019-03-18  Tom Tromey  <tromey@adacore.com>
+
+	* minsyms.c (minimal_symbol_reader::install): Remove call to
+	obstack_blank.
+
 2019-03-18  Pedro Alves  <palves@redhat.com>
 
 	* tui/tui-io.c (reverse_mode_p, reverse_save_bg, reverse_save_fg):
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index fe2ad94..b95e9ef 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -1360,8 +1360,6 @@ minimal_symbol_reader::install ()
          we will give back the excess space.  */
 
       alloc_count = m_msym_count + m_objfile->per_bfd->minimal_symbol_count;
-      obstack_blank (&m_objfile->per_bfd->storage_obstack,
-		     alloc_count * sizeof (struct minimal_symbol));
       gdb::unique_xmalloc_ptr<minimal_symbol>
 	msym_holder (XNEWVEC (minimal_symbol, alloc_count));
       msymbols = msym_holder.get ();