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 --git a/gdb/ChangeLog b/gdb/ChangeLog
index d23819d..b224ebd 100644 (file)
--- 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 (file)
--- 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 ();