[patch] Fix ASAN crash for gdb.compile/compile.exp

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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Hi,

(gdb) PASS: gdb.compile/compile.exp: set unwindonsignal on
compile code *(volatile int *) 0 = 0;
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7fba426 in _gdb_expr (__regs=0x7ffff7fb8000) at gdb command line:1
1       gdb command line: No such file or directory.
=================================================================
==10462==ERROR: AddressSanitizer: heap-use-after-free on address 0x621000cf7a3d at pc 0x0000004e46b9 bp 0x7ffdeb0f7a40 sp 0x7ffdeb0f71b8
READ of size 10 at 0x621000cf7a3d thread T0
    #0 0x4e46b8 in printf_common(void*, char const*, __va_list_tag*) [clone .isra.6] (/home/jkratoch/redhat/gdb-clean-asan/gdb/gdb+0x4e46b8) 
    #1 0x4f645e in vasprintf (/home/jkratoch/redhat/gdb-clean-asan/gdb/gdb+0x4f645e)
    #2 0xe5cf00 in xstrvprintf common/common-utils.c:120
    #3 0xe74192 in throw_it common/common-exceptions.c:332
    #4 0xe742f6 in throw_verror common/common-exceptions.c:361
    #5 0xddc89e in verror /home/jkratoch/redhat/gdb-clean-asan/gdb/utils.c:541
    #6 0xe734bd in error common/errors.c:43
    #7 0xafa1d6 in call_function_by_hand_dummy /home/jkratoch/redhat/gdb-clean-asan/gdb/infcall.c:1031
    #8 0xe81858 in compile_object_run compile/compile-object-run.c:119
    #9 0xe7733c in eval_compile_command compile/compile.c:577
    #10 0xe7541e in compile_code_command compile/compile.c:153


It is obvious why that happens, dummy_frame_pop() will call compile objfile
cleanup which will free that objfile and NAME then becomes a stale pointer.

Whether the objfile really should be already freed during
call_function_by_hand_dummy() I am not sure.

No regressions on {x86_64,x86_64-m32,i686}-fedora23pre-linux-gnu.


Jan

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gdb/ChangeLog
2015-04-18  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix ASAN crash for gdb.compile/compile.exp.
	* infcall.c (call_function_by_hand_dummy): Use xstrdup for NAME.

diff --git a/gdb/infcall.c b/gdb/infcall.c
index 26c64f6..bbe163f 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -1005,8 +1005,11 @@ When the function is done executing, GDB will silently stop."),
 
   if (stopped_by_random_signal || stop_stack_dummy != STOP_STACK_DUMMY)
     {
-      const char *name = get_function_name (funaddr,
-					    name_buf, sizeof (name_buf));
+      /* Make a copy as NAME may be in an objfile freed by dummy_frame_pop.  */
+      char *name = xstrdup (get_function_name (funaddr,
+					       name_buf, sizeof (name_buf)));
+      make_cleanup (xfree, name);
+
 
       if (stopped_by_random_signal)
 	{