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[PATCH] Fix GDB crash in dprintf.exp

I see GDB crashes in dprintf.exp on aarch64-linux testing,

(gdb) PASS: gdb.base/dprintf.exp: agent: break 29
set dprintf-style agent^M
(gdb) PASS: gdb.base/dprintf.exp: agent: set dprintf style to agent
==22475==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x000000494820 sp 0x7fff389b83a0 bp 0x62d000082417 T0)
    #0 0x49481f in remote_add_target_side_commands /home/yao/SourceCode/gnu/gdb/git/gdb/remote.c:9190^M
    #1 0x49e576 in remote_add_target_side_commands /home/yao/SourceCode/gnu/gdb/git/gdb/remote.c:9174^M
    #2 0x49e576 in remote_insert_breakpoint /home/yao/SourceCode/gnu/gdb/git/gdb/remote.c:9240^M
    #3 0x5278b7 in insert_bp_location /home/yao/SourceCode/gnu/gdb/git/gdb/breakpoint.c:2734^M
    #4 0x52ac09 in insert_breakpoint_locations /home/yao/SourceCode/gnu/gdb/git/gdb/breakpoint.c:3159^M
    #5 0x52ac09 in update_global_location_list /home/yao/SourceCode/gnu/gdb/git/gdb/breakpoint.c:12686

the root cause of this problem in this case is about linespec and
symtab which produces additional incorrect location and a NULL is added to
bp_tgt->tcommands.  I posted a patch to fix it
in linespec (the fix causes regression), but GDB still shouldn't add
NULL into bp_tgt->tcommands.  The logic of build_target_command_list
looks odd to me.  If we get something wrong in parse_cmd_to_aexpr (it
returns NULL), we shouldn't continue, instead we should set flag
null_command_or_parse_error.  This is what this patch does.

Regression tested on aarch64-linux.

I have a vague memory that the code here was discussed before, but I
can't find the mail in archive.


2016-01-15  Yao Qi  <>

	* breakpoint.c (build_target_command_list): Don't call continue
	if aexpr is NULL.
 gdb/breakpoint.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 72da4ef..9937b92 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -2552,9 +2552,6 @@ build_target_command_list (struct bp_location *bl)
 	      aexpr = parse_cmd_to_aexpr (bl->address,
 	      loc->cmd_bytecode = aexpr;
-	      if (!aexpr)
-		continue;
 	  /* If we have a NULL bytecode expression, it means something

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