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commit 62261490a36c6911c5eb61be7cddcfb1bd19ba18
Author: Pedro Alves <palves@redhat.com>
Date: Thu Jan 16 17:43:26 2014 +0000
Fix gdb.trace/mi-traceframe-changed.exp on s390.
The test fails on s390 with:
-trace-find frame-number 0^M
&"PC not available\n"^M
^done,found="1",tracepoint="1",traceframe="0",frame={level="-1",addr="<unavailable>",func="??",args=[]}^M
(gdb) ^M
FAIL: gdb.trace/mi-traceframe-changed.exp: tfile: -trace-find frame-number 0
tfile knows to infer the PC from the tracepoint's address if the PC
wasn't collected (tfile_fetch_registers) but, that only works on
targets whose PC register is a raw register, and on s390, the PC
register is a pseudo register.
But even if GDB doesn't know how to infer the value of PC, saying the
current frame is level -1 is a bug:
^done,found="1",tracepoint="1",traceframe="0",frame={level="-1",addr="<unavailable>",func="??",args=[]}^M
^^^^^^^^^
'-1' is the level of the sentinel frame, which should never be visible.
This is caused by the s390's heuristic unwinder accepting the frame
(the fallback heuristic unwinders _always_ accept the frame), but then
the unwind->this_id method throws that "PC not available\n" error.
IOW, the s390's heuristic unwinder was never adjusted to handle
unavailable register values gracefully, which can happen with e.g., a
trimmed core file too.
This is just the minimal necessary for
<unavailable> frames, which at least gets us:
(gdb) tfind
Found trace frame 0, tracepoint 1
#0 <unavailable> in ?? ()
That is, frame #0 instead of -1.
We could get better info out of "info frame" (this patch makes us show
"outermost"), but this change would still be necessary.
gdb/
2014-01-16 Pedro Alves <palves@redhat.com>
* s390-linux-tdep.c (s390_frame_unwind_cache): Swallow
NOT_AVAILABLE_ERROR errors while parsing the prologue or reading
the backchain.
Index: gdb-7.6.1/gdb/s390-tdep.c
===================================================================
--- gdb-7.6.1.orig/gdb/s390-tdep.c
+++ gdb-7.6.1/gdb/s390-tdep.c
@@ -1995,7 +1995,9 @@ static struct s390_unwind_cache *
s390_frame_unwind_cache (struct frame_info *this_frame,
void **this_prologue_cache)
{
+ volatile struct gdb_exception ex;
struct s390_unwind_cache *info;
+
if (*this_prologue_cache)
return *this_prologue_cache;
@@ -2006,10 +2008,15 @@ s390_frame_unwind_cache (struct frame_in
info->frame_base = -1;
info->local_base = -1;
- /* Try to use prologue analysis to fill the unwind cache.
- If this fails, fall back to reading the stack backchain. */
- if (!s390_prologue_frame_unwind_cache (this_frame, info))
- s390_backchain_frame_unwind_cache (this_frame, info);
+ TRY_CATCH (ex, RETURN_MASK_ERROR)
+ {
+ /* Try to use prologue analysis to fill the unwind cache.
+ If this fails, fall back to reading the stack backchain. */
+ if (!s390_prologue_frame_unwind_cache (this_frame, info))
+ s390_backchain_frame_unwind_cache (this_frame, info);
+ }
+ if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+ throw_exception (ex);
return info;
}