Handle unwinding from SEGV on Windows
Commit Message
PR win32/30255 points out that a call to a NULL function pointer will
leave gdb unable to "bt" on Windows.
I tracked this down to the amd64 windows unwinder. If we treat this
scenario as if it were a leaf function, unwinding works fine.
I'm not completely sure this patch is the best way. I considered
having it check for 'pc==0' -- but then I figured this could affect
any inaccessible PC, not just the special 0 value.
No test case because I can't run dejagnu tests on Windows. I tested
this by hand using the test case in the bug.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30255
---
gdb/amd64-windows-tdep.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
Comments
>>>>> "Tom" == Tom Tromey via Gdb-patches <gdb-patches@sourceware.org> writes:
Tom> PR win32/30255 points out that a call to a NULL function pointer will
Tom> leave gdb unable to "bt" on Windows.
Tom> I tracked this down to the amd64 windows unwinder. If we treat this
Tom> scenario as if it were a leaf function, unwinding works fine.
Tom> I'm not completely sure this patch is the best way. I considered
Tom> having it check for 'pc==0' -- but then I figured this could affect
Tom> any inaccessible PC, not just the special 0 value.
Tom> No test case because I can't run dejagnu tests on Windows. I tested
Tom> this by hand using the test case in the bug.
Tom> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30255
I'm checking this in.
Tom
@@ -1098,13 +1098,14 @@ amd64_windows_frame_cache (frame_info_ptr this_frame, void **this_cache)
cache->sp = extract_unsigned_integer (buf, 8, byte_order);
cache->pc = pc;
+ /* If we can't find the unwind info, keep trying as though this is a
+ leaf function. This situation can happen when PC==0, see
+ https://sourceware.org/bugzilla/show_bug.cgi?id=30255. */
if (amd64_windows_find_unwind_info (gdbarch, pc, &unwind_info,
&cache->image_base,
&cache->start_rva,
- &cache->end_rva))
- return cache;
-
- if (unwind_info == 0)
+ &cache->end_rva)
+ || unwind_info == 0)
{
/* Assume a leaf function. */
cache->prev_sp = cache->sp + 8;