[Libunwind-devel] Exception handling routines on x86

[address@hidden]

Hi,

i've tested libunwind's exception handling routines under linux-x86 
(compiled into libunwind via --enable-cxx-exceptions). Initially my test 
program segfaulted, so i've patched the code of libunwind a little bit. 
Two patches are attached.

The first patch addresses a difference between gcc and libunwind: the 
size of exception_class is different - libunwind uses a 32-bit value 
whereas gcc uses and expects a 64-bit value (which equals to 'GNUCC++\0' 
or 'GNUCC++\x01')

The second patch is just a quick'n'dirty fix to get the testing 
executable running correctly. The problem is, that gcc's personality 
function (eh_personailty.cc) uses __builtin_eh_return_data_regno(0) (== 
0) and __builtin_eh_return_data_regno(1) (== 2) to set data registers 
for exception handling with _Unwind_SetGR. It expects EAX and EDX to be 
set, respectively. But libunwind sets EAX and ECX.
So, how should this problem be addressed cleanly? Should the registers 
be renumbered (via UNW_REG_* enums in libunwind-x86.h)? Or should 
_Unwind_SetGR and _Unwind_GetGR be patched to renumber the registers? Or 
do you have any other idea?

My test program can simply be compiled and executed by calling 
test-eh.sh. On my linux machine it fails with gcc's own exception 
handling routines, while libunwind's ones work great with these patches.

Greetings
Stefan

libunwind-exception_class-64bit.patch
Description: Text document

libunwind-setgr-workaround.patch
Description: Text document

test-eh.c
Description: Text Data

test-eh.cxx
Description: Text Data

test-eh.sh
Description: Bourne shell script