Jack Howarth a écrit :
On Thu, Feb 04, 2010 at 08:12:10PM +0100, jacob navia wrote:
Hi
I have developed a JIT for linux 64 bits. It generates exception
handling information
according to DWARF under linux and it works with gcc 4.2.1.
I have recompiled the same code under the Macintosh and something has
changed,
apparently, because now any throw that passes through my code crashes.
Are there any differences bertween the exception info format between the
macintosh and linux?
The st...@the moment of the throw looks like this:
CPP code compiled with gcc 4.2.1 calls
JIT code generated on the fly by my JIT compiler that calls
CPP code compiled with gcc 4.2.1 that throws. The catch
is in the CPP code
The throw must go through the JIT code, so it needs the DWARF frame
descriptions
that I generate. Apparently there is a difference.
Thanks in advance for any information.
jacob
Jacob,
Are you compiling on darwin10 and using the Apple or FSF
gcc compilers? If you are using Apple's, this question should
be on the darwin-devel mailing list instead.
I did that. I was compiling with Apple's gcc.
Now, I downloaded the source code of gcc 4.2.1 and compiled that in my Mac.
The build crashed in the java section by the way, there was a script that
supposed the object files in a .libs directory but the objects were in the
same directory as the source code. This happened several times, so at the
end I stopped since I am not interested in Java.
I installed gcc, everything went OK, and I recompiled the source code
with the new gcc.
Then, in the new executable, the normal throws that have been working
under the Apple's gcc do not work anymore and any throw (not only those
that go through the JIT) fail.
I do not understand what is going on.
I would mention
though that darwin10 is problematic in that the libgcc and its
unwinder calls are now subsumed into libSystem. This means that
regardless of how you try to link in libgcc, the new code in
libSystem will always be used. For darwin10, Apple decided to
default their linker over to compact unwind which causes problems
with some of the java testcases on gcc 4.4.x. This is fixed for
FSF gcc 4.5 by forcing the compiler to always link with the
-no_compact_unwind option.
If you use that option I get
ld: symbol dyld_stub_binding_helper not defined (usually in
crt1.o/dylib1.o/bundle1.o)
and Apple's linker refuses to go on.
Another complexity is that Apple
decided to silently abort some of the libgcc calls (now in
libSystem) that require access to FDEs like _Unwind_FindEnclosingFunction().
The reasoning was that the default behavior (compact unwind info) doesn't
use FDEs.
This is fixed for gcc 4.5 by
http://gcc.gnu.org/ml/gcc-patches/2009-12/msg00998.html.
If you are using any other unwinder call that is now silently
aborting, let me know as it may be another that we need to re-export
under a different name from libgcc_ext. Alternatively, you may
be able to work around this issue by using -mmacosx-version-min=10.5
under darwin10.
Jack
OK, now, what would be the procedure for getting to avoid Apple's
modifications to the
exception handling stuff?
Pleeeeeeeze :-)
P.S. If this discussion does not belong in this list please send me just
an email.
Thanks for your answers.
jacob
