Re: Problem with catching exceptions on ARM

[Mathias Bauer]

Hi David,

thanks for your answer!

Am 20.02.14 18:33, schrieb David Chisnall:
> On 20 Feb 2014, at 17:27, Mathias Bauer <mathias_bauer@gmx.net>
> wrote:
>
> > The call to _Unwind_Resume_or_Rethrow(e) does not return.
>
> That's not a bad thing.  _Unwind_Resume_or_Rethrow() is only supposed
> to return in error conditions.
>
> > I tested, that a simple @try/@catch works (an exception thrown in a
> > function called from the @try block is caught successfully and the
> > program exits normally). But throwing another exception in the
> > function that caught the exception freezes the program again. It
> > doesn't matter if the second exception is thrown inside the @catch
> > block or outside of it.
>
> Hmm, do you know which exception ABI you're using?  Can you make sure
> that you're compiling with -fobjc-runtime=gnustep-1.7 so that we're
> using the code that emits calls to the functions on entry to and exit
> from catch blocks?  With the old ABI there may be some bugs related
> to exception lifetime (there are also bugs in that the old ABI is
> impossible to implement correctly).

When building libobjc2 and the ExceptionTest.m, I set some CFLAGS before 
letting CMake generate the Makefiles, and CMake seems to evaluate this 
(I know that from an occasion where I accidently had a typo in my 
-fobjc-runtime thingie ;-)).

The resulting command for the compilation is:


clang version 3.5 (trunk nversioned directory)
Target: armv7hl-suse-linux-gnueabi
Thread model: posix
Found candidate GCC installation: 
/usr/lib/gcc/armv7hl-suse-linux-gnueabi/4.8
Selected GCC installation: /usr/lib/gcc/armv7hl-suse-linux-gnueabi/4.8
 "/usr/bin/clang" -cc1 -triple armv7-suse-linux-gnueabi -E 
-disable-free -main-file-name gc_none.c -mrelocation-model pic 
-pic-level 2 -mdisable-fp-elim -fmath-errno -masm-verbose 
-mconstructor-aliases -fuse-init-array -target-cpu cortex-a8 -target-abi 
aapcs-linux -mfloat-abi hard -target-linker-version 12.3 -v -g 
-coverage-file /home/me/libobjc2/build/gc_none.i -resource-dir 
/usr/bin/../lib/clang/3.5 -D GC_DEBUG -D GNUSTEP -D NO_LEGACY -D 
TYPE_DEPENDENT_DISPATCH -D _BSD_SOURCE=1 -D _XOPEN_SOURCE=700 -D 
__BSD_VISIBLE=1 -D __OBJC_RUNTIME_INTERNAL__=1 -D objc_EXPORTS 
-internal-isystem /usr/local/include -internal-isystem 
/usr/bin/../lib/clang/3.5/include -internal-externc-isystem /include 
-internal-externc-isystem /usr/include -O0 
-Wno-deprecated-objc-isa-usage -Wno-objc-root-class -std=gnu99 
-fdebug-compilation-dir /home/me/libobjc2/build -ferror-limit 19 
-fmessage-length 183 -mstackrealign -fno-signed-char 
-fobjc-runtime=gnustep-1.7 -fobjc-dispatch-method=non-legacy 
-fexceptions -fdiagnostics-show-option -fcolor-diagnostics 
-vectorize-slp -o gc_none.i -x c /home/me/libobjc2/gc_none.c
clang -cc1 version 3.5 based upon LLVM 3.5svn default target 
armv7l-unknown-linux-gnueabihf
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/bin/../lib/clang/3.5/include
 /usr/include
End of search list.

Regards,
Mathias