bad news re: mingw exceptions

Thu Feb 28 01:39:00 GMT 2002

Adam Megacz wrote:
>>These aren't really c++ exceptions in your example. Because you're
>>compiling CNI, g++ is impersonating Java exceptions.
>>>>Huh, very strange -- if the same code gets emitted, why would the two
>programs behave differently?
>
The two front ends might be generating different code even though they 
are using the same EH runtime.
>At compile time, how does g++ know that test.cc will get linked
>against Java code later on (and hence should emit code for Java
>exceptions, not C++ exceptions)?
>
#pragma gcc java_exceptions
This is declared in some header which is #included from all the CNI 
headers. I think g++ also switches automatically to Java mode when it 
sees a throw or catch of a Java type.
>When I tried to link without -lsupc++ I got unresolved symbols --
>doesn't this mean it's trying to call C++ exceptioning stuff?
>
If its missing __g++_eh_personality or some such symbol, you're using 
C++ EH. If its missing __gcj_eh_personality, you're using Java EH. The 
C++ EH runtime is in libsupc++. The Java EH runtime is in libgcj.
>If the Java and C++ exceptioning mechanisms are totally different, has
>anything changed in the Java ones? 
>
My first suspect would be the builtins patch. This is a random guess. 
Maybe __builtin_setjmp() is broken.
Could you compile your minimal test case with "-O2 -S -fverbose-asm" and 
post the resulting .s file?
regards
Bryce.