gcc4: throwing exception from signal handler

[Don Ward]

I would like to be able to catch certain signals (SIGSEGV and SIGSYS) and throw a C++ exception (to be caught in a try/catch construct). As a simple example:

#include <stdio.h>
#include <string.h>
#include <stdexcept>
#include <signal.h>
void throw_signal( int signum )
{

 throw std::runtime_error ("throw_signal");
}
int main() {
 struct sigaction new_action, d_old_action;
 memset (&new_action, 0, sizeof (new_action));
 new_action.sa_handler = throw_signal;
 sigemptyset (&new_action.sa_mask);
 new_action.sa_flags = 0;
 if (sigaction (SIGSEGV, &new_action, &d_old_action) < 0){
   perror ("sigaction (install new)");
   throw std::runtime_error ("sigaction");
 }
 try {
   int j = *((int *)NULL);
 }
 catch (...){
   printf("caught exception\n");
 }
}

g++ 3.3.4 gives the result I expect:

$ sh /usr/bin/set-gcc-default-3.sh
$ gcc --version
gcc (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)
Copyright (C) 2004 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ g++ -fnon-call-exceptions throw_segv.cc
$ ./a.exe
caught exception

but g++ 4.3.4 aborts after the exception is thrown and before it is caught:

$ sh /usr/bin/set-gcc-default-4.sh
$ gcc --version
gcc (GCC) 4.3.4 20090804 (release) 1
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ g++ -fnon-call-exceptions throw_segv.cc
$ ./a.exe
terminate called after throwing an instance of 'std::runtime_error'
 what():  throw_signal
Aborted (core dumped)



Thanks,

-- Don W.

// fprintf(stderr,"throw_signal: before throw; signum=%d\n",signum);fflush(stderr); Am I misunderstanding how this should work or doing something wrong? Or is this a problem with Cygwin or gcc?

cygcheck.out
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throw_segv.cc
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