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* stdcall lib functions with exception throwing callbacks vs Dwarf2 EH
@ 2004-11-23 22:41 Danny Smith
  2004-11-24  0:47 ` Richard Henderson
  2004-11-24  6:34 ` Aaron W. LaFramboise
  0 siblings, 2 replies; 15+ messages in thread
From: Danny Smith @ 2004-11-23 22:41 UTC (permalink / raw)
  To: gcc; +Cc: Cygwin, mingw-dvlpr

Hi, 
I've been trying to get DW2 EH exception handling working
on windows targets with general success, but have hit a snag.

If a C library function that takes a callback arg is compiled
using stdcall convention, C++ exception thrown by the callback
result in abort.

If the C libarary function uses normal (cdelc) calling convention
than exceptions thrown by callback are handled.

Example:



==============================================
/* callback.c  library functions */
/* compile this with c */

void
caller_c (void (*callback)(void))
{
  callback();
}


void __attribute__((stdcall))
caller_s (void (*callback)(void))
{
  callback();
}

==============================================

/* main.cc */
#include <stdio.h>
extern "C"
{
  typedef void (*foo)(void);
  extern void  caller_c (foo); 
  extern void __attribute__ ((__stdcall__)) caller_s (foo);  
}

void callback (void) 
{
  printf ("Hello from callback\n");
  fflush (stdout);  
  throw 1;
}


int main ()
{
  try {
    printf ("Testing cdecl\n");
    caller_c (callback);
  }
  catch (int) {
    printf ("Caught cdecl\n"); 
  }

  try {
    printf ("\nTesting stdcall\n");
    caller_s (callback);
  }
  catch (int) {
    printf ("Caught stdcall\n");
  }

return 0;
}

==================================================

Compiling with sjlj enabled compiler:

gcc -c -o callback.o callback.c
g++-sjlj -o main-sjlj.exe main.cc callback.o

Both throws are caught.

However, if using DW2 EH enabled compiler

g++-dw2 -omain-dw2.exe main.cc callback.o

I get this:

> Testing cdecl
> Hello from callback
> Caught cdecl

> Testing stdcall
> Hello from callback
>
> abnormal program termination.


This is significant for windows targets, since the
OS win32 api uses stdcall almost exclusively.

Before I pull any more hair out trying, does any one have any hints on
how to use an MD_FALLBACK_FRAME_STATE_FOR to workaround, or is this a
blocker for the use of DW2 EH on windows targets.

Danny

^ permalink raw reply	[flat|nested] 15+ messages in thread
end of thread, other threads:[~2004-11-24 20:43 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2004-11-23 22:41 stdcall lib functions with exception throwing callbacks vs Dwarf2 EH Danny Smith
2004-11-24  0:47 ` Richard Henderson
2004-11-24  7:08   ` Ranjit Mathew
2004-11-24  8:08   ` Danny Smith
2004-11-24  8:26     ` Richard Henderson
2004-11-24  9:41       ` Aaron W. LaFramboise
2004-11-24 17:40         ` Richard Henderson
2004-11-24 18:19           ` Andrew Haley
2004-11-24  8:40   ` Danny Smith
2004-11-24 19:00     ` Richard Henderson
2004-11-24 19:57       ` Andrew Pinski
2004-11-24 20:02         ` Richard Henderson
2004-11-24 21:23       ` Danny Smith
2004-11-24  6:34 ` Aaron W. LaFramboise
2004-11-24  6:58   ` Christopher Faylor

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