[cfe-dev] Initial exception support for the GNU runtime

[David Chisnall]

Hi Everyone,

This patch is a first pass at adding support for exceptions for the  
GNU runtime.  There are a few limitations at present:

- @synchronized() is not yet supported at all.  gcc currently emits  
calls to runtime library functions that don't exist for this directive.

- Only id @catch statements are currently working.  This is enough for  
NS_DURING and friends, but I need to spend more time reading the  
output from gcc -S to work out how it finds the class pointer to make  
arbitrary class type catch statements work.

- I've tested it with a few common cases[1] and the clang test suite  
(which doesn't test exceptions for the GNU runtime, but shows I  
haven't broken anything else), but there are probably a lot of cases  
I've missed.

David

[1] Simple test program:
#import <objc/Object.h>
#include <stdio.h>

void objc_exception_throw(id);
id e;
void foo(void)
{
     e = [Object new];
     @throw e;
}
void nest(void)
{
     @try {
         foo();
     }
     @finally {
         printf("finally 1\n");
     }
}
int main(void)
{
     @try {
         printf("try.\n");
         nest();
         printf("fail.\n");
     }
     @catch(id b) {
         printf("Caught id %d.\n", e == b);
         }
     @finally {
         printf("finally\n");
     }
     return 0;
}


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