llvm dev - Jul 2013 - [LLVMdev] Break in loop expression-3

Hello everyone.

I've noticed the difference in gcc and llvm behaviour with the following
code:

$ cat test.c
#include <stdio.h>
int main()
{
    for(int i = 0;; ({break;}))
                printf("Hello, world\n");
}

$ clang test.c -pedantic && ./a.out
test.c:5:22: warning: use of GNU statement expression extension [-Wgnu]
    for(int i = 0;; ({break;}))
                     ^
1 warning generated.
Hello, world

$ gcc test.c -std=gnu11 -pedantic && ./a.out
test.c: In function 'main':
test.c:5:23: error: break statement not within loop or switch
     for(int i = 0;; ({break;}))
                       ^
test.c:5:21: warning: ISO C forbids braced-groups within expressions
[-Wpedantic]
     for(int i = 0;; ({break;}))

I asked gcc developers about that fact, they answered that gcc is
correct here, because statement expressions don't inherit the
surrounding context. So, it seems to be an llvm bug.

Kind regards,
Markin Alex

On Fri, Jul 12, 2013 at 12:08 PM, Alex Markin <alexanius at gmail.com>
wrote:
> Hello everyone.
>
> I've noticed the difference in gcc and llvm behaviour with the
following code:
>
> $ cat test.c
> #include <stdio.h>
> int main()
> {
>     for(int i = 0;; ({break;}))
>                 printf("Hello, world\n");
> }
>
> $ clang test.c -pedantic && ./a.out
> test.c:5:22: warning: use of GNU statement expression extension [-Wgnu]
>     for(int i = 0;; ({break;}))
>                      ^
> 1 warning generated.
> Hello, world
>
> $ gcc test.c -std=gnu11 -pedantic && ./a.out
> test.c: In function 'main':
> test.c:5:23: error: break statement not within loop or switch
>      for(int i = 0;; ({break;}))
>                        ^
> test.c:5:21: warning: ISO C forbids braced-groups within expressions
> [-Wpedantic]
>      for(int i = 0;; ({break;}))
>
> I asked gcc developers about that fact, they answered that gcc is
> correct here, because statement expressions don't inherit the
> surrounding context.
That's simply wrong.
> So, it seems to be an llvm bug.
This is essentially the same as http://llvm.org/bugs/show_bug.cgi?id=8880 .

-Eli