[Bug c/29970] mixing ({...}) with VLA leads to massive breakage

[gabravier at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=29970

Gabriel Ravier <gabravier at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |gabravier at gmail dot com

--- Comment #19 from Gabriel Ravier <gabravier at gmail dot com> ---
Can also confirm this myself as I've also encountered this ICE in this code:

#include <stdio.h>

#define each(item, array) \
(typeof(*(array)) *foreach_p = (array), *foreach_p2 = foreach_p, (item) = {}; \
foreach_p < &((foreach_p2)[sizeof(array)/sizeof(*array)]); \
++foreach_p)if((__builtin_memcpy(&(item), foreach_p, sizeof((item)))), 0){}else

#define range1(_stop) (({ \
        typeof(_stop) stop = _stop; \
        struct{typeof((stop)) array[stop];}p = {}; \
        if(stop < 0){ \
                for(size_t i = 0; i > stop; --i) \
                        p.array[-i] = i; \
        }else{ \
                for(size_t i = 0; i < stop; ++i) \
                        p.array[i] = i; \
        } \
        p; \
}).array)

int main(){
        char group[][4] = {
                "egg",
                "one",
                "two",
                "moo",
        };
        for each(x, group){
                puts(x);
        }
        return sizeof(range1(6));
}

which I was able to minify to:

void f()
{
  (void)({
    int x = 1;
    struct {
      int array[x];
    } p;
    p;
  });
}

which roughly matches what testcase 2 does.