http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51990
--- Comment #3 from vries at gcc dot gnu.org 2012-01-25 10:15:53 UTC --- (In reply to comment #2) > This extension is not even documented, see PR 37428 for more info. > There are at least these 3 examples in the testsuite that use this extension: gcc.c-torture/compile/20030224-1.c gcc.c-torture/execute/20020412-1.c gcc.dg/lto/20090706-1_0.c These 3 tests fail (in unmodified form) with my patch for PR51879 (see PR51879 comment 7) on this ICE. > I want to say this example is invalid as the function foo does not have enough > info about the size of struct s. If the example is indeed valid, it would be nice if the compiler at least warned about that. Either way, the last 2 tests listed above use (int, ...) as prototype. IIUC, using that prototype would remove your concern about invalidity. Using that prototype instead, I get the same ICE: ... int zzz (char *s1, char *s2, int len, int *q) { int z = 5; unsigned int i, b; struct s { char a[z]; }; struct s x; extern int foo (int, ...) __attribute__((pure)); for (i = 0; i < len; i++) s1[i] = s2[i]; b = z & 0x3; len += (b == 0 ? 0 : 1) + z; *q = len; return foo (z, x, x); } ... I suppose another way to achieve the same is to use a nested function: ... __attribute__((pure,noinline)) int foo (struct s s1, struct s s2) { return 0; } ...