The following code (attaching preprocessed one) crashes with gcc 4.3.3 and gcc
4.4.1 (20090529).
Adding noinline attribute to pop() avoids the crash.
Declaring pop(strict foo *f, void** a) as pop(strict foo *f, int **a) avoids
the crash.
Adding -fno-strict-aliasing avoids the crash.
I'm not sure it does breaks strict aliasing (not the same as casting a "void*"
to a "int*" and dereferencing it). gcc does not prints any warning about strict
aliasing.
Compiled with "gcc-4.4.1 -o out test.c -O3", ran with "./out".
#include
#include
struct foo {
int *a;
void **top;
void *storage[1];
};
void crash(struct foo *f);
int main() {
struct foo f;
int i = 0;
memset(&f, 0, sizeof(f));
f.top = &f.storage[1];
f.a = &i;
crash(&f);
assert(f.top == &f.storage[0]);
assert(f.a == f.storage[0]);
assert(f.a == NULL);
}
void pop(struct foo *f, void **a) {
*a = *(--f->top);
}
__attribute__((noinline))
void crash(struct foo *f) {
while (f->a) {
pop(f, (void**)&f->a);
}
}
--
Summary: strict aliasing and inlining
Product: gcc
Version: 4.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: arnaud dot lb at gmail dot com
GCC build triplet: x86_64-unknown-linux-gnu
GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40305
