https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81870
Bug ID: 81870
Summary: -fsanitize=undefined doesn't pay attention to
__builtin_assume_aligned()
Product: gcc
Version: 7.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: kobalicek.petr at gmail dot com
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
I'm having problem with GCC -fsanitize=undefined and __builtin_assume_aligned()
builtin.
The following code `sanitizer-test.cpp`:
#include <stdint.h>
static __attribute((__noinline__)) uint32_t readu32(const void* p) {
p = __builtin_assume_aligned(p, 1);
return static_cast<const uint32_t*>(p)[0];
}
static __attribute((__noinline__)) void writeu32(void* p, uint32_t x) {
p = __builtin_assume_aligned(p, 1);
static_cast<uint32_t*>(p)[0] = x;
}
int main(int argc, char* argv[]) {
char buf[] = { 0, 1, 2, 3, 4, 5, 6 };
writeu32(buf + 1, 0x44332211);
uint32_t ret = readu32(buf + 1);
return static_cast<int>(ret);
}
Compiled as:
gcc-7 -fsanitize=undefined sanitizer-test.cpp -o sanitizer-test
Outputs the following when executed:
$ ./sanitizer-test
sanitizer-test.cpp:10:32: runtime error: store to misaligned address
0x7ffd643f6ab6 for type 'uint32_t', which requires 4 byte alignment
0x7ffd643f6ab6: note: pointer points here
3f 64 fd 00 01 02 03 04 05 06 00 00 00 00 60 b8 a8 09 b3 55 00 00 b1 f2 ab
be 80 7f 00 00 01 00
^
sanitizer-test.cpp:5:43: runtime error: load of misaligned address
0x7ffd643f6ab6 for type 'const uint32_t', which requires 4 byte alignment
0x7ffd643f6ab6: note: pointer points here
3f 64 fd 00 11 22 33 44 05 06 00 00 00 00 60 b8 a8 09 b3 55 00 00 b1 f2 ab
be 80 7f 00 00 01 00
I think that in this case the sanitizer should not report the runtime error as
the pointer was marked to be aligned to 1 byte.
