Ping: https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00652.html
This change is independent of either of the two patches below: https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00429.html https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00652.html On 11/18/19 11:22 AM, Martin Sebor wrote:
Ping: https://gcc.gnu.org/ml/gcc-patches/2019-11/msg00652.html On 11/8/19 3:11 PM, Martin Sebor wrote:Unless it's used with _FORTIFY_SOURCE, -Wstringop-overflow doesn't consider out-of-bounds accesses to objects allocated by alloca, malloc, other functions declared with attribute alloc_size, or even VLAs with variable bounds. This was a known limitation of the checks (done just before expansion) relying on the the object size pass when they were introduced in GCC 7. But since its introduction in GCC 7, the warning has evolved beyond some of the limitations of the object size pass. Unlike it, the warning considers non-constant offsets and stores with non-constant sizes. Attached is a simple enhancement that (finally) adds the ability to also detect overflow in allocated objects to the warning. With the patch GCC detects the overflow in code like this: char* f (void) { char s[] = "12345"; char *p = malloc (strlen (s)); strcpy (p, s); // warning here return p; } but not (yet) in something like this: char* g (const char *s) { char *p = malloc (strlen (s)); strcpy (p, s); // no warning (yet) return p; } and quite a few other examples. Doing better requires extending the strlen pass. I'm working on this extension and expect to submit a patch before stage 1 ends. Martin PS I was originally planning to do all the allocation checking in the strlen pass but it occurred to me that by also enhancing the compute_objsize function, all warnings that use it will benefit. Besides -Wstringop-overflow this includes a subset of -Warray-bounds, -Wformat-overflow, and -Wrestrict. It's nice when a small enhancement has such a broad positive effect.
