Ping: https://gcc.gnu.org/pipermail/gcc-patches/2020-July/549686.html
(Jeff, I forgot to mention this patch when we spoke earlier today.) On 7/8/20 6:01 PM, Martin Sebor wrote:
GCC has gotten better at detecting conflicts between various attributes but it still doesn't do a perfect job of detecting similar problems due to mismatches between contradictory arguments to the same attribute. For example, __attribute ((alloc_size (1))) void* allocate (size_t, size_t); followed by __attribute ((alloc_size (2))) void* allocate (size_t, size_t); is accepted with the former overriding the latter in calls to the function. Similar problem exists with a few other attributes that take arguments. The attached change adds a new utility function that checks for such mismatches and issues warnings. It also adds calls to it to detect the problem in attributes alloc_align, alloc_size, and section. This isn't meant to be a comprehensive fix but rather a starting point for one. Tested on x86_64-linux. Martin PS I ran into this again while debugging some unrelated changes and wondering about the behavior in similar situations to mine. Since the behavior seemed clearly suboptimal I figured I might as well fix it. PPS The improved checking triggers warnings in a few calls to __builtin_has_attribute due to apparent conflicts. I've xfailed those in the test since it's a known issue with some existing attributes that should be fixed at some point. Valid uses of the built-in shouldn't trigger diagnostics except for completely nonsensical arguments. Unfortunately, the line between valid and completely nonsensical is a blurry one (GCC either issues errors, or -Wattributes, or silently ignores some cases altogether, such as those that are the subject of this patch) and there is no internal mechanism to control the response.
