Ping: https://gcc.gnu.org/pipermail/gcc-patches/2020-September/554893.html
On 9/25/20 12:58 PM, Martin Sebor wrote:
The C and C++ representations of zero-length arrays are different: C uses a null upper bound of the type's domain while C++ uses SIZE_MAX. This makes the middle end logic more complicated (and prone to mistakes) because it has to be prepared for both. A recent change to -Warray-bounds has the middle end create a zero-length array to print in a warning message. I forgot about this gotcha and, as a result, when the warning triggers under these conditions in C++, it causes an ICE in the C++ pretty printer that in turn isn't prepared for the C form of the domain. In my mind, the "right fix" is to make the representation the same between the front ends, but I'm certain that such a change would cause more problems before it solved them. Another solution might be to provide APIs for creating (and querying) arrays and have them call language hooks in cases where the representation might differ. But that would likely be quite intrusive as well. So with that in mind, for the time being, the attached patch just continues to deal with the difference by teaching the C++ pretty printer to also recognize the C form of the zero-length domain. While testing the one line fix I noticed that -Warray-bounds (and therefore, I assume also all other warnings that detect out of bounds accesses to allocated objects) triggers only for the ordinary form of operator new and not for the nothrow overload, for instance. That's because the ordinary form is recognized as a built-in which has the alloc_size attribute attached to it. But because the other forms are neither built-in nor declared in <new> with the same attribute, the warning doesn't trigger. So the patch also adds the attribute to the declarations of these overloads in <new>. In addition, it adds attribute malloc to a couple of overloads of the operator that it's missing from. Tested on x86_64-linux. Martin
