[Bug c++/86228] ordered comparison between pointer and zero

[eracpp at eml dot cc]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86228

eracpp <eracpp at eml dot cc> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eracpp at eml dot cc

--- Comment #2 from eracpp <eracpp at eml dot cc> ---
This bug was observed in the following example:

https://gcc.godbolt.org/z/p1VreP

#include <algorithm>
#include <array>

int main()
{
    std::array<int, 3> arr;

    // Mistake: meant to use std::generate.
    std::generate_n(arr.begin(), arr.end(), []{ return 0; });
}

This code successfully compiles (unexpectedly) with GCC due to `size > 0` being
treated as well-formed in the case where the type of second parameter `size` is
deduced to be a pointer type such as `int*`. The contrary behavior is observed
with Clang, as seen in the provided Compiler Explorer link above.

The mistake manifests as an unexpected segmentation fault at runtime, rather
thana compile-time error:

http://coliru.stacked-crooked.com/a/2dc4ae877233c9b2