[Bug c++/113565] New: __builtin_clz(0) is undefined behavior, but not detected in constant expressions

[janschultke at googlemail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113565

            Bug ID: 113565
           Summary: __builtin_clz(0) is undefined behavior, but not
                    detected in constant expressions
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janschultke at googlemail dot com
  Target Milestone: ---

Code to reproduce
=================

static_assert(__builtin_clz(0));


Actual output (https://godbolt.org/z/v6v5nGxv8)
===============================================

None.


Expected output (Clang)
=======================

<source>:1:15: error: static assertion expression is not an integral constant
expression
    1 | static_assert(__builtin_clz(0));
      |               ^~~~~~~~~~~~~~~~