| commit | aa088438784dd76a859eee229ddaec17e0cb0651 | [log] [tgz] |
|---|---|---|
| author | Louis Dionne <ldionne.2@gmail.com> | Wed Aug 21 09:05:55 2024 -0400 |
| committer | GitHub <noreply@github.com> | Wed Aug 21 09:05:55 2024 -0400 |
| tree | c0f688b3840893984d4f28774dd562cbc724288f | |
| parent | 4f14bfeddedcf21e0eaf0ff3ddf7b62938f66df5 [diff] |
[libc++] Avoid -Wzero-as-null-pointer-constant in operator<=> (#79465)
Issue #43670 describes a situation where the following comparison will
issue a warning when -Wzero-as-null-pointer-constant is enabled:
#include <compare>
auto b = (1 <=> 2) < 0;
This code uses operator<(strong_ordering, Unspecified), which is
specified by the Standard to only work with a literal 0. In the library,
this is achieved by constructing Unspecified from a pointer, which works
but has the downside of triggering the warning.
This patch uses an alternative implementation where we require that the
operator is used exactly with an int of value 0 (known at compile-time),
however that value can technically be an expression like `1 - 1`, which
makes us a bit less strict than what's specified in the Standard.
Fixes #43670
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