Clang-Tidy raises modernize-use-nullptr with spaceship operator

[andrea-cassioli-maersk]

Reopening #53961 as it seems to me the issue is not solved.

I have a simple struct

#include <compare>

struct X {
  double a = 0.0;
  double b = 0.0;
  double c = 0.0;

  X() = default;
  X(const X&) = default;
  explicit X(double x);

  X& operator=(const X& other) = default;
  // NOLINTNEXTLINE(modernize-use-nullptr)
  std::partial_ordering operator<=>(const X&) const = default;
};

if I run clang-tidy I get an error

Resource filename: /opt/homebrew/lib/python3.11/site-packages/clang_tidy/data/bin/clang-tidy 
/Users/***/***.h:23:77: error: use nullptr [modernize-use-nullptr,-warnings-as-errors]
  std::partial_ordering operator<=>(const X&) const = default;
                                                                            ^
                                                                             nullptr

Am I missing anything here?

[llvmbot]

@llvm/issue-subscribers-clang-tidy

[PiotrZSL]

Looks like warning is generated in system header:

include/c++/14.0.0/compare:364:21: warning: use nullptr [modernize-use-nullptr]
  364 |   { return __cmp != 0; }

Do not use --system-header to silent it.
Anyway, duplicate of #63478

[andrea-cassioli-maersk]

hey @PiotrZSL I am not sure I understand your suggestion.

[PiotrZSL]

I mean that those issues are raised in system header, and looks like --warnings-as-errors is causing it to be visible. This issue (check filters) can be already fixed in Clang 17. As for bug in check, that is pending.

Most probably if you disable warnings-as-errors, you wont see this issue.