Why am I getting `modernize-use-nullptr` clang tidy error when comparing `std::time_point`?

Question

I don't understand why I am getting this warning when I run my code through clang tidy. I think that the error message is telling me that I am using NULL instead of nullptr, but I am not using NULL anywhere.

https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-nullptr.html:

The check converts the usage of null pointer constants (eg. NULL, 0) to use the new C++11 nullptr keyword.

Here is the code that is causing the error:

#include <chrono>


int
main() {
    using Clock = std::chrono::steady_clock;

    auto const time_point = Clock::now();
    auto const x = time_point < Clock::now();

    return static_cast<int>(x);
}

[ 94%] Building CXX object src/CMakeFiles/app.dir/main.cpp.o
/src/main.cpp:9:28: error: use nullptr [hicpp-use-nullptr,-warnings-as-errors]
        auto const x = time_point < Clock::now();
                                  ^
note: this fix will not be applied because it overlaps with another fix
/src/main.cpp:9:28: error: use nullptr [modernize-use-nullptr,-warnings-as-errors]
note: this fix will not be applied because it overlaps with another fix

1563 warnings generated.
Suppressed 1561 warnings (1561 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
2 warnings treated as errors
make[3]: *** [src/CMakeFiles/app.dir/build.make:83: src/CMakeFiles/app.dir/main.cpp.o] Error 2
make[2]: *** [CMakeFiles/Makefile2:258: src/CMakeFiles/app.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:211: CMakeFiles/run.dir/rule] Error 2
make: *** [Makefile:175: run] Error 2

$ uname -a
Linux desktop 5.6.16-1-MANJARO #1 SMP PREEMPT Wed Jun 3 14:26:28 UTC 2020 x86_64 GNU/Linux

$ clang --version
clang version 10.0.0
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ clang-tidy --version
LLVM (http://llvm.org/):
  LLVM version 10.0.0
  Optimized build.
  Default target: x86_64-pc-linux-gnu
  Host CPU: znver2

$ cat .clang-tidy
---
Checks:          '*,-fuchsia-*,-google-*,-zircon-*,-abseil-*,-modernize-use-trailing-return-type,-llvm-*'
WarningsAsErrors: '*'
HeaderFilterRegex: ''
FormatStyle:     none

In my CMakeLists.txt

find_program(CLANGTIDY clang-tidy)
set(CMAKE_CXX_CLANG_TIDY ${CLANGTIDY} -extra-arg=-Wno-unknown-warning-option)

Please [edit] your question to include the full and complete output (if what you show isn't already). What is this "another fix" mentioned? — Some programmer dude, Aug 02 '20 at 03:14
@Someprogrammerdude Both fixes are included. `hicpp-use-nullptr` and `modernize-use-nullptr` — user1032677, Aug 02 '20 at 03:17
On another note, some operating systems (e.g. POSIX systems like Linux) doesn't allow arbitrary return values from the `main` function. Keep it in the range of an unsigned byte (i.e. `0` to `255`). — Some programmer dude, Aug 02 '20 at 03:19
@Someprogrammerdude, Thanks for the heads up. I didn't know, but I am casting from `bool` so I should be okay. — user1032677, Aug 02 '20 at 03:21
@StephenNewell LLVM and clang 10.0.0, Added it to the question — user1032677, Aug 02 '20 at 03:31
I'm using 10.0.1 on x86_64 linux, and cannot reproduce. I'm including both modernize-* and hipp-* in my checks. What platform are you on? — Stephen Newell, Aug 02 '20 at 03:43
@StephenNewell I tried it without using CMake and got zero errors — user1032677, Aug 02 '20 at 07:09
I encountered a similar problem. I believe it is a manifestation of this `clang-tidy` bug: https://bugs.llvm.org/show_bug.cgi?id=46235 — NicholasM, Apr 09 '21 at 16:38

Why am I getting `modernize-use-nullptr` clang tidy error when comparing `std::time_point`?

0 Answers0