clang-tidy misc-include-cleaner bug

[thomedes-taxitronic]

Only happens when the macro is named 'I'. If it's renamed to 'H' it's fine.

$ clang-tidy -checks='-*,misc-include-cleaner' /tmp/prova.c --
1 warning generated.
/tmp/prova.c:3:16: warning: no header providing "I" is directly included [misc-include-cleaner]
    1 | #define I 42
    2 | 
    3 | void f(void) { I; }
      |                ^

$ clang-tidy --version
Debian LLVM version 20.1.8
  Optimized build.

prova.c

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Toni Homedes i Saun (thomedes-taxitronic)

Details

Only happens when the macro is named 'I'. If it's renamed to 'H' it's fine.

$ clang-tidy -checks='-*,misc-include-cleaner' /tmp/prova.c --
1 warning generated.
/tmp/prova.c:3:16: warning: no header providing "I" is directly included [misc-include-cleaner]
    1 | #define I 42
    2 | 
    3 | void f(void) { I; }
      |                ^

$ clang-tidy --version
Debian LLVM version 20.1.8
  Optimized build.

prova.c

[llvmbot]

@llvm/issue-subscribers-clang-include-cleaner

Author: Toni Homedes i Saun (thomedes-taxitronic)

Details

Only happens when the macro is named 'I'. If it's renamed to 'H' it's fine.

$ clang-tidy -checks='-*,misc-include-cleaner' /tmp/prova.c --
1 warning generated.
/tmp/prova.c:3:16: warning: no header providing "I" is directly included [misc-include-cleaner]
    1 | #define I 42
    2 | 
    3 | void f(void) { I; }
      |                ^

$ clang-tidy --version
Debian LLVM version 20.1.8
  Optimized build.

prova.c

[chrchr-github]

This might be related:

#include <complex.h>

_Complex float f() { return I; }

<source>:1:1: warning: included header complex.h is not used directly [misc-include-cleaner]
    1 | #include <complex.h>
      | ^~~~~~~~~~~~~~~~~~~~
    2 | 
1 warning generated.

https://godbolt.org/z/v8M3doxEf

Note that the original example is C and only reproduces as C. The code above is C++.

[zeyi2]

Thanks for reporting the issue!

I think clang/lib/Tooling/Inclusions/Stdlib/CSymbolMap.inc maps I to <complex.h>. I'll investigate further when I have time.