Clang-Tidy not excluding system headers

[FaiqueAli]

Hi everyone,
I am trying to analyze a project on Ubuntu using clang-tidy version

Ubuntu LLVM version 14.0.0

  Optimized build.
  Default target: x86_64-pc-linux-gnu
  Host CPU: tigerlake

but I am getting a lot of errors from system header files.
I have created a compile_command.json file and also added the path of system header files in compile_command.json file to ignore system headers.
Similarly, I used the //NOLINT option and still got errors from the system header files.

I executed clang-tidy -checks='cppcoreguidelines' -header-filter=.* -p path/compile_commands.json src/*.cpp
here is the output of the command clang-tidy-output.txt

looking for help to resolve the issue.
Thanks :)

[llvmbot]

@llvm/issue-subscribers-clang-tidy

[EugeneZelenko]

Could you please try 17 Release Candidate or main branch?

[PiotrZSL]

You got compiler errors:

error: too many errors emitted, stopping now [clang-diagnostic-error]
error: unsupported option '-V gcc_ntoaarch64le' [clang-diagnostic-error]
/home/sayedf/qnx710/target/qnx7/usr/include/signal.h:79:2: error: unknown type name 'sigset_t' [clang-diagnostic-error]

Errors will be always displayed regardless of system headers settings.
System headers filter work only for warnings.

Clang-tidy require input file to actually compile to perform analise. AST tree need to be constructor and that cannot be done if some types are missing.

Fix compile errors, verify using clang itself.
Verify if system headers are included with -isystem.

Nothing to fix here on Clang-tidy side.

[FaiqueAli]

Hi,
Thanks for replying and sorry for the late rep.

You got compiler errors:

error: too many errors emitted, stopping now [clang-diagnostic-error]
error: unsupported option '-V gcc_ntoaarch64le' [clang-diagnostic-error]
/home/sayedf/qnx710/target/qnx7/usr/include/signal.h:79:2: error: unknown type name 'sigset_t' [clang-diagnostic-error]

Errors will be always displayed regardless of system headers settings. System headers filter work only for warnings.

Clang-tidy require input file to actually compile to perform analise. AST tree need to be constructor and that cannot be done if some types are missing.

Fix compile errors, verify using clang itself. Verify if system headers are included with -isystem.

Nothing to fix here on Clang-tidy side.

So the code is being compiled successfully (make -j8 all ) without clang-tidy, please have a look at this attachment.

@PiotrZSL I did not understand why the status of the issue has changed to CLOSE ?

Could you please try 17 Release Candidate or main branch?

@EugeneZelenko
I have installed clang-tidy-17 in my Ubuntu using sudo apt install clang-tidy-17 and still getting the same header diagnostic issue with the command below

clang-tidy-17 -checks='cppcoreguidelines' -header-filter=.* -p path/compile_commands.json src/*.cpp

All the errors are being pointed out toward system headers as shown below,

/home/sayedf/qnx710/target/qnx7/usr/include/sys/siginfo.h:568:6: error: unknown type name 'clock_t' [clang-diagnostic-error]
  568 |                                         clock_t                 __utime;

please have a look at the output of clang-tidy-17

[carlosgalvezp]

I see you are analyzing code that depends on QNX headers. It's likely clang-tidy (or clang for that matter) have issues with those, since they are platform-specific. Can you post the compile_commands.json file?

[FaiqueAli]

Yes, I am using QNX compiler and here is the compile_command.json file,
Please have a look :)

[carlosgalvezp]

Thanks for sharing!

• First, I see this:

      "-I/home/sayedf/qnx710/target/qnx7/usr/include",

You should include via -isystem instead of -I to ensure it's treated as a system header.

• You are probably missing more -isystem lines to QNX include folders. Clang/clang-tidy complains it can't find clock_t, because it's probably defined only in a QNX-specific header. Since you haven't added an include path to it, clang-tidy picks the x86 system headers, which don't define that type. To get the complete list of include paths you need, run:

qcc -E -v -

And you'll get the list here:

#include <...> search starts here:
...

Alternatively you might be able to simply pass --sysroot /home/sayedf/qnx710/target/qnx7 and skip -isystem lines but I'm not sure if you'll get other complications.

[FaiqueAli]

Thank you @carlosgalvezp for the information.

Do you mean -I/home/sayedf/qnx710/target/qnx7/usr/include defined in the compile_command.json file?

Since this file is being generated by Bear it would be difficult to manually correct the number of lines in the file each time, but for the rectification, I will now try to replace -I with -isystem.
should this correction only go to the system header files path in compile_command.json file or I should replace all the occurrences of -I with -isystem?

Do you also mean to try to replace -isystem with --sysroot /home/sayedf/qnx710/target/qnx7 in the compile_command.json file or pass this as a clang-tidy command argument?

thanks and looking forward to the clarification :)

[carlosgalvezp]

Do you mean -I/home/sayedf/qnx710/target/qnx7/usr/include defined in the compile_command.json file?

Yes

should replace all the occurrences of -I with -isystem

No, that will essentially make clang-tidy ignore all warnings :) It should be added only to system libraries and 3rd-party libraries, not to your own libraries.

I meant try to replace:

-I/home/sayedf/qnx710/target/qnx7/usr/include

With:

--sysroot /home/sayedf/qnx710/target/qnx7

[FaiqueAli]

Great

So I will now get a list of header files only using qcc -E -v - and replace it with --sysroot and let see the outcome :)