[cfe-dev] [C/C++][clang-format] Exempt Specific Function-Like Symbols From The One-Line Rule

[Jacob Faibussowitsch via cfe-dev]

Dear Clang Community,

TL:DR; If at all possible, how can I wrangle clang-format to give me:

1. The following as one line

ierr = FunctionCall();CHKERRQ(ierr);

And not

ierr = FunctionCall();
CHKERRQ(ierr);

2. Function parameters without spaces:

FunctionCall(a,b,c);

And not

FunctionCall(a, b, c);

No holds barred here, modifying clang-format internals/providing patches is not off the table.

————————————

I am a contributor to the Portable Extensible Toolkit for Scientific Computation (PETSc), and have been trying to modernize the tooling workflow within PETSc using clang-tooling. I’ve had great success implementing a linter using the libclang python interface so style enforcement was next on the chopping block.

Like any established code-base we have an opinionated code-style (https://petsc.org/release/developers/style/ <https://petsc.org/release/developers/style/>) which is absolutely powerless against the developer that doesn’t read it. So far we’ve painstakingly enforced it by judicious grep-based checkers (or by hand in code-review :( ). We’d love to use clang-format to automate this but have 2 main sticking points:

1. An error-code checking macro:

#define CHKERRQ(ierr) do {  \
    if (ierr) {             \
      handleError(ierr);    \
    }                       \
  } while (0)

Which is appended to every line, and *must* be on the same line as the call:

ierr = LibraryFunctionCall();CHKERRQ(ierr);

However clang-format will put these on separate lines:

ierr = LibraryFunctionCall();
CHKERRQ(ierr);

2. While this is somewhat more relaxed we don’t use spaces between parameters in function calls:

LibraryFunctionCall(arg1,arg2,arg3);

Which clang-format will change to:

LibraryFunctionCall(arg1, arg2, arg3);


Is there any way around either of these two? We’ve gone through the listed style-options  (https://clang.llvm.org/docs/ClangFormatStyleOptions.html <https://clang.llvm.org/docs/ClangFormatStyleOptions.html>) but there doesn’t seem to be a publicly accessible option for the above. With this in mind, how feasible is it for clang to provide this? How feasible is it to implement these ourselves (perhaps as a clang-tidy-style plugin for clang-format or modifications to clang-format itself)?

Best regards,

Jacob Faibussowitsch
(Jacob Fai - booss - oh - vitch)

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