What is proper LLVM header guard style?

Question

In clang tidy, the check [llvm-header-guard] looks for LLVM style header guards, but I can't find any examples of proper LLVM header guard style, specifically the structure of the name given to the define, the coding standards pages does not mention anything.

Answer 1

Looking at the unit tests:

• https://github.com/llvm-mirror/clang-tools-extra/blob/master/unittests/clang-tidy/LLVMModuleTest.cpp

it seems to accept a few variations on the commonly used patterns. For a file named include/llvm/ADT/foo.h the convention seems to be:

#ifndef LLVM_ADT_FOO_H
#define LLVM_ADT_FOO_H
//...
#endif // LLVM_ADT_FOO_H

Answer 2

Presumably the LLVM codebase adheres to the LLVM coding standards, so one can simply look at a few LLVM header files to get an idea of what the guard looks like. Here are some random LLVM header files I looked at:

https://github.com/llvm-mirror/llvm/blob/master/include/llvm/CodeGen/SelectionDAG.h

https://github.com/llvm-mirror/llvm/blob/master/include/llvm/Support/AlignOf.h

Based on those files, I think the header guard looks like this:

#ifndef LLVM_CODEGEN_SELECTIONDAG_H
#define LLVM_CODEGEN_SELECTIONDAG_H
...
#endif

Answer 3

The proper style for LLVM to detect and be happy with your header is to take the path used to include your header, convert it to uppercase, replace directory separators with underscores, and replace dots in file extensions with underscores.

For instance, if you use #include <dopelib/dopestuff/whatitisyo.h>, your header would be:

#ifndef DOPELIB_DOPESTUFF_WHATITISYO_H
#define DOPELIB_DOPESTUFF_WHATITISYO_H

/** Your code here. **/

#endif

Hope this helps!