[llvm-bugs] [Bug 31738] New: clang-format changes semantics of code on '#define keyword(x)'

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=31738

            Bug ID: 31738
           Summary: clang-format changes semantics of code on '#define
                    keyword(x)'
           Product: clang
           Version: 3.8
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Formatter
          Assignee: unassignedclangbugs at nondot.org
          Reporter: abigail.buccaneer at gmail.com
                CC: djasper at google.com, klimek at google.com,
                    llvm-bugs at lists.llvm.org
    Classification: Unclassified

For certain keywords, '#define keyword(x)' will erroneously insert an extra
space, causing the function-like macro to instead become an object-like macro.
This can change the semantics of the compiled code, which should never happen.

    $ echo '#define if(x)' | clang-format
    #define if (x)

The full list of affected C++ keywords seems to be:

and, and_eq, bitor, case, catch, delete, for, if, new, not_eq, or, or_eq,
return, switch, try, while, xor, xor_eq. Additionally, the MSVC-specific
__except is affected, and __try is not (but I haven't exhaustively tested all
of MSVC's keywords.)

Note that this is not the same as the list of keywords which should be followed
by a space when used normally according to the current style, or the list of
keywords which are recognised by the preprocessor, or the list of keywords
which it's grammatically valid for them to be followed by an open-parenthesis.
In particular, note that bitor is affected, but bitand is not.

    $ clang-format -version
    clang-format version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)

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