Wrong formatting of labels in preprocessor lines

[Julien-Elie]

Contrary to previous versions, clang-format 18 reformats:

#    define TXN_START(label, tid) \
    label:                        \
        TXN_START_NORETRY(label, tid)

#    define failure_response           \
    failure:                           \
        simple_response(client, code); \
        break;

as:

#    define TXN_START(label, tid) label : TXN_START_NORETRY(label, tid)

#    define failure_response                     \
        failure : simple_response(client, code); \
        break;

I don't think it is the expected output. Previous versions of clang-format kept it unchanged. It looks like : is now interpreted as a colon in a ternary operation instead of a colon following a label name.

[Julien-Elie]

Incidentally, I'm wondering whether the first example wouldn't be better with a formatting like:

#    define TXN_START(label, tid)     \
    label:                            \
        TXN_START_NORETRY(label, tid)

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: Julien ÉLIE (Julien-Elie)

Contrary to previous versions, clang-format 18 reformats:

#    define TXN_START(label, tid) \
    label:                        \
        TXN_START_NORETRY(label, tid)

#    define failure_response           \
    failure:                           \
        simple_response(client, code); \
        break;

as:

#    define TXN_START(label, tid) label : TXN_START_NORETRY(label, tid)

#    define failure_response                     \
        failure : simple_response(client, code); \
        break;

I don't think it is the expected output. Previous versions of clang-format kept it unchanged. It looks like : is now interpreted as a colon in a ternary operation instead of a colon following a label name.

[owenca]

Previous versions of clang-format kept it unchanged.

Which version(s)? And what's your .clang-format file?

[Julien-Elie]

Hi @owenca, thanks for having taken a look at this bug report. I see that you even already provided fixes. Thanks!

FWIW, my .clang-format is:

Language: Cpp
BasedOnStyle: LLVM
AlignArrayOfStructures: Left
AlignConsecutiveMacros: AcrossEmptyLinesAndComments
AlignEscapedNewlines: Left
AllowShortEnumsOnASingleLine: false
AlwaysBreakAfterReturnType: AllDefinitions
BreakBeforeBinaryOperators: NonAssignment
BreakBeforeBraces: WebKit
ColumnLimit: 79
IncludeCategories:
    - Regex: '^"(config.h|portable/system.h)"'
      Priority: 0
IndentPPDirectives: AfterHash
IndentWidth: 4
IndentWrappedFunctionNames: false
MaxEmptyLinesToKeep: 2
SpaceAfterCStyleCast: true

The previous version I was using is Clang 17.0.6 which had not the issue, nor versions 16, 15, 14, etc. (but I do not remember the exact releases I used for them).

[owenca]

@Julien-Elie I asked which version and what configuration you used because I couldn't make clang-format keep your example unchanged.

$ clang-format -version
clang-format version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
$ cat .clang-format
Language: Cpp
BasedOnStyle: LLVM
AlignArrayOfStructures: Left
AlignConsecutiveMacros: AcrossEmptyLinesAndComments
AlignEscapedNewlines: Left
AllowShortEnumsOnASingleLine: false
AlwaysBreakAfterReturnType: AllDefinitions
BreakBeforeBinaryOperators: NonAssignment
BreakBeforeBraces: WebKit
ColumnLimit: 79
IncludeCategories:
    - Regex: '^"(config.h|portable/system.h)"'
      Priority: 0
IndentPPDirectives: AfterHash
IndentWidth: 4
IndentWrappedFunctionNames: false
MaxEmptyLinesToKeep: 2
SpaceAfterCStyleCast: true
$ cat test.cpp
#    define TXN_START(label, tid) \
    label:                        \
        TXN_START_NORETRY(label, tid)

#    define failure_response           \
    failure:                           \
        simple_response(client, code); \
        break;
$ clang-format test.cpp
#define TXN_START(label, tid) \
    label:                    \
    TXN_START_NORETRY(label, tid)

#define failure_response           \
    failure:                       \
    simple_response(client, code); \
    break;
$ 

However, if I put your example in a #if block, clang-format 17.0.6 will keep it unchanged:

$ cat test2.cpp
#if FOO
#    define TXN_START(label, tid) \
    label:                        \
        TXN_START_NORETRY(label, tid)

#    define failure_response           \
    failure:                           \
        simple_response(client, code); \
        break;
#endif
$ clang-format test2.cpp | diff test2.cpp -
$ 

[owenca]

Incidentally, I'm wondering whether the first example wouldn't be better with a formatting like:

#    define TXN_START(label, tid)     \
    label:                            \
        TXN_START_NORETRY(label, tid)

Maybe, but see the example for ENAS_Left here.

[Julien-Elie]

Oh yes, thanks for your answer.
Maybe an intermediate formatting between ENAS_Left and ENAS_Right could be proposed, or ENAS_Left could take into account the length of the last line. I believe it would improve the overall result, a bit nicer. (But well, that's subjective of course). Thanks anyway for the fix you did about goto labels in macros.