Doxygen only expands macro defined in header file once when referred multiple times

[Jerry-Ma]

With

ENABLE_PREPROCESSING   = YES
MACRO_EXPANSION        = YES

and the following code snippet:

// macro.h
#define meta_enum_class(Type, UnderlyingType, ...)\
    enum class Type : UnderlyingType { __VA_ARGS__}

// use1.h
#include "macro.h"
/** @enum Use1 */
meta_enum_class(Use1, int, a, b, c);

// use2.h
#include "macro.h"
/** @enum Use2 */
meta_enum_class(Use2, int, d, e, f);

Doxygen could not correctly expand both of the macro usage, which results in failure of showing documentation for Use2, or Use1, depending on which file is processed first.

Say, if use1.h is processed first, which doxygen correctly expand the macro there and produces documentation for enum Use1, then at the time it processes use2.h, the macro.h header is skipped so the meta_enum_class macro is not expanded, which is evident upon examining the output with -d preprocess:

Preprocessing /path/to/use2.h...
#include macro.h: already included! skipping...

Any suggestions on how to do this?

[albert-github]

I tried it with version 1.8.15 and didn't see a problem (maybe I looked at the wrong results).
I added to the files:

• a \file statement to be sure the files are included
• some documentation o the Use1 and Use2, now they only have a placeholder.

Which version of doxygen are you using?
Can you please attach a, small, self contained example (source+configuration file in a tar or zip) that allows us to reproduce the problem? Please don't add external links as they might not be persistent. In this case especially the Doxyfile is of importance.

[Jerry-Ma]

I am using Doxygen 1.8.14, installed via home brew on macOS 10.14. Here I am attaching the code that demonstrates the problem.

Please note the

INPUT = @CMAKE_CURRENT_SOURCE_DIR@/src/use1.h \
        @CMAKE_CURRENT_SOURCE_DIR@/src \
        @CMAKE_CURRENT_SOURCE_DIR@/docs

in Doxyfile.in, this causes Use1 in use1.h correctly documented while Use2 in use2.h not. Removing the first item will make both Use1 and Use2 un-documented, because the ordering of files is main.cpp, use1.h, then use2.h, where the macro expansion happens only once during processing main.cpp.

test_doxygen_macro_expansion.tar.gz

[albert-github]

I've just pushed a proposed patch, pull request #6859

[Jerry-Ma]

Thanks for working on that. I am looking forward to seeing it getting to the next release.

Just to get around the issue at the moment, I am using a macro PREDEFINED=DOXYGEN and the following:

#ifdef DOXYGEN
/**
 * @enum Use1
 *  ...docs...
 */
enum class Use1: int {a, b, c};
#else
meta_enum_class(Use1, int, a, b, c);
#endif

[albert-github]

Code has been integrated in master on github (please don't close the issue as this will be done at the moment of a release).

[albert-github]

The mentioned (and currently) merged patch has some negative effects (hanging processes), see #6897.

[albert-github]

Unfortunately patch had to be reverted by #6903 due to #6897.