meson: ensure correct version-def.h is used

To build the libgit-version library, Meson first generates `version-def.h` in the build directory. Then it compiles `version.c` into a library. During compilation, Meson tells to include both the build directory and the project root directory. However, when the user previously has compiled Git using Make, they will have a `version-def.h` file in project root directory as well. Because `version-def.h` is included in `version.c` using the #include directive with double quotes, some preprocessors will look for the header file in the same directory as the source file. This will cause compilation of `version.c` ran by Meson to include `version-def.h` previously made by Make, which might be out of date. To explicitly tell the preprocessor which `version-def.h` to use, pass the absolute path of this file as macro GIT_VERSION_H to the preprocessor using option `-D` and have `version.c` `#include GIT_VERSION_H`. To remain working with other build systems than Meson, include "version-def.h" if that macro is not defined. Co-authored-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Toon Claes <toon@iotcl.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Toon Claes committed Jan 14, 2025 at 12:15 UTC 4771501c0a125dd3560391cbd716c63a281e8244
2 files changed +9 -2
meson.build
+3 -1
@@ -1493,7 +1493,9 @@ libgit_version_library = static_library('git-version',
1493 'version.c',
1494 version_def_h,
1495 ],
1496 - c_args: libgit_c_args,
1496 + c_args: libgit_c_args + [
1497 + '-DGIT_VERSION_H="' + version_def_h.full_path() + '"',
1498 + ],
1499 dependencies: libgit_dependencies,
1500 include_directories: libgit_include_directories,
1501 )
version.c
+6 -1
@@ -1,8 +1,13 @@
1 #include "git-compat-util.h"
2 #include "version.h"
3 -#include "version-def.h"
3 #include "strbuf.h"
4
5 +#ifndef GIT_VERSION_H
6 +# include "version-def.h"
7 +#else
8 +# include GIT_VERSION_H
9 +#endif
10 +
11 const char git_version_string[] = GIT_VERSION;
12 const char git_built_from_commit_string[] = GIT_BUILT_FROM_COMMIT;
13