[PATCH v4 0/3] compat/posix.h: enable UNUSED warning messages for Clang

This series enables the intended UNUSED warning message with Clang by adding a dedicated Clang version check. It also cleans up the nearby GIT_GNUC_PREREQ() and UNUSED macros.

Changes since v3:
- split style-only cleanups into their own patch
- fix the UNUSED preprocessor indentation style
- simplify the GIT_GNUC_PREREQ() comparison commit message
- keep the Clang-specific note in the patch that adds GIT_CLANG_PREREQ()

Thanks,
 Dominik

Dominik Loidolt (3):
  compat/posix.h: enable UNUSED warning messages for Clang
  compat/posix.h: clean up GIT_GNUC_PREREQ() and UNUSED
  compat/posix.h: simplify GIT_GNUC_PREREQ() comparison

 compat/posix.h | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

Range-diff against v3:
1:  62f5bce297 ! 1:  9ec87cd815 compat/posix.h: enable UNUSED warning messages for Clang
    @@ Commit message
         Signed-off-by: Dominik Loidolt <dominik.loidolt@univie.ac.at>

      ## compat/posix.h ##
    +@@
    +  *   ... code requiring gcc 2.8 or later ...
    +  *  #endif
    +  *
    ++ * Note that Clang and other compilers define __GNUC__ for compatibility; use
    ++ * GIT_CLANG_PREREQ() to check for specific Clang versions.
    ++ *
    +  * This macro of course is not part of POSIX, but we need it for the UNUSED
    +  * macro which is used by some of our POSIX compatibility wrappers.
    + */
     @@
       #define GIT_GNUC_PREREQ(maj, min) 0
      #endif
2:  a8fe5047a4 ! 2:  1a695af9ca compat/posix.h: simplify GIT_GNUC_PREREQ() comparison
    @@ Metadata
     Author: Dominik Loidolt <dominik.loidolt@univie.ac.at>

      ## Commit message ##
    -    compat/posix.h: simplify GIT_GNUC_PREREQ() comparison
    +    compat/posix.h: clean up GIT_GNUC_PREREQ() and UNUSED

    -    Replace the glibc-style bit-shift version comparison with an explicit
    -    major/minor comparison. This is easier to read and is consistent with
    -    the format already used by GIT_CLANG_PREREQ() and many BSD
    -    <sys/cdefs.h> headers.
    +    Fix the preprocessor indentation of the GIT_GNUC_PREREQ() and UNUSED
    +    macros according to the CodingGuidelines, without changing their
    +    behavior.

    -    This has no runtime impact, as the macro is evaluated at compile time.
    -    It is also more future-proof, as it no longer assumes that GCC version
    -    components stay below 65536.
    +    Adjust the spelling in the GIT_GNUC_PREREQ() comment block.

         Signed-off-by: Dominik Loidolt <dominik.loidolt@univie.ac.at>

      ## compat/posix.h ##
     @@
    - #define _FILE_OFFSET_BITS 64

      /*
    -- * Derived from Linux "Features Test Macro" header
    +  * Derived from Linux "Features Test Macro" header
     - * Convenience macros to test the versions of gcc (or
     - * a compatible compiler).
     + * Convenience macros to test the versions of GCC (or a compatible compiler).
    @@ compat/posix.h
     + *   ... code requiring GCC 2.8 or later ...
       *  #endif
       *
    -+ * Note that Clang and other compilers define __GNUC__ for compatibility; use
    -+ * GIT_CLANG_PREREQ() to check for specific Clang versions.
    -+ *
    +  * Note that Clang and other compilers define __GNUC__ for compatibility; use
    +@@
    +  *
       * This macro of course is not part of POSIX, but we need it for the UNUSED
       * macro which is used by some of our POSIX compatibility wrappers.
     -*/
     + */
      #if defined(__GNUC__) && defined(__GNUC_MINOR__)
      # define GIT_GNUC_PREREQ(maj, min) \
    --	((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
    -+	((__GNUC__ > (maj)) || \
    -+	 (__GNUC__ == (maj) && __GNUC_MINOR__ >= (min)))
    + 	((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
      #else
     - #define GIT_GNUC_PREREQ(maj, min) 0
     +# define GIT_GNUC_PREREQ(maj, min) 0
      #endif

      /* Similar for Clang. */
    +@@
    +  * compilation, consider using MAYBE_UNUSED instead.
    +  */
    + #if GIT_GNUC_PREREQ(4, 5) || GIT_CLANG_PREREQ(2, 9)
    +-#define UNUSED __attribute__((unused)) \
    +-	__attribute__((deprecated ("parameter declared as UNUSED")))
    ++# define UNUSED __attribute__((unused)) \
    ++	__attribute__((deprecated("parameter declared as UNUSED")))
    + #elif defined(__GNUC__)
    +-#define UNUSED __attribute__((unused)) \
    ++# define UNUSED __attribute__((unused)) \
    + 	__attribute__((deprecated))
    + #else
    +-#define UNUSED
    ++# define UNUSED
    + #endif
    +
    + #ifdef __MINGW64__
-:  ---------- > 3:  289b7d9f8e compat/posix.h: simplify GIT_GNUC_PREREQ() comparison

base-commit: a89346e34a937f001e5d397ee62224e3e9852040 -- 2.54.0