compat/posix.h: enable UNUSED warning messages for Clang

Use a dedicated Clang version check for the UNUSED macro. Commit 7c07f36ad2 (git-compat-util.h: GCC deprecated message arg only in GCC 4.5+, 2022-10-05) restricted use of the deprecated attribute's message argument in the UNUSED macro to GCC 4.5 or newer. Clang identifies itself as GNUC 4.2.1 for compatibility, so GIT_GNUC_PREREQ(4, 5) does not detect whether Clang supports the deprecated("...") form. Add GIT_CLANG_PREREQ() macro and use it to enable the UNUSED warning message for Clang 2.9 and newer. Signed-off-by: Dominik Loidolt <dominik.loidolt@univie.ac.at> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Dominik Loidolt committed Jun 13, 2026 at 14:27 UTC 689dc92e501e25ae1ed67410ff51b4359a4f5c3c
1 file changed +13 -1
compat/posix.h
+13 -1
@@ -12,6 +12,9 @@
12 * ... code requiring gcc 2.8 or later ...
13 * #endif
14 *
15 + * Note that Clang and other compilers define __GNUC__ for compatibility; use
16 + * GIT_CLANG_PREREQ() to check for specific Clang versions.
17 + *
18 * This macro of course is not part of POSIX, but we need it for the UNUSED
19 * macro which is used by some of our POSIX compatibility wrappers.
20 */
@@ -22,6 +25,15 @@
25 #define GIT_GNUC_PREREQ(maj, min) 0
26 #endif
27
28 +/* Similar for Clang. */
29 +#if defined(__clang__) && defined(__clang_minor__) && defined(__clang_major__)
30 +# define GIT_CLANG_PREREQ(maj, min) \
31 + ((__clang_major__ > (maj)) || \
32 + (__clang_major__ == (maj) && __clang_minor__ >= (min)))
33 +#else
34 +# define GIT_CLANG_PREREQ(maj, min) 0
35 +#endif
36 +
37 /*
38 * UNUSED marks a function parameter that is always unused. It also
39 * can be used to annotate a function, a variable, or a type that is
@@ -35,7 +47,7 @@
47 * When a parameter may be used or unused, depending on conditional
48 * compilation, consider using MAYBE_UNUSED instead.
49 */
38 -#if GIT_GNUC_PREREQ(4, 5)
50 +#if GIT_GNUC_PREREQ(4, 5) || GIT_CLANG_PREREQ(2, 9)
51 #define UNUSED __attribute__((unused)) \
52 __attribute__((deprecated ("parameter declared as UNUSED")))
53 #elif defined(__GNUC__)