On Thu, May 29, 2025 at 09:17:14AM -0700, Junio C Hamano wrote:

Carlo Marcelo Arenas Belón [off-list ref] writes:

quoted

Since f93b2a0424 (reftable/basics: introduce `REFTABLE_UNUSED`
annotation, 2025-02-18), the reftable library was migrated to
use an internal version of `UNUSED`, which unconditionally sets
a GNU __attribute__ to avoid warnings function parameters that
are not being used.

Make the definition conditional to prevent breaking the build
with non GNU compilers.

Quite a reasonable reasoning.

quoted

Reported-by: "Randall S. Becker" <redacted>
Signed-off-by: Carlo Marcelo Arenas Belón <redacted>
---
 reftable/basics.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/reftable/basics.h b/reftable/basics.h
index d8888c1262..7d22f96261 100644
--- a/reftable/basics.h
+++ b/reftable/basics.h

@@ -16,7 +16,11 @@
 #include "system.h"
 #include "reftable-basics.h"
 
+#ifdef __GNUC__
 #define REFTABLE_UNUSED __attribute__((__unused__))
+#else
+#define REFTABLE_UNUSED
+#endif

Corresponding definition we use in the main part of the project
defined in compat/posix.h looks like this:

        #if GIT_GNUC_PREREQ(4, 5)
        #define UNUSED __attribute__((unused)) \
                __attribute__((deprecated ("parameter declared as UNUSED")))
        #elif defined(__GNUC__)
        #define UNUSED __attribute__((unused)) \
                __attribute__((deprecated))
        #else
        #define UNUSED
        #endif

GCC 4.5 or older may no longer be relevant, in which case yours may
be good enough.

What I don't understand though: we have a `MAYBE_UNUSED` macro that has
the exact same definition in "git-compat-util.h". Why does the macro
cause issues in the reftable library, but not over there?

Patrick