mark unused parameters in trivial compat functions

When a platform feature isn't available or in use, we sometimes
conditionally compile empty or trivial functions to turn these into
noops. We need to annotate their parameters so that -Wunused-parameters
won't complain about them.

Note that there are many more of these in compat/mingw.h, but we'll
leave them for now, as there's some trickery required to get the UNUSED
macro available there.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/nonblock.c

@@ -41,7 +41,7 @@ int enable_pipe_nonblock(int fd)
 
 #else
 
-int enable_pipe_nonblock(int fd)
+int enable_pipe_nonblock(int fd UNUSED)
 {
 	errno = ENOSYS;
 	return -1;

exec-cmd.c

@@ -252,7 +252,7 @@ static const char *system_prefix(void)
  * This is called during initialization, but No work needs to be done here when
  * runtime prefix is not being used.
  */
-void git_resolve_executable_dir(const char *argv0)
+void git_resolve_executable_dir(const char *argv0 UNUSED)
 {
 }
 

git-compat-util.h

@@ -310,7 +310,9 @@ typedef unsigned long uintptr_t;
 #ifdef PRECOMPOSE_UNICODE
 #include "compat/precompose_utf8.h"
 #else
-static inline const char *precompose_argv_prefix(int argc, const char **argv, const char *prefix)
+static inline const char *precompose_argv_prefix(int argc UNUSED,
+						 const char **argv UNUSED,
+						 const char *prefix)
 {
 	return prefix;
 }
@@ -335,7 +337,9 @@ struct itimerval {
 #endif
 
 #ifdef NO_SETITIMER
-static inline int setitimer(int which, const struct itimerval *value, struct itimerval *newvalue) {
+static inline int setitimer(int which UNUSED,
+			    const struct itimerval *value UNUSED,
+			    struct itimerval *newvalue UNUSED) {
 	return 0; /* pretend success */
 }
 #endif
@@ -420,7 +424,7 @@ int lstat_cache_aware_rmdir(const char *path);
 #endif
 
 #ifndef has_dos_drive_prefix
-static inline int git_has_dos_drive_prefix(const char *path)
+static inline int git_has_dos_drive_prefix(const char *path UNUSED)
 {
 	return 0;
 }
@@ -428,7 +432,7 @@ static inline int git_has_dos_drive_prefix(const char *path)
 #endif
 
 #ifndef skip_dos_drive_prefix
-static inline int git_skip_dos_drive_prefix(char **path)
+static inline int git_skip_dos_drive_prefix(char **path UNUSED)
 {
 	return 0;
 }
@@ -1463,11 +1467,11 @@ int open_nofollow(const char *path, int flags);
 #endif
 
 #ifndef _POSIX_THREAD_SAFE_FUNCTIONS
-static inline void flockfile(FILE *fh)
+static inline void flockfile(FILE *fh UNUSED)
 {
 	; /* nothing */
 }
-static inline void funlockfile(FILE *fh)
+static inline void funlockfile(FILE *fh UNUSED)
 {
 	; /* nothing */
 }