inline constant return from error() function

Commit e208f9c introduced a macro to turn error() calls
into:

(error(), -1)

to make the constant return value more visible to the
calling code (and thus let the compiler make better
decisions about the code).

This works well for code like:

return error(...);

but the "-1" is superfluous in code that just calls error()
without caring about the return value. In older versions of
gcc, that was fine, but gcc 4.9 complains with -Wunused-value.

We can work around this by encapsulating the constant return
value in a static inline function, as gcc specifically
avoids complaining about unused function returns unless the
function has been specifically marked with the
warn_unused_result attribute.

We also use the same trick for config_error_nonbool and
opterror, which learned the same error technique in a469a10.

Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/cache.h b/cache.h
index ebe9a405d811b2cc6b64109db135bb8ca4096e9e..001b63f5cd0f31658686c566e1261c347ad36fa0 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -1184,7 +1184,7 @@ extern int git_env_bool(const char *, int);
 extern int git_config_system(void);
 extern int config_error_nonbool(const char *);
 #if defined(__GNUC__) && ! defined(__clang__)
-#define config_error_nonbool(s) (config_error_nonbool(s), -1)
+#define config_error_nonbool(s) (config_error_nonbool(s), const_error())
 #endif
 extern const char *get_log_output_encoding(void);
 extern const char *get_commit_output_encoding(void);

diff --git a/git-compat-util.h b/git-compat-util.h
index d493a8c67ac1a91c40dfff0023c6ecf14155c09a..90b988a5c191ed8810ea73ebfe30426bdeb083ba 100644 (file)
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -343,7 +343,11 @@ extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2)))
  * using the function as usual.
  */
 #if defined(__GNUC__) && ! defined(__clang__)
-#define error(...) (error(__VA_ARGS__), -1)
+static inline int const_error(void)
+{
+       return -1;
+}
+#define error(...) (error(__VA_ARGS__), const_error())
 #endif
 
 extern void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params));

diff --git a/parse-options.h b/parse-options.h
index d670cb9669f213951b9b2cac332c7869be6ca2ee..1ef8da1f3e2b20bccfc856b03daab801f224579c 100644 (file)
--- a/parse-options.h
+++ b/parse-options.h
@@ -180,7 +180,7 @@ extern NORETURN void usage_msg_opt(const char *msg,
 extern int optbug(const struct option *opt, const char *reason);
 extern int opterror(const struct option *opt, const char *reason, int flags);
 #if defined(__GNUC__) && ! defined(__clang__)
-#define opterror(o,r,f) (opterror((o),(r),(f)), -1)
+#define opterror(o,r,f) (opterror((o),(r),(f)), const_error())
 #endif
 
 /*----- incremental advanced APIs -----*/