[PATCH 2/2] let clang use the constant-return error() macro

[Jeff King <peff@peff.net>]

Commit e208f9c converted error() into a macro to make its
constant return value more apparent to calling code.  Commit
5ded807 prevents us using this macro with clang, since
clang's -Wunused-value is smart enough to realize that the
constant "-1" is useless in some contexts.

However, since the last commit puts the constant behind an
inline function call, this is enough to prevent the
-Wunused-value warning on both modern gcc and clang. So we
can now re-enable the macro when compiling with clang.

Tested with clang 3.3, 3.4, and 3.5.

Signed-off-by: Jeff King <peff@peff.net>
---
I still get warnings when compiling with clang -O3, due to
-Warray-bounds. It looks like a bug, though. Clang complains that:

  strcmp(argv[1], "git")

oversteps array bounds when the strcmp is expanded into a mess of
builtin magic. So I don't think we are doing anything wrong here.

 cache.h           | 2 +-
 git-compat-util.h | 2 +-
 parse-options.h   | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/cache.h b/cache.h
index e2f12b0..35a3e6b 100644
--- a/cache.h
+++ b/cache.h
@@ -1271,7 +1271,7 @@ extern int check_repository_format_version(const char *var, const char *value, v
 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__)
+#if defined(__GNUC__)
 #define config_error_nonbool(s) (config_error_nonbool(s), const_error())
 #endif
 extern const char *get_log_output_encoding(void);
diff --git a/git-compat-util.h b/git-compat-util.h
index b4c437e..70dc028 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -330,7 +330,7 @@ extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2)))
  * trying to help gcc, anyway, it's OK; other compilers will fall back to
  * using the function as usual.
  */
-#if defined(__GNUC__) && ! defined(__clang__)
+#if defined(__GNUC__)
 static inline int const_error(void)
 {
 	return -1;
diff --git a/parse-options.h b/parse-options.h
index 2f9be96..7940bc7 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -176,7 +176,7 @@ 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__)
+#if defined(__GNUC__)
 #define opterror(o,r,f) (opterror((o),(r),(f)), const_error())
 #endif
 
-- 
2.0.0.rc1.436.g03cb729