Re: [PATCH 1/3] Revert "make error()'s constant return value more visible"
- From
Jeff King <peff@peff.net>
- Date
- May 5, 2014, 05:49 UTC
- Message-ID
- <20140505054901.GA19331@sigill.intra.peff.net>
- In-Reply-To
- <1399183975-2346-2-git-send-email-felipe.contreras@gmail.com>
On Sun, May 04, 2014 at 01:12:53AM -0500, Felipe Contreras wrote:
> So it looks like gcc is smarter now, and in trying to fix a few warnings > we generated hundreds more. > > This reverts commit e208f9cc7574f5980faba498d0aa30b4defeb34f.
And now we've gone the other way, and re-enabled the initial warnings. Can we come up with a solution that helps both cases?
I could not find a way to annotate a value as "maybe unused", but we can hide it inside a function, like:
-- >8 -- Subject: inline error() function
The error() function does two things: it prints an error, and it returns "-1" as a convenience to allow:
return error("foo");Commit e208f9c converted this to a macro to make the constant return value more visible to the compiler. However, recent versions of gcc complain when error is used in a void context, as the constant "-1" ends up unused.
Instead, let's convert error() to a static inline, which should accomplish the same thing without the extra warnings (because gcc will not warn about unused return values unless warn_unused_result is specified for the particular function).
Signed-off-by: Jeff King <peff@peff.net> --- git-compat-util.h | 20 ++++++++++++-------- usage.c | 8 +------- 2 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/git-compat-util.h b/git-compat-util.h index f6d3a46..3aef0d3 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -310,7 +310,6 @@ extern NORETURN void usage(const char *err); extern NORETURN void usagef(const char *err, ...) __attribute__((format (printf, 1, 2))); extern NORETURN void die(const char *err, ...) __attribute__((format (printf, 1, 2))); extern NORETURN void die_errno(const char *err, ...) __attribute__((format (printf, 1, 2))); -extern int error(const char *err, ...) __attribute__((format (printf, 1, 2))); extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2))); #ifndef NO_OPENSSL @@ -325,14 +324,19 @@ extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2))) /* * Let callers be aware of the constant return value; this can help - * gcc with -Wuninitialized analysis. We restrict this trick to gcc, though, - * because some compilers may not support variadic macros. Since we're only - * trying to help gcc, anyway, it's OK; other compilers will fall back to - * using the function as usual. + * gcc with -Wuninitialized analysis. */ -#if defined(__GNUC__) && ! defined(__clang__) -#define error(...) (error(__VA_ARGS__), -1) -#endif +__attribute__((format (printf, 1, 0))) +extern void error_impl(const char *err, va_list params); +__attribute__((format (printf, 1, 2))) +static inline int error(const char *err, ...) +{ + va_list params; + va_start(params, err); + error_impl(err, params); + va_end(params); + return -1; +} extern void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params)); extern void set_error_routine(void (*routine)(const char *err, va_list params)); diff --git a/usage.c b/usage.c index ed14645..5456e4b 100644 --- a/usage.c +++ b/usage.c @@ -138,15 +138,9 @@ void NORETURN die_errno(const char *fmt, ...) va_end(params); } -#undef error -int error(const char *err, ...) +void error_impl(const char *err, va_list params) { - va_list params; - - va_start(params, err); error_routine(err, params); - va_end(params); - return -1; } void warning(const char *warn, ...)
-- 2.0.0.rc1.436.g03cb729