From 4b5f005b03669c2942969e691fc3a0be47b15c57 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 8 Oct 2013 17:22:42 -0400 Subject: [PATCH 1/1] gcc warning fixes: -Wsign-compare and -Wextra MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When compiling code using the rcu_xchg_pointer() family of functions, with the following define: #define URCU_INLINE_SMALL_FUNCTIONS prior to including urcu headers, when compiling with gcc with -Wsign-compare and -Wextra, gcc warns about: urcu-xchg.c: In function ‘reload’: urcu-xchg.c:19:1: warning: ordered comparison of pointer with integer zero [-Wextra] urcu-xchg.c:19:1: warning: signed and unsigned type in conditional expression [-Wsign-compare] For the "ordered comparison of pointer with integer zero" warning, fix this by comparing (type) -1 against (type) 0 instead of just 0, so if "type" is a pointer type, this pointer type will be applied to the right operand too, thus fixing the warning. For the "signed and unsigned type in conditional expression" warning, we need caa_cast_long_keep_sign() to always evaluate to the same type signedness. In order to do so, when we need to sign-extend the value, cast it to unsigned long after first casting it to long. Reported-by: Stephen Hemminger Signed-off-by: Mathieu Desnoyers --- urcu/compiler.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/urcu/compiler.h b/urcu/compiler.h index c4ade90..19534f0 100644 --- a/urcu/compiler.h +++ b/urcu/compiler.h @@ -86,10 +86,15 @@ #define URCU_FORCE_CAST(type, arg) ((type) (arg)) #endif -#define caa_is_signed_type(type) (((type) (-1)) < 0) +#define caa_is_signed_type(type) ((type) -1 < (type) 0) -#define caa_cast_long_keep_sign(v) \ - (caa_is_signed_type(__typeof__(v)) ? (long) (v) : (unsigned long) (v)) +/* + * Sign-extend to long if needed, and output type is unsigned long. + */ +#define caa_cast_long_keep_sign(v) \ + (caa_is_signed_type(__typeof__(v)) ? \ + (unsigned long) (long) (v) : \ + (unsigned long) (v)) #if defined (__GNUC__) \ && ((__GNUC_MAJOR__ == 4) && (__GNUC_MINOR__ >= 5) \ -- 2.34.1