[pulseaudio-discuss] [PATCH 2/2] core: Fix GCC 6 compiler warning regarding left shift of negative value

[Peter Meerwald]

In file included from pulse/timeval.c:32:0:
pulse/timeval.c: In function 'pa_timeval_add':
./pulsecore/macro.h:303:28: warning: left shift of negative value [-Wshift-negative-value]
              ? ~(~(type) 0 << (8*sizeof(type)-1))

reported by Ubuntu gcc-6

gcc-6 adds -Wshift-negative-value (enabled by -Wextra) which warns
about left shifting a negative value. Such shifts are undefined
because they depend on the representation of negative values.

also works with -Wshift-overflow=2

Signed-off-by: Peter Meerwald <pmeerw at pmeerw.net>
---
 src/pulsecore/macro.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/pulsecore/macro.h b/src/pulsecore/macro.h
index 1716f81..1e15f4f 100644
--- a/src/pulsecore/macro.h
+++ b/src/pulsecore/macro.h
@@ -298,14 +298,16 @@ static inline size_t PA_PAGE_ALIGN(size_t l) {
 
 #define PA_INT_TYPE_SIGNED(type) (!!((type) 0 > (type) -1))
 
+#define PA_INT_TYPE_HALF(type) ((type) 1 << (sizeof(type)*8 - 2))
+
 #define PA_INT_TYPE_MAX(type)                                          \
     ((type) (PA_INT_TYPE_SIGNED(type)                                  \
-             ? ~(~(type) 0 << (8*sizeof(type)-1))                      \
+             ? (PA_INT_TYPE_HALF(type) - 1 + PA_INT_TYPE_HALF(type))   \
              : (type) -1))
 
 #define PA_INT_TYPE_MIN(type)                                          \
     ((type) (PA_INT_TYPE_SIGNED(type)                                  \
-             ? (~(type) 0 << (8*sizeof(type)-1))                       \
+             ? (-1 - PA_INT_TYPE_MAX(type))                            \
              : (type) 0))
 
 /* We include this at the very last place */
-- 
2.7.0