compiler warning cleanup: is_signed_type: compare -1 to 1

Comparing -1 to 0 triggers compiler warnings (gcc -Wtype-limits and
-Wbool-compare) and Coverity warning "Macro compares unsigned to 0".

Comparing -1 to 1 instead takes care of silencing those warnings while
keeping the same behavior.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id42a51759a1c7c669e63588c05f9d4485304c541

diff --git a/include/lttng/bitfield.h b/include/lttng/bitfield.h
index 8ccb108d734b1c1ed09a3e2ab6ad444fa9eb20a1..b0688ff4c68feddda2549b6fb99ef5d80c26d605 100644 (file)
--- a/include/lttng/bitfield.h
+++ b/include/lttng/bitfield.h
@@ -26,30 +26,7 @@
 #error "bitfield.h requires the compiler representation of signed integers to be two's complement."
 #endif
 
-/*
- * _bt_is_signed_type() willingly generates comparison of unsigned
- * expression < 0, which is always false. Silence compiler warnings.
- * GCC versions lower than 4.6.0 do not accept diagnostic pragma inside
- * functions.
- */
-#if defined(__GNUC__) && (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= 40600
-# define _BT_DIAG_PUSH                 _Pragma("GCC diagnostic push")
-# define _BT_DIAG_POP                  _Pragma("GCC diagnostic pop")
-
-# define _BT_DIAG_STRINGIFY_1(x)       #x
-# define _BT_DIAG_STRINGIFY(x)         _BT_DIAG_STRINGIFY_1(x)
-
-# define _BT_DIAG_IGNORE(option)       \
-       _Pragma(_BT_DIAG_STRINGIFY(GCC diagnostic ignored option))
-# define _BT_DIAG_IGNORE_TYPE_LIMITS   _BT_DIAG_IGNORE("-Wtype-limits")
-#else
-# define _BT_DIAG_PUSH
-# define _BT_DIAG_POP
-# define _BT_DIAG_IGNORE
-# define _BT_DIAG_IGNORE_TYPE_LIMITS
-#endif
-
-#define _bt_is_signed_type(type)       ((type) -1 < (type) 0)
+#define _bt_is_signed_type(type)       ((type) -1 < (type) 1)
 
 /*
  * Produce a build-time error if the condition `cond` is non-zero.
@@ -372,7 +349,6 @@ do {                                                                        \
        unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
        unsigned long _start_unit, _end_unit, _this_unit;               \
        unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
-       bool _is_signed_type;                                           \
                                                                        \
        if (!_length) {                                                 \
                *_vptr = 0;                                             \
@@ -384,11 +360,7 @@ do {                                                                       \
        _end_unit = (_end + (_ts - 1)) / _ts;                           \
                                                                        \
        _this_unit = _end_unit - 1;                                     \
-       _BT_DIAG_PUSH                                                   \
-       _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
-       _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
-       _BT_DIAG_POP                                                    \
-       if (_is_signed_type                                             \
+       if (_bt_is_signed_type(__typeof__(_v))                          \
            && (_ptr[_this_unit] & _bt_lshift((type) 1, (_end % _ts ? _end % _ts : _ts) - 1))) \
                _v = ~(__typeof__(_v)) 0;                               \
        else                                                            \
@@ -444,7 +416,6 @@ do {                                                                        \
        unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
        unsigned long _start_unit, _end_unit, _this_unit;               \
        unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
-       bool _is_signed_type;                                           \
                                                                        \
        if (!_length) {                                                 \
                *_vptr = 0;                                             \
@@ -456,11 +427,7 @@ do {                                                                       \
        _end_unit = (_end + (_ts - 1)) / _ts;                           \
                                                                        \
        _this_unit = _start_unit;                                       \
-       _BT_DIAG_PUSH                                                   \
-       _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
-       _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
-       _BT_DIAG_POP                                                    \
-       if (_is_signed_type                                             \
+       if (_bt_is_signed_type(__typeof__(_v))                          \
            && (_ptr[_this_unit] & _bt_lshift((type) 1, _ts - (_start % _ts) - 1))) \
                _v = ~(__typeof__(_v)) 0;                               \
        else                                                            \

diff --git a/include/lttng/events.h b/include/lttng/events.h
index 5d439bcbbcc0a1dc8321819032edb860565c867c..e4d62adb8ad9fc3de9bc4395fd426648d6884a8f 100644 (file)
--- a/include/lttng/events.h
+++ b/include/lttng/events.h
@@ -23,7 +23,7 @@
 #include <lttng/abi-old.h>
 #include <lttng/endian.h>
 
-#define lttng_is_signed_type(type)     (((type)(-1)) < 0)
+#define lttng_is_signed_type(type)     (((type) -1) < (type) 1)
 
 struct lttng_channel;
 struct lttng_session;