diff options
authorSzabolcs Nagy <>2012-12-19 10:57:54 +0100
committerSzabolcs Nagy <>2012-12-19 10:57:54 +0100
commit3c4214db727ed6300b34be28a5428b7abd6598df (patch)
parente9e2b66e687bc0b4d07305a2b288ed8ff4ae5b4b (diff)
math: more correct tgmath.h type cast logic
__IS_FP is a portable integer constant expression now (uses that unsigned long long is larger than float) the result casting logic should work now on all compilers supporting typeof
1 files changed, 17 insertions, 32 deletions
diff --git a/include/tgmath.h b/include/tgmath.h
index 25ad0071..e41ccac9 100644
--- a/include/tgmath.h
+++ b/include/tgmath.h
@@ -13,7 +13,7 @@ sizeof(double) == sizeof(long double)
#include <math.h>
#include <complex.h>
-#define __IS_FP(x) !!((1?1:(x))/2)
+#define __IS_FP(x) (sizeof((x)+1ULL) == sizeof((x)+1.0f))
#define __IS_CX(x) (__IS_FP(x) && sizeof(x) == sizeof((x)+I))
#define __IS_REAL(x) (__IS_FP(x) && 2*sizeof(x) == sizeof((x)+I))
@@ -28,57 +28,42 @@ sizeof(double) == sizeof(long double)
#ifdef __GNUC__
-the conditional expression (that selects the right function
-for evaluation) should be casted to the return type of the
-selected function (otherwise the result type is determined
-by the conversion rules applied to all the function return
-types so it is long double or long double _Complex)
+the result must be casted to the right type
+(otherwise the result type is determined by the conversion
+rules applied to all the function return types so it is long
+double or long double complex except for integral functions)
-this cannot be done in c99 (c11 has _Generic that would help
-but is not yet widely supported), so the typeof extension of
-gcc is used and that ?: has special semantics when one of
-the operands is a null pointer constant
+this cannot be done in c99, so the typeof gcc extension is
+used and that the type of ?: depends on wether an operand is
+a null pointer constant or not
+(in c11 _Generic can be used)
-unfortunately the standard is overly strict about the
-definition of null pointer constants (current gcc does not
-follow the standard but clang does) so we have to use a hack
-to be able to tell integer and floating-point types apart:
-both gcc and clang evaluate sizeof(void) to 1 even though it
-is a constraint violation, we only use this on clang for now
+the c arguments below must be integer constant expressions
+so they can be in null pointer constants
+(__IS_FP above was carefully chosen this way)
-/* predicates that evaluate to integer constant expressions */
-#ifdef __clang__
-/* TODO: __c_IS_FP(1.0) is a constraint violation */
-#define __c_IS_FP(x) (!(sizeof*(__typeof__(0?(int*)0:(void*)__IS_FP(x)))0-1))
-#define __c_IS_FP(x) __IS_FP(x)
-#define __c_IS_CX(x) (__c_IS_FP(x) && sizeof(x) == sizeof((x)+I))
-#define __c_FLTCX(x) (__c_IS_CX(x) && sizeof(x) == sizeof(float complex))
-#define __c_DBLCX(x) (__c_IS_CX(x) && sizeof(x) == sizeof(double complex))
-#define __c_LDBLCX(x) (__c_IS_CX(x) && sizeof(x) == sizeof(long double complex) && sizeof(long double) != sizeof(double))
/* if c then t else void */
#define __type1(c,t) __typeof__(*(0?(t*)0:(void*)!(c)))
/* if c then t1 else t2 */
#define __type2(c,t1,t2) __typeof__(*(0?(__type1(c,t1)*)0:(__type1(!(c),t2)*)0))
/* cast to double when x is integral, otherwise use typeof(x) */
#define __RETCAST(x) ( \
- __type2(__c_IS_FP(x), __typeof__(x), double))
+ __type2(__IS_FP(x), __typeof__(x), double))
/* 2 args case, should work for complex types (cpow) */
#define __RETCAST_2(x, y) ( \
- __type2(__c_IS_FP(x) && __c_IS_FP(y), \
+ __type2(__IS_FP(x) && __IS_FP(y), \
__typeof__((x)+(y)), \
/* 3 args case (fma only) */
#define __RETCAST_3(x, y, z) ( \
- __type2(__c_IS_FP(x) && __c_IS_FP(y) && __c_IS_FP(z), \
+ __type2(__IS_FP(x) && __IS_FP(y) && __IS_FP(z), \
__typeof__((x)+(y)+(z)), \
/* drop complex from the type of x */
/* TODO: wrong when sizeof(long double)==sizeof(double) */
#define __RETCAST_REAL(x) ( \
- __type2(sizeof(__RETCAST(x)0+I)==sizeof(float complex), float, \
- __type2(sizeof(__RETCAST(x)0+I)==sizeof(double complex), double, \
+ __type2(__IS_FP(x) && sizeof((x)+I) == sizeof(float complex), float, \
+ __type2(sizeof((x)+1.0+I) == sizeof(double complex), double, \
long double)))
/* add complex to the type of x */
#define __RETCAST_CX(x) (__typeof__(__RETCAST(x)0+I))