gl_signbitf (float arg)
{
#if defined FLT_SIGNBIT_WORD && defined FLT_SIGNBIT_BIT
+ /* The use of a union to extract the bits of the representation of a
+ 'long double' is safe in practice, despite of the "aliasing rules" of
+ C99, because the GCC docs say
+ "Even with '-fstrict-aliasing', type-punning is allowed, provided the
+ memory is accessed through the union type."
+ and similarly for other compilers. */
# define NWORDS \
((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
union { float value; unsigned int word[NWORDS]; } m;
m.value = arg;
return (m.word[FLT_SIGNBIT_WORD] >> FLT_SIGNBIT_BIT) & 1;
+#elif HAVE_COPYSIGNF_IN_LIBC
+ return copysignf (1.0f, arg) < 0;
#else
/* This does not do the right thing for NaN, but this is irrelevant for
most use cases. */