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__extension__ union { double d; int i[2]; } u = { d: -0.25 };
/* This assumes the endianness of words in a long long is the same as
that for doubles, which doesn't hold for a few platforms, but we
can probably special case them here, as appropriate. */
long long endianness_test = 1;
#define MSW (*(int*)&endianness_test)
int
signbit(double x)
{
__extension__ union { double d; int i[2]; } u = { d: x };
return u.i[MSW] < 0;
}
int main(void)
{
if (2*sizeof(int) != sizeof(double) || u.i[MSW] >= 0)
exit(0);
if (!signbit(-0.25))
abort();
exit(0);
}
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