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Date: Tue, 25 Nov 2014 16:25:00 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: [PATCH 1/4] the CMPLX macros must be usable in
initializations of static variables
* Jens Gustedt <Jens.Gustedt@...ia.fr> [2014-11-25 15:49:39 +0100]:
> diff --git a/include/complex.h b/include/complex.h
> index 13a45c5..3e14e04 100644
> --- a/include/complex.h
> +++ b/include/complex.h
> @@ -112,8 +112,7 @@ long double creall(long double complex);
> #define cimagf(x) __CIMAG(x, float)
> #define cimagl(x) __CIMAG(x, long double)
>
> -#define __CMPLX(x, y, t) \
> - ((union { _Complex t __z; t __xy[2]; }){.__xy = {(x),(y)}}.__z)
hm the compound literal is not a constant expression
that is sad
> +#define __CMPLX(x, y, t) ((t)(x) + _Complex_I*(t)(y))
>
this is only correct if the compiler supports annex g kind of
imaginary type, otherwise it is incorrect for infinites
_Complex_I*INFINITY == (0 + i)*(inf + i*0) == nan + i*inf
so imaginary inf will turn into nan real part
this is what gcc (and i assume clang) does
> #define CMPLX(x, y) __CMPLX(x, y, double)
> #define CMPLXF(x, y) __CMPLX(x, y, float)
> --
> 1.9.1
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