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Date: Wed, 26 Nov 2014 00:19:26 +0100
From: Szabolcs Nagy <>
Subject: Re: [PATCH 1/4] the CMPLX macros must be usable in
 initializations of static variables

* Jens Gustedt <> [2014-11-25 22:23:03 +0100]:
> right for all such compilers is quite a pain. I'll see what clang
> offers, here.

clang has

 static double _Complex z = (double _Complex){x, y};

which is problematic because it is a language extension that
gcc and other c11 compilers wont support most likely

(a compound literal (T){x,y} is a constraint violation for
scalar T, so a sensible c11 compiler will emit diagnostics)

> > and fall back
> > to the compound literal version otherwise (it wont work as static
> > initializer then, but right now the biggest user of CMPLX is most
> > likely musl src/complex/* which dont need it to be constant expr
> > but does rely on proper semantics for infinites and signed zeros)
> If that is so, I'd be in favor of having and using an internal macro
> that uses the compound literal. The compilation of the library
> shouldn't depend too much on compiler versions.

it used to be an internal macro, but i thought it makes sense
to use the new CMPLX instead when it was added to complex.h

but if CMPLX semantics cannot be guaranteed with c99 features
then probably we should go back to the internal macro (and not
define CMPLX at all in complex.h if the semantics is wrong)

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