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Date: Wed, 13 May 2020 13:27:19 -0400
From: Rich Felker <>
To: John Arnold <>
Cc: Anders Magnusson <>,,
Subject: Re: Re: [Pcc] PCC unable to build musl 1.2.0 (and
 likely earlier)

On Wed, May 13, 2020 at 12:00:24PM -0500, John Arnold wrote:
> > Can you please sen med the offending line?
> include/limits.h:10:
> #if '\xff' > 0
> > Same here, can you send me the line that causes the bug?
> > And true, __builtin_complex is not recognized in pcc.
> catan.c:105 is:
> w = CMPLX(w, 0.25 * log(a));
> which pcc -E expands to:
> w = ((union { _Complex double __z; double __xy[2]; }){.__xy =
> {(w),(0.25 * log(a))}}.__z);

Where are you getting this from? There has not been any union compound
literal like that since 2014 because it was found not to be valid in
constant expressions and CMPLX is required to produce a constant
expression. Commit 5ff2a118c64224789b7286830912425e58831b2b is
informative, and the message notes that CMPLX is a C11 feature, so
since the musl source is supposed to build with just C99 (+ minimal
extensions) perhaps we should drop internal use of CMPLX anyway...

> Rich is right, changing line 105 to:
> w = w+0.25*log(a)*I
> solves the problem, but then we get the bad register name `%%ax' error
> when trying to assemble catan.o.

Are you sure? There's no asm in catan.c. If %%ax appears in what gets
passed to the assembled for this file, it's emitted by PCC itself.

> Running make -j also reveals that this assembly error pops up in more
> places, at least also catanl.o, catanf.o, and csqrt.o.

In that case it sounds like it very well might be a bug in PCC's
codegen rather than anything in our inline asm (elsewhere) which I
originally suspected it was.


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