musl - ./src/internal/atomic.h:229:14: error: size of array 'a_cas_p_undefined_but_pointer_not

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Message-ID: <20220722091224.344b2b22@windsurf>
Date: Fri, 22 Jul 2022 09:12:24 +0200
From: Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: ./src/internal/atomic.h:229:14: error: size of array
 'a_cas_p_undefined_but_pointer_not_32bit' is negative on PowerPC

Hello,

We've "recently" started in Buildroot the build testing of fully random
configurations, so we're now testing many more cases and seeing new
build failures.

As part of this, we're now seeing build failures of musl on PowerPC
32-bit architectures. So far, we've seen the problem on power4
(-mcpu=power4), power5 (-mcpu=power5) and power6 (-mcpu=power6), 970
(-mcpu=970), power8 (-mcpu=power8), 620 (-mcpu=620), 630 (-mcpu=630).

The failure is:

./src/internal/atomic.h:229:14: error: size of array 'a_cas_p_undefined_but_pointer_not_32bit' is negative
  229 | typedef char a_cas_p_undefined_but_pointer_not_32bit[-sizeof(char) == 0xffffffff ? 1 : -1];
      |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can see the full musl build log at:

  http://autobuild.buildroot.net/results/3f1956fbc1746ac25b537ed023e6393ff715f4c9/build-end.log (power4)
  http://autobuild.buildroot.net/results/eeb3d66480e6fb4cd031e7803859480b6d0c72f3/build-end.log (power5)
  http://autobuild.buildroot.net/results/4e41d2ce80ba56f933b1a4ac2dec367d634b0b54/build-end.log (power6)
  http://autobuild.buildroot.net/results/5c7/5c7f71852b8ad201c0615838b7fa6f8bb15cc55b/build-end.log (970)
  http://autobuild.buildroot.net/results/bac/bac4489b489f9b62b5f00be6a3aaac2db90e4ca1/build-end.log (power8)
  http://autobuild.buildroot.net/results/97c/97c6c4bd683e6c7022a62343888dfa8b9d3bab04/build-end.log (620)
  http://autobuild.buildroot.net/results/e2e/e2ed03711a8f2ae7b80efd56114457f8476449cc/build-end.log (630)

I have not investigated the problem so far. I'm not super familiar with
PowerPC, but it seems like these cores are all 64-bit capable, but here
we build for them in 32-bit mode. Maybe this is the case that isn't
handled or supported by musl?

Thanks a lot for your support!

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com

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