Build error on power architecture

[eschnett]

I am cross-building zlib-ng for a powerpc64le-linux-gnu system. The build fails with the error message

[16:27:09] /opt/bin/powerpc64le-linux-gnu-libgfortran3-cxx03/powerpc64le-linux-gnu-gcc --sysroot=/opt/powerpc64le-linux-gnu/powerpc64le-linux-gnu/sys-root/ -DHAVE_ALIGNED_ALLOC -DHAVE_ATTRIBUTE_ALIGNED -DHAVE_BUILTIN_CTZ -DHAVE_BUILTIN_CTZLL -DHAVE_POSIX_MEMALIGN -DHAVE_SYMVER -DHAVE_SYS_AUXV_H -DHAVE_VISIBILITY_HIDDEN -DHAVE_VISIBILITY_INTERNAL -DPOWER_FEATURES -DPPC_FEATURES -DPPC_VMX -DWITH_GZFILEOP -DZLIBNG_NATIVE_API -DZLIB_DLL -D_LARGEFILE64_SOURCE=1 -D__USE_LARGEFILE64 -I/workspace/srcdir/zlib-ng/build -I/workspace/srcdir/zlib-ng -O2 -DNDEBUG -fPIC -Wall -std=c11 -MD -MT CMakeFiles/zlib.dir/gzwrite.c.o -MF CMakeFiles/zlib.dir/gzwrite.c.o.d -o CMakeFiles/zlib.dir/gzwrite.c.o -c /workspace/srcdir/zlib-ng/gzwrite.c
  | [16:27:09] /workspace/srcdir/zlib-ng/arch/power/power_features.c: In function ‘power_check_features’:
  | [16:27:09] /workspace/srcdir/zlib-ng/arch/power/power_features.c:34:24: error: ‘AT_HWCAP2’ undeclared (first use in this function)
  | [16:27:09]      hwcap2 = getauxval(AT_HWCAP2);
  | [16:27:09]                         ^
  | [16:27:09] /workspace/srcdir/zlib-ng/arch/power/power_features.c:34:24: note: each undeclared identifier is reported only once for each function it appears in
  | [16:27:09] /workspace/srcdir/zlib-ng/arch/power/power_features.c:30:19: warning: variable ‘hwcap2’ set but not used [-Wunused-but-set-variable]
  | [16:27:09]      unsigned long hwcap2;
  | [16:27:09]                    ^
  | [16:27:09] make[2]: *** [CMakeFiles/zlib.dir/build.make:454: CMakeFiles/zlib.dir/arch/power/power_features.c.o] Error 1
  | [16:27:09] make[2]: *** Waiting for unfinished jobs....
  | [16:27:10] make[2]: Leaving directory '/workspace/srcdir/zlib-ng/build'
  | [16:27:10] make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/zlib.dir/all] Error 2
  | [16:27:10] make[1]: Leaving directory '/workspace/srcdir/zlib-ng/build'
  | [16:27:10] make: *** [Makefile:156: all] Error 2
 ```

I think the statement `#include <linux/auxvec.h>` is missing in this source file.

[eschnett]

I have since received this feedback from @giordano (see JuliaPackaging/Yggdrasil#8007): "I think the problem is that we target an old glibc (2.17), which doesn't have that header, but the corresponding linux header does that job. Unless upstream plans to support old glibc, it's probably fair for us to ship the patch, we do it elsewhere as well."

In other words, this issue might be caused by us using an old version of glibc, and if so, please disregard this issue.

[mtl1979]

In normal cross-build toolchain in Debian/Ubuntu, AT_HWCAP2 is defined in both bits/auxv.h (included by sys/auxv.h) and linux/auxvec.h. We already detect some unusual toolchains during configure time, but I can't fix for every possible toolchain unless I have the specific toolchain, that fails to build, on my build cluster.

This seems regression from 2fa631e.

[nmoinvaz]

@eschnett, a regression has been fixed in develop branch if you want to try it out.

[eschnett]

Thanks. I was setting up a build recipe for Julia language bindings, and we usually stay with released versions there. I'm looking forward to needing fewer patches then!