Build on 10.6.8 Rosetta uses ABSL_RANDOM_HWAES_X64_FLAGS despite OSX_ARCHITECTURES = ppc

[barracuda156]

Describe the bug

I am building abseil on 10.6.8 Rosetta for ppc (well, in fact I has built it, but with an ugly solution of just editing away Intel flags). Despite Cmake correctly recognizing OSX_ARCHITECTURES="ppc", it still pulls out Intel HWAES flags, which obviously cause a failure.
I tried specifying CMAKE_SYSTEM_PROCESSOR=ppc and tried a couple of patches to the source code, but nothing helped.
Removing away flags in question from abseil-abseil-cpp-273292d/absl/copts/GENERATED_AbseilCopts.cmake solved the issue, at least on the surface, but it is clearly a bad solution.

What is required is to ensure ppc is used all through, with no x86 setting pulled over.

This chunk of code causes the problem:

list(APPEND ABSL_RANDOM_HWAES_X64_FLAGS
    "-maes"
    "-msse4.1"
)

What version of Abseil are you using?

10:~ svacchanda$ port -v installed abseil
The following ports are currently installed:
  abseil @20220623.0_0 (active) requested_variants='' platform='darwin 10' archs='ppc' date='2022-07-22T21:38:20+0400'

What operating system and version are you using

10.6.8 Rosetta (build for ppc32), Xcode 3.2.6

What compiler and version are you using?

10:~ svacchanda$ /opt/local/bin/gcc-mp-12 -v
Using built-in specs.
COLLECT_GCC=/opt/local/bin/gcc-mp-12
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/ppc-apple-darwin10/12.1.0/lto-wrapper
Target: ppc-apple-darwin10
Configured with: /opt/local/var/macports/build/_opt_PPCRosettaPorts_lang_gcc12/gcc12/work/gcc-12.1.0/configure --prefix=/opt/local --build=ppc-apple-darwin10 --enable-languages=c,c++,objc,obj-c++,lto,fortran,jit --libdir=/opt/local/lib/gcc12 --includedir=/opt/local/include/gcc12 --infodir=/opt/local/share/info --mandir=/opt/local/share/man --datarootdir=/opt/local/share/gcc-12 --with-local-prefix=/opt/local --with-system-zlib --disable-nls --program-suffix=-mp-12 --with-gxx-include-dir=/opt/local/include/gcc12/c++/ --with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local --with-isl=/opt/local --with-zstd=/opt/local --enable-checking=release --disable-multilib --enable-lto --enable-libstdcxx-time --without-build-config --with-as=/opt/local/bin/as --with-ld=/opt/local/bin/ld --with-ar=/opt/local/bin/ar --with-bugurl=https://trac.macports.org/newticket --enable-host-shared --with-darwin-extra-rpath=/opt/local/lib/libgcc --with-libiconv-prefix=/opt/local --with-tune-cpu=G4 --disable-tls --with-pkgversion='MacPorts gcc12 12.1.0_3'
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.1.0 (MacPorts gcc12 12.1.0_3)

What build system are you using?

I use Macports and cmake-devel 3.24.0-rc4.

[barracuda156]

[ 12%] Building CXX object absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o
cd /opt/local/var/macports/build/_opt_PPCRosettaPorts_devel_abseil/abseil/work/build/absl/random && /opt/local/bin/g++-mp-12 -Drandom_internal_randen_hwaes_impl_EXPORTS -I/opt/local/var/macports/build/_opt_PPCRosettaPorts_devel_abseil/abseil/work/abseil-cpp-20220623.0 -pipe -Os -DNDEBUG -I/opt/local/include -D_GLIBCXX_USE_CXX11_ABI=0 -arch ppc -mmacosx-version-min=10.6 -fPIC -Wall -Wextra -Wcast-qual -Wconversion-null -Wformat-security -Wmissing-declarations -Woverlength-strings -Wpointer-arith -Wundef -Wunused-local-typedefs -Wunused-result -Wvarargs -Wvla -Wwrite-strings -DNOMINMAX -maes -msse4.1 -std=gnu++14 -MD -MT absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o -MF CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o.d -o CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o -c /opt/local/var/macports/build/_opt_PPCRosettaPorts_devel_abseil/abseil/work/abseil-cpp-20220623.0/absl/random/internal/randen_hwaes.cc
g++-mp-12: error: unrecognized command-line option '-maes'
g++-mp-12: error: unrecognized command-line option '-msse4.1'
make[2]: *** [absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o] Error 1
make[2]: Leaving directory `/opt/local/var/macports/build/_opt_PPCRosettaPorts_devel_abseil/abseil/work/build'
make[1]: *** [absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/all] Error 2

[anpol]

Relying on CMAKE_OSX_ARCHITECTURES would be incorrect, the value of this variable is a list of architectures, not a single architecture.

To compile with CMake, you might need add support for your processor, e.g.:

diff --git a/absl/copts/AbseilConfigureCopts.cmake b/absl/copts/AbseilConfigureCopts.cmake
index 73435e99..beff32cf 100644
--- a/absl/copts/AbseilConfigureCopts.cmake
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -66,6 +66,8 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "arm.*|aarch64")
   else()
     message(WARNING "Value of CMAKE_SIZEOF_VOID_P (${CMAKE_SIZEOF_VOID_P}) is not supported.")
   endif()
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc|ppc64")
+  set(ABSL_RANDOM_RANDEN_COPTS "${ABSL_RANDOM_HWAES_PPC_FLAGS}")
 else()
   message(WARNING "Value of CMAKE_SYSTEM_PROCESSOR (${CMAKE_SYSTEM_PROCESSOR}) is unknown and cannot be used to set ABSL_RANDOM_RANDEN_COPTS")
   set(ABSL_RANDOM_RANDEN_COPTS "")

Then set CMAKE_SYSTEM_PROCESSOR=ppc on CMake command line.

[barracuda156]

Then set CMAKE_SYSTEM_PROCESSOR=ppc on CMake command line.

@anpol This is exactly what I tried, and it does not work. Cmake somehow forces cpu_arch instead, and applies Intel AES flags.

I tried now changing my patch from elseif(CMAKE_OSX_ARCHITECTURES MATCHES "ppc|ppc64") to elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc|ppc64"), and that fails.
Here is how it configures:

--->  Configuring abseil
Executing:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_abseil/abseil/work/build" && /opt/local/bin/cmake -G "CodeBlocks - Unix Makefiles" -DCMAKE_BUILD_TYPE=MacPorts -DCMAKE_INSTALL_PREFIX="/opt/local" -DCMAKE_INSTALL_NAME_DIR="/opt/local/lib" -DCMAKE_SYSTEM_PREFIX_PATH="/opt/local;/usr" -DCMAKE_C_COMPILER="$CC" -DCMAKE_CXX_COMPILER="$CXX" -DCMAKE_OBJC_COMPILER="$CC" -DCMAKE_OBJCXX_COMPILER="$CXX" -DCMAKE_POLICY_DEFAULT_CMP0025=NEW -DCMAKE_POLICY_DEFAULT_CMP0060=NEW -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_COLOR_MAKEFILE=ON -DCMAKE_FIND_FRAMEWORK=LAST -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_MAKE_PROGRAM=/usr/bin/make -DCMAKE_MODULE_PATH="/opt/local/share/cmake/Modules" -DCMAKE_PREFIX_PATH="/opt/local/share/cmake/Modules" -DCMAKE_BUILD_WITH_INSTALL_RPATH:BOOL=ON -DCMAKE_INSTALL_RPATH="/opt/local/lib" -Wno-dev -DCMAKE_SYSTEM_PROCESSOR="ppc" -DBUILD_SHARED_LIBS=ON -DCMAKE_CXX_STANDARD=14 -DABSL_PROPAGATE_CXX_STD=ON -DCMAKE_OSX_ARCHITECTURES="ppc" -DCMAKE_OSX_DEPLOYMENT_TARGET="10.6" -DCMAKE_OSX_SYSROOT="/" /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_abseil/abseil/work/abseil-cpp-20220623.1 
-- The CXX compiler identification is GNU 12.2.0

Looks good. And then it fails:

[ 14%] Building CXX object absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o
cd /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_abseil/abseil/work/build/absl/random && /opt/local/bin/g++-mp-12 -Drandom_internal_randen_hwaes_impl_EXPORTS -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_abseil/abseil/work/abseil-cpp-20220623.1 -pipe -Os -DNDEBUG -isystem/opt/local/include/LegacySupport -I/opt/local/include -D_GLIBCXX_USE_CXX11_ABI=0 -arch ppc -mmacosx-version-min=10.6 -fPIC -Wall -Wextra -Wcast-qual -Wconversion-null -Wformat-security -Wmissing-declarations -Woverlength-strings -Wpointer-arith -Wundef -Wunused-local-typedefs -Wunused-result -Wvarargs -Wvla -Wwrite-strings -DNOMINMAX -maes -msse4.1 -std=gnu++14 -MD -MT absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o -MF CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o.d -o CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_devel_abseil/abseil/work/abseil-cpp-20220623.1/absl/random/internal/randen_hwaes.cc
g++-mp-12: error: unrecognized command-line option '-maes'
g++-mp-12: error: unrecognized command-line option '-msse4.1'
make[2]: *** [absl/random/CMakeFiles/random_internal_randen_hwaes_impl.dir/internal/randen_hwaes.cc.o] Error 1

The only way that I found to be working is this: #1272 (the patch quoted there, not PR commits).

[anpol]

Looks like you can't set CMAKE_SYSTEM_PROCESSOR on a CMake command line, because it gets overwritten by CMake when it identifies a host toolchain.

You might need to ask CMake community about setting that variable properly. Probably you need to create a toolchain file. Their docs says that you have to set CMAKE_SYSTEM_NAME to trigger cross-compiling.

[barracuda156]

@anpol Thank you. Well, I have solved the problem for myself via changing to CMAKE_OSX_ARCHITECTURES (in CMakeLists), but if I find a better solution that can be general, I open a separate PR.

P. S. Often passing -DCMAKE_SYSTEM_PROCESSOR= via configure works fine. This is likely an issue of how the build system is set up here, not with Cmake as such.