Build fails when cross-compiling

[sorny92]

If you try to cross-compile this package in conan you get the next error:

embedded_python/1.3.2@lumicks/stable: Calling build()

checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
checking for python3.9... no
checking for python3... python3
checking for --enable-universalsdk... no
checking for --with-universal-archs... no
checking MACHDEP... "linux"
checking for gcc... aarch64-linux-gnu-gcc-9
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... configure: error: in `/root/.conan/data/embedded_python/1.3.2/lumicks/stable/build/910f9072af01bd4246171eddd52c50d404399ecf/build':
configure: error: cannot run C compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details
embedded_python/1.3.2@lumicks/stable: 
embedded_python/1.3.2@lumicks/stable: ERROR: Package '910f9072af01bd4246171eddd52c50d404399ecf' build failed
embedded_python/1.3.2@lumicks/stable: WARN: Build folder /root/.conan/data/embedded_python/1.3.2/lumicks/stable/build/910f9072af01bd4246171eddd52c50d404399ecf
ERROR: embedded_python/1.3.2@lumicks/stable: Error in build() method, line 110
        build_helper.build_embedded()
while calling 'build_embedded', line 247
        self._build(self.prefix_dir)
while calling '_build', line 228
        self.conanfile.run(f"../src/configure {config_args}")
        ConanException: Error 1 while executing ../src/configure --enable-shared --prefix=/root/.conan/data/embedded_python/1.3.2/lumicks/stable/build/910f9072af01bd4246171eddd52c50d404399ecf/embedded_python --with-openssl=/root/.conan/data/OpenSSL/1.1.1f/_/_/package/34a6f15abcb5e4a5fe68f8affe1a3a5db07089e2

But the variable --host can't be pass because the arguments are hard-coded on the conanfile.

[dean0x7d]

Could you set up a GitHub action that reproduces this? We could then fix it and the action would serve as CI so we can keep supporting cross-compiled targets.

[sorny92]

Sigh I've been trying to replicate the error to build the CI with actions and I just found out that there's another dependency that does not like arm.
At some point I get:

ERROR: mpdecimal/2.4.2: Invalid configuration: Arch is unsupported

When you check mpdecimal sources you see the next:

    def configure(self):
        if self.settings.arch not in ("x86", "x86_64"):
            raise ConanInvalidConfiguration("Arch is unsupported")
        del self.settings.compiler.libcxx
        del self.settings.compiler.cppstd

So arm is not even considered.
I checked the new conan package and this one neither accepts it.
I'm starting to see that the scope of doing this is much bigger than the priority of doing this.

Maybe I should drop it here to pick it up later when this is actually planned and necessary?

[dean0x7d]

Maybe I should drop it here to pick it up later when this is actually planned and necessary?

Sure, that's perfectly reasonable.

mpdecimal error

For prototyping, you could also try conditionally excluding that dependency for ARM. In that case, Python may either pick a system library that matches (if available) or it will build without the decimal module (the CPython build system will happily build without certain modules). One of those may be an acceptable short-term workaround for prototyping.