py-grpcio: error: invalid argument '-std=c++11' not allowed with 'C'

[ryandesign (Ryan Carsten Schmidt)]

​py-grpcio does not build:

/opt/local/bin/clang-mp-9.0 -fno-strict-aliasing -fno-common -dynamic -pipe -Os -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -arch i386 -isysroot/ -D_WIN32_WINNT=1536 -DOPENSSL_NO_ASM=1 -DGPR_BACKWARDS_COMPATIBILITY_MODE=1 -DHAVE_CONFIG_H=1 -DGRPC_ENABLE_FORK_SUPPORT=1 -DPyMODINIT_FUNC=extern "C" __attribute__((visibility ("default"))) void -DGRPC_POSIX_FORK_ALLOW_PTHREAD_ATFORK=1 -Isrc/python/grpcio -Iinclude -I. -Ithird_party/abseil-cpp -Ithird_party/address_sorting/include -I/opt/local/include -Ithird_party/re2 -I/opt/local/include/openssl -Ithird_party/upb -Isrc/core/ext/upb-generated -Isrc/core/ext/upbdefs-generated -I/opt/local/include -I/opt/local/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c src/core/ext/upbdefs-generated/udpa/annotations/migrate.upbdefs.c -o python_build/temp.macosx-10.10-i386-2.7/src/core/ext/upbdefs-generated/udpa/annotations/migrate.upbdefs.o -std=c++11 -stdlib=libc++ -fvisibility=hidden -fno-wrapv -fno-exceptions -pthread
error: invalid argument '-std=c++11' not allowed with 'C'

It's trying to give the -std=c++11 -stdlib=libc++ flags to the C compiler. C compilers don't understand those flags. Only C++ compilers do.

This probably relates to the fact that Python does not support modules written in C++. It's unfortunate that the developers of py-grpcio decided to write a module in C++ despite the fact that Python doesn't support it.

[jmroot (Joshua Root)]

Might be able to work around it by adding -xc++ to the flags.

[mascguy (Christopher Nielsen)]

With the latest version of the port, the complaint now relates to std=c++14. But same fundamental issue.

Sounds like it's worth trying Josh's suggestion from comment:1 though:

Might be able to work around it by adding -xc++ to the flags.

[jmroot (Joshua Root)]

If it's all C++, then the workaround used in py-re2 could work. But if there's a mix of C and C++, there's no way to specify the correct compiler for each from outside the build system, and you're probably looking at some patching.

[ryandesign (Ryan Carsten Schmidt)]

Now reported to the developers: ​https://github.com/grpc/grpc/issues/33923

[jmroot (Joshua Root)]

So looks like this was probably fixed upstream by ​https://github.com/grpc/grpc/commit/31fc452b68e429c029f00b5fcc54292a303be0c6

[mascguy (Christopher Nielsen)]

Replying to jmroot:

So looks like this was probably fixed upstream by ​https://github.com/grpc/grpc/commit/31fc452b68e429c029f00b5fcc54292a303be0c6

Haven't looked too closely at the Python details yet. But I did try building py310-grpcio on 10.9, with that patch. And no luck.

Build log attached; filename: py310-grpcio-build-10.9-patched.log.gz.

If anyone's interested in taking a quick look, I'd love to hear folks' thoughts! Otherwise, I'll try to find some time to dig into this further, over the coming days...

[mascguy (Christopher Nielsen)]

Replying to jmroot:

So looks like this was probably fixed upstream by ​https://github.com/grpc/grpc/commit/31fc452b68e429c029f00b5fcc54292a303be0c6

The patch I used - based on that commit - is also attached; filename: patch-python-respect-cc-variable.diff.

[jmroot (Joshua Root)]

I don't see the patch being applied in that log. Did you change the patch phase override to a post-patch?

[mascguy (Christopher Nielsen)]

Replying to jmroot:

I don't see the patch being applied in that log. Did you change the patch phase override to a post-patch?

Ah, nope, that would certainly help! With that additional change in play, the build looks good now. Thanks for the catch Josh!

[Christopher Nielsen <mascguy@…>]

In f931cfa55254ec9928d5b9a7103f11cca7b68f35/macports-ports (master):

py-grpcio*: patch to fix C compiler handling

Fixes: #62208

[mascguy (Christopher Nielsen)]

Replying to ryandesign:

Now reported to the developers: ​https://github.com/grpc/grpc/issues/33923

I commented on the issue, letting folks know that the upstream patch fixes the issue. Ryan, do you want to close that?