Create cc_compiled_module rule

[igormcoelho]

This rule allows to direct inject some CMI into the project... like a precompiled .pcm of the std... I managed to use import std; with this trick.

TODO: must update defs.blz as follows:

load("//cc_module/private:cc_module.bzl",
     _cc_module = "cc_module",
     _cc_header_module = "cc_header_module",
     _cc_compiled_module = "cc_compiled_module",
     _cc_module_binary = "cc_module_binary",
     _cc_module_library = "cc_module_library",
)

cc_module = _cc_module
cc_header_module = _cc_header_module
cc_compiled_module = _cc_compiled_module
cc_module_binary = _cc_module_binary
cc_module_library = _cc_module_library

Then, as long as the user precompiles the std, everything works fine. Too bad I couldn't automate the precompilation of std, because the file comes from the system, not from bazel...

I do std.pcm manually on example/hello-world/Makefile:

CXX = clang++-19
CXXFLAGS += -std=c++23 -stdlib=libc++ -U_FORTIFY_SOURCE -fstack-protector -Wall -Wthread-safety -Wself-assign -Wunused-but-set-parameter -Wno-free-nonheap-object -fcolor-diagnostics -fno-omit-frame-pointer '-std=c++23' -fPIC

hello_world: std.pcm hello.pcm main.cc
	$(CXX) $(CXXFLAGS) -fmodule-file=std=std.pcm -fmodule-file=hello=hello.pcm  -o $@ $^

std.pcm: /usr/lib/llvm-19/share/libc++/v1/std.cppm 
	$(CXX) $(CXXFLAGS) -Wno-reserved-identifier -Wno-reserved-module-identifier --precompile -o $@ $^

hello.pcm: hello.cppm std.pcm
	$(CXX) $(CXXFLAGS) -fmodule-file=std=std.pcm -Wno-reserved-identifier -Wno-reserved-module-identifier --precompile -o $@ $^

clean:
	rm -rf *.pcm
	rm -rf hello_world

Then, example is just:

// main.cc
import hello;

//import <string_view>;
import std;

int main() {
  say_hello("world");
  return 0;
}

// hello.cppm
export module hello;

//import <iostream>;
//import <string_view>;
import std;

// the module purview starts here
// provide a function to users by exporting it
export inline void say_hello(std::string_view const &name)
{
  std::cout << "Hello " << name << "!\n";
}

And BUILD for examples/hello-world:

load("//cc_module:defs.bzl", "cc_module", "cc_compiled_module", "cc_module_binary")

cc_module(
    name = "hello",
    src = "hello.cppm",
    copts = [
        "-fmodule-file=std=example/hello-world/std.pcm",
        "-stdlib=libc++",
        "-std=c++23",
    ],
    deps = [":std"],
)


cc_module_binary(
    name = "hello_world",
    srcs = [
        "main.cc",
    ],
    deps = [
        ":hello",
        ":std"
    ],
    copts = [
        "-fmodule-file=std=example/hello-world/std.pcm",
        "-stdlib=libc++",
        "-std=c++23",
    ],
    linkopts = [
        "-stdlib=libc++",
    ],
)

cc_compiled_module(
    name="std",
    cmi="std.pcm"
)

Command will work fine: bazel build //example/hello-world:hello_world

Tested on Bazel 5 up to 8.

On my '.bazelrc` I forced clang compiler:

build --action_env=CC=/usr/bin/clang++-19
build --action_env=CXX=/usr/bin/clang++-19