[Bazel]自定义规则实现将多个静态库合并为一个动态库或静态库

$ gcc -shared -fPIC -Wl,--whole-archive libA.a libB.a libC.a -Wl,--no-whole-archive -Wl,-soname -o libcombined.so

$ gcc -shared -fPIC -Wl,--whole-archive libA.a libB.a libC.a -Wl,--no-whole-archive  -Wl,-soname -o libcombined.so

$ cd temp
$ ar x libA.a
$ ar x libB.a
$ ar x libC.a
$ ar rc libcombined.a *.o

# MacOS系统
$ libtool -static -o libcombined.a libA.a libB.a libC.a

$ sudo apt-get install libtool-bin
# 生成的libcombined.a ar -x 解压出来是 libA.a libB.a libC.a ，而不是 *.o 文件。
$ libtool --mode=link gcc -o libcombined.a libA.a libB.a libC.a
# 这样可以指定生成路径，但是 *.o 的生成还是需要 ar -x 来生成
$ libtool --mode=link gcc -o libcombined.a *.o

my_cc_combine = rule(
    implementation = _combine_impl,
    attrs = {
        "genstatic" : attr.bool(default = False),
        "deps": attr.label_list(),
    }
)

my_cc_combine = rule(
    implementation = _combine_impl,
    attrs = {
        "_cc_toolchain": attr.label(default = Label("@bazel_tools//tools/cpp:current_cc_toolchain")),
        "genstatic" : attr.bool(default = False),
        "deps": attr.label_list(),
    }
)

x = dep_target[CcInfo].linking_context.linker_inputs.to_list()
for linker_in in x:
    # <LinkerInput(owner=//libA:A, libraries=[<LibraryToLink(pic_objects=[File:[[<execution_root>]bazel-out/k8-fastbuild/bin]libA/_objs/A/liba.pic.o], pic_static_library=File:[[<execution_root>]bazel-out/k8-fastbuild/bin]libA/libA.a, alwayslink=false)>, ], userLinkFlags=[], nonCodeInputs=[])>
    for linker_in_lib in linker_in.libraries:
        # <generated file libE/libA.a>
        # <generated file libE/libE.a>
        internal_link_lib = linker_in_lib.pic_static_library
        # <source file 3rdparty/libs/libD.a>
        external_link_lib = linker_in_lib.static_library
        

load("@bazel_tools//tools/cpp:toolchain_utils.bzl", "find_cpp_toolchain")

def _combine_impl(ctx):
    cc_toolchain = find_cpp_toolchain(ctx)    

    target_list = []
    for dep_target in ctx.attr.deps:        
        # CcInfo, InstrumentedFilesInfo, OutputGroupInfo      
        cc_info_linker_inputs = dep_target[CcInfo].linking_context.linker_inputs

        target_dirname_list = []
        for linker_in in cc_info_linker_inputs.to_list():            
            for linker_in_lib in linker_in.libraries:                
                if linker_in_lib.pic_static_library != None:
                    target_list += [linker_in_lib.pic_static_library]                    
                if linker_in_lib.static_library != None:
                    target_list += [linker_in_lib.static_library]
    
    output = ctx.outputs.output
    if ctx.attr.genstatic:
        cp_command  = ""       
        processed_list = []
        processed_path_list = []
        for dep in target_list:
            cp_command += "cp -a " + dep.path + " " + output.dirname + "/ && "
            processed = ctx.actions.declare_file(dep.basename)
            processed_list += [processed]
            processed_path_list += [dep.path]
        cp_command += "echo 'starting to run shell'"
        processed_path_list += [output.path]
  
        ctx.actions.run_shell(
            outputs = processed_list,
            inputs = target_list,
            command = cp_command,
        )

        command = "cd {} && ar -x {} {}".format(
                output.dirname,
                " && ar -x ".join([dep.basename for dep in target_list]),
                " && ar -rc libauto.a *.o"
            )
        print("command = ", command)
        ctx.actions.run_shell(
            outputs = [output],
            inputs = processed_list,
            command = command,
        )
    else:
        command = "export PATH=$PATH:{} && {} -shared -fPIC -Wl,--whole-archive {} -Wl,--no-whole-archive -Wl,-soname -o {}".format(
            cc_toolchain.ld_executable,
            cc_toolchain.compiler_executable,
            " ".join([dep.path for dep in target_list]),
            output.path)
        print("command = ", command)
        ctx.actions.run_shell(
            outputs = [output],
            inputs = target_list,
            command = command,
        )

my_cc_combine = rule(
    implementation = _combine_impl,
    attrs = {
        "_cc_toolchain": attr.label(default = Label("@bazel_tools//tools/cpp:current_cc_toolchain")),
        "genstatic" : attr.bool(default = False),
        "deps": attr.label_list(),
        "output": attr.output()
    },
)

load(":my_cc_combine.bzl", "my_cc_combine")

my_cc_combine(
    name = "hello_combined",
    # 这里将所有的静态库合并成一个静态库
    genstatic = True,
    output = "libcombined.a",
    deps = ["//libA:A", "//libB:B", "//libC:C"]
)