使用Bazel编译soplex时无法识别GMP依赖的问题求助

问题描述 #

我正在开发一个C项目，目标是用Bazel下载并编译所有外部依赖。借助rules_foreign_cc处理非Bazel构建的C库，但编译soplex时遇到问题：soplex依赖GMP和zlib，zlib能被cmake规则识别，但GMP完全被忽略，编译日志提示缺失GMP_INCLUDE_DIRS和GMP_LIBRARIES。

系统信息：Ubuntu，ldd 2.35，g++ 11.4.0，C++17标准。

现有BUILD文件如下：

soplex.BUILD.bazel #

load("@rules_foreign_cc//foreign_cc:defs.bzl", "cmake")

make(
    name = "soplex",
    lib_source = ":all_srcs",
    lib_name = "libsoplex",
    cache_entries = {
        "GMP": "on",
    },
    deps = ["@zlib", "@gmp//:gmpxx"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "all_srcs",
    srcs = glob(["**"]),
    visibility = ["//visibility:private"],
)

zlib.BUILD.bazel #

cc_library("zlib",
# ...
)

gmp.BUILD.bazel #

load("@rules_foreign_cc//foreign_cc:defs.bzl", "configure_make")

configure_make(
    name = "gmp",
    configure_options = ["--with-pic"],
    lib_name = "libgmp",
    lib_source = ":all_srcs",
    visibility = ["//visibility:public"],
)

configure_make(
    name = "gmpxx",
    configure_options = ["--enable-cxx"],
    env = {
        "CXX": "g++",
        "CXXFLAGS": "-lstdc++",
    },
    lib_name = "libgmpxx",
    lib_source = ":all_srcs",
    visibility = ["//visibility:public"],
    deps = [":gmp"],
)

filegroup(
    name = "all_srcs",
    srcs = glob(["**"]),
    visibility = ["//visibility:private"],
)

解决方案 #

1. 改用cmake规则适配soplex的CMake构建 #

soplex官方提供CMakeLists.txt，使用cmake规则替代make规则能更好地处理依赖检测，同时手动传递GMP的路径变量给CMake。

修改后的soplex.BUILD.bazel：

load("@rules_foreign_cc//foreign_cc:defs.bzl", "cmake")

cmake(
    name = "soplex",
    lib_source = ":all_srcs",
    lib_name = "libsoplex",
    cache_entries = {
        "GMP": "ON",
        # 手动指定GMP的头文件目录和库文件
        "GMP_INCLUDE_DIRS": "@gmp//:include",
        "GMP_LIBRARIES": "@gmp//:gmpxx;@gmp//:gmp",
    },
    cmake_options = [
        "-DCMAKE_BUILD_TYPE=Release",
        "-DCMAKE_CXX_STANDARD=17",
    ],
    deps = ["@zlib", "@gmp//:gmpxx", "@gmp//:gmp"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "all_srcs",
    srcs = glob(["**"]),
    visibility = ["//visibility:private"],
)

2. 完善GMP的BUILD配置，导出头文件 #

确保GMP构建时生成位置无关代码，并明确导出头文件目录，让Bazel和CMake能正确找到头文件：

修改后的gmp.BUILD.bazel：

load("@rules_foreign_cc//foreign_cc:defs.bzl", "configure_make")

configure_make(
    name = "gmp",
    configure_options = ["--with-pic"],
    lib_name = "libgmp",
    lib_source = ":all_srcs",
    # 导出头文件目录，让依赖能找到gmp.h
    out_include_dirs = ["include"],
    visibility = ["//visibility:public"],
)

configure_make(
    name = "gmpxx",
    configure_options = ["--enable-cxx", "--with-pic"],
    env = {
        "CXX": "g++",
        "CXXFLAGS": "-std=c++17 -lstdc++",
    },
    lib_name = "libgmpxx",
    lib_source = ":all_srcs",
    out_include_dirs = ["include"],
    visibility = ["//visibility:public"],
    deps = [":gmp"],
)

filegroup(
    name = "all_srcs",
    srcs = glob(["**"]),
    visibility = ["//visibility:private"],
)

3. 关键注意点 #

• rules_foreign_cc的deps仅控制Bazel的依赖构建顺序，不会自动将依赖的路径注入到外部构建系统（如CMake），必须手动通过cache_entries或cmake_options传递必要的变量。
• 手动指定GMP_INCLUDE_DIRS和GMP_LIBRARIES可以绕过CMake的find_package(GMP)自动检测，直接强制使用Bazel构建的GMP库。
• 给GMP添加--with-pic确保生成位置无关代码，避免链接soplex时出现重定位错误。

内容的提问来源于stack exchange，提问作者Tend