Zig项目导入C++头文件构建可执行文件报错求助

问题背景 #

原本通过zig c++ test.cpp simdjson.cpp -o test可正常编译包含simdjson的C代码，将test.cpp改写为test.zig并编写build.zig后，单独构建simdjson静态库正常，但添加可执行文件构建逻辑后出现C导入失败，报错提示simdjson需要C编译器等一系列错误。

相关代码 #

test.cpp #

#include <iostream>
#include "simdjson.h"
using namespace simdjson;
int main(void) {
    ondemand::parser parser;
    padded_string json = padded_string::load("twitter.json");
    ondemand::document tweets = parser.iterate(json);
    std::cout << uint64_t(tweets["search_metadata"]["count"]) << " results." << std::endl;
}

test.zig #

const std = @import("std");

const json = @cImport({
      @cInclude("simdjson.h");
      });


pub fn main() !void{

const parser = json.ondemand.parser;
const file = json.padded_string.load("twitter.json");
const tw =  parser.iterate(file);
const stdout = std.io.getStdOut().writer();
try stdout.print("Hello, {s}!\n", .{tw});

}

build.zig #

const std = @import("std");

pub fn build(b: *std.build.Builder) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const cflags = [_][]const u8{"-std=c++17", "-fno-sanitize=undefined"};

    const lib = b.addStaticLibrary(.{
        .name = "simdjson",
        .target = target,
        .optimize = optimize,
        .link_libc = true,
    });

    lib.linkLibCpp();
    lib.addCSourceFile(.{
    .file = std.Build.FileSource.relative("simdjson.cpp"),
    .flags = &cflags
    });
    lib.addIncludePath(.{ .path = "./header" });
    lib.installHeader("./header/simdjson.h", "simdjson.h");
    //b.installArtifact(lib);

    const exe = b.addExecutable(.{
        .name = "exe",
            .root_source_file = .{ .path = "test.zig" },
            .target = target,
            .optimize = optimize,
        });

    exe.linkLibrary(lib);
    exe.linkLibCpp();
    exe.addCSourceFile(.{
            .file = std.Build.FileSource.relative("simdjson.cpp"),
            .flags = &cflags
            });
            //exe.addIncludePath(.{ .path = "./header" });
    b.installArtifact(exe);
}

错误日志 #

test.zig:3:14: error: C import failed
const json = @cImport({
             ^~~~~~~~
referenced by:
    main: test.zig:11:16
    callMain: /home/mhn/zig/lib/std/start.zig:583:32
    remaining reference traces hidden; use '-freference-trace' to see all reference traces
/home/mhn/zig/lib/libcxx/include/__verbose_abort:20:1: error: unknown type name '_LIBCPP_BEGIN_NAMESPACE_STD'
_LIBCPP_BEGIN_NAMESPACE_STD
^
/home/mhn/zig/lib/libcxx/include/__verbose_abort:24:17: error: expected ';' after top level declarator
_LIBCPP_NORETURN _LIBCPP_AVAILABILITY_VERBOSE_ABORT _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_ATTRIBUTE_FORMAT(__printf__, 1, 2)
                ^
/home/mhn/zig/lib/libcxx/include/__verbose_abort:58:1: error: unknown type name '_LIBCPP_END_NAMESPACE_STD'
_LIBCPP_END_NAMESPACE_STD
^
/home/mhn/Projects/zig-build-test/zig-out/include/simdjson.h:52:2: error: simdjson requires a C++ compiler
#error simdjson requires a C++ compiler
 ^
/home/mhn/Projects/zig-build-test/zig-out/include/simdjson.h:79:2: error: simdjson requires a compiler compliant with the C++11 standard
#error simdjson requires a compiler compliant with the C++11 standard
 ^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:18:1: error: unknown type name '_LIBCPP_BEGIN_NAMESPACE_STD'
_LIBCPP_BEGIN_NAMESPACE_STD
^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:20:9: error: expected ';' after top level declarator
template <bool, class _Tp = void>
        ^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:22:1: error: unknown type name 'template'
template <class _Tp>
^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:22:10: error: expected identifier or '('
template <class _Tp>
         ^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:27:1: error: unknown type name 'template'
template <bool _Bp, class _Tp = void>
^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:27:10: error: expected identifier or '('
template <bool _Bp, class _Tp = void>
         ^
/home/mhn/zig/lib/libcxx/include/__type_traits/enable_if.h:35:1: error: unknown type name '_LIBCPP_END_NAMESPACE_STD'
_LIBCPP_END_NAMESPACE_STD
^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:18:28: error: expected ';' after top level declarator
_LIBCPP_BEGIN_NAMESPACE_STD
                           ^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:31:1: error: unknown type name 'template'
template <class _Tp, _Tp __v>
^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:31:10: error: expected identifier or '('
template <class _Tp, _Tp __v>
         ^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:34:9: error: unknown type name 'integral_constant'
typedef integral_constant<bool, true> true_type;
        ^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:34:26: error: expected identifier or '('
typedef integral_constant<bool, true> true_type;
                         ^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:35:9: error: unknown type name 'integral_constant'
typedef integral_constant<bool, false> false_type;
        ^
/home/mhn/zig/lib/libcxx/include/__type_traits/integral_constant.h:35:26: error: expected identifier or '('
typedef integral_constant<bool, false> false_type;
                         ^
error: too many errors emitted, stopping now

解决方案 #

1. 修复@cImport的C++编译模式问题 #

@cImport默认以C编译器模式解析头文件，无法处理C语法。需要在@cImport块中添加C编译标志，指定用C++标准解析头文件：

const json = @cImport({
    @cFlags("-std=c++17");
    @cInclude("simdjson.h");
});

2. 移除build.zig中的冗余编译逻辑 #

exe已经链接了编译好的simdjson静态库，不需要重复添加simdjson.cpp的编译，删除以下代码：

exe.addCSourceFile(.{
        .file = std.Build.FileSource.relative("simdjson.cpp"),
        .flags = &cflags
        });

同时为exe添加simdjson的头文件路径，取消注释这一行：

exe.addIncludePath(.{ .path = "./header" });

3. 修正test.zig中C++类的调用方式 #

simdjson的命名空间是simdjson，Zig中需要通过json.simdjson访问；另外C++类的成员函数需要通过实例指针调用，修正后的test.zig如下：

const std = @import("std");

const json = @cImport({
    @cFlags("-std=c++17");
    @cInclude("simdjson.h");
});

pub fn main() !void {
    var parser = json.simdjson.ondemand.parser{};
    const file = try json.simdjson.padded_string.load("twitter.json");
    defer file.deinit();

    const tweets = try parser.iterate(file);
    const count = tweets.get_object().?.get_object("search_metadata").?.get_uint64("count").?;

    const stdout = std.io.getStdOut().writer();
    try stdout.print("{d} results.\n", .{count});
}

4. 调整build.zig中静态库的链接设置 #

静态库不需要link_libc，移除lib.link_libc = true;，保持lib.linkLibCpp();即可。

最终修正后的build.zig：

const std = @import("std");

pub fn build(b: *std.build.Builder) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    const cflags = [_][]const u8{"-std=c++17", "-fno-sanitize=undefined"};

    const lib = b.addStaticLibrary(.{
        .name = "simdjson",
        .target = target,
        .optimize = optimize,
    });

    lib.linkLibCpp();
    lib.addCSourceFile(.{
        .file = std.Build.FileSource.relative("simdjson.cpp"),
        .flags = &cflags
    });
    lib.addIncludePath(.{ .path = "./header" });
    lib.installHeader("./header/simdjson.h", "simdjson.h");

    const exe = b.addExecutable(.{
        .name = "exe",
        .root_source_file = .{ .path = "test.zig" },
        .target = target,
        .optimize = optimize,
    });

    exe.linkLibrary(lib);
    exe.linkLibCpp();
    exe.addIncludePath(.{ .path = "./header" });
    b.installArtifact(exe);
}

内容的提问来源于stack exchange，提问作者mhn70