Swift 项目中的 C++ dylib - dylib 中公开的函数的未定义符号 [英] C++ dylib in Swift project - undefined symbols for function exposed in dylib
问题描述
C++ dylib 暴露如下
C++ dylib exposes as follows
__attribute__((visibility("default"))) int addNumber(int number) {
return 0;
}
在我的 Swift 项目中,我将导入路径目录设置为包含我的 module.map 文件的目录:
in my Swift project, I set the Import Paths dir to the dir containing my module.map file:
module MyLib {
header "myLib.h"
export *
}
我手动将 myLib.h
添加到我的项目中:
I manually add myLib.h
to my project:
#ifndef mylib_h
#define mylib_h
int addNumber(int number);
#endif
我的 main.swift
执行以下操作:
My main.swift
does the following:
import Foundation
import MyLib
print("Hello, World!")
var result = addNumber(3)
当我编译 swift 项目时,我可以看到它链接到我的 dylib (-lMyLib),但是我收到以下错误:
When I compile the swift project, I can see that it links against my dylib (-lMyLib), but I get the following error:
体系结构 x86_64 的未定义符号:_addNumber",引用从:main.o ld 中的 _main:未找到体系结构 x86_64 clang 的符号:错误:链接器命令失败,退出代码为 1(使用 -v 查看调用)
Undefined symbols for architecture x86_64: "_addNumber", referenced from: _main in main.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)
所以虽然它正确链接,但它找不到符号.我已经用 nm
(0000000000000d00 (__TEXT,__text) external addNumber) 和 Hopper 验证了这个函数确实存在于 dylib 中.
So although it's linking correctly, it can't find the symbols.
I've verified both with nm
(0000000000000d00 (__TEXT,__text) external addNumber) and Hopper that this function does exist in the dylib.
推荐答案
在C++库中,你的函数必须用extern "C"
对于 C 链接:
In the C++ library, your function must be marked with extern "C"
for C linkage:
extern "C" __attribute__((visibility("default"))) int addNumber(int number) {
return 0;
}
这样编译器就不会破坏导出的名称.斯威夫特只能调用 C 函数,而不是 C++ 函数.
so that the compiler does not mangle the exported name. Swift can only call C functions, not C++ functions.
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