英文:
Go can't call c++ function
问题
我一直在使用cgo来在Go和C之间进行接口调用。然而，当我尝试在Go和C++之间做同样的事情时，每次尝试调用函数时都会出现编译错误。在代码目录中使用go build .命令时，我得到了以下错误信息：
./main.go: In function 'void _cgo_3612c872201c_Cfunc_getint(void*)':
./main.go:48:53: error: invalid conversion from 'void*' to '_cgo_3612c872201c_Cfunc_getint(void*)::<anonymous struct>*' [-fpermissive]
./main.go:54:4: error: invalid conversion from 'void*' to '_cgo_3612c872201c_Cfunc_getint(void*)::<anonymous struct>*' [-fpermissive]
我在下面放了一个非常简单的示例，展示了这个问题。
main.go:
package main
/*
#cgo CFLAGS: -x c++
int getint()
{
return 1;
}
*/
import "C"
import (
"fmt"
)
func main() {
fmt.Println(C.getint())
}
有人知道这是否是cgo的一个bug，还是我编写代码的问题吗？根据cgo文档，支持C++。我正在使用Go版本1.7.5，操作系统是linux/amd64。
非常感谢！
英文:
I have been using cgo to interface between Go and C. However, when trying to do the same for Go and C++, I get a compile error every time I attempt to call a function. Using go build . from the code's directory, I get the following errors:
./main.go: In function 'void _cgo_3612c872201c_Cfunc_getint(void*)':
./main.go:48:53: error: invalid conversion from 'void*' to '_cgo_3612c872201c_Cfunc_getint(void*)::<anonymous struct>*' [-fpermissive]
./main.go:54:4: error: invalid conversion from 'void*' to '_cgo_3612c872201c_Cfunc_getint(void*)::<anonymous struct>*' [-fpermissive]
I've put a super simple example below which shows the problem.
main.go:
package main
/*
#cgo CFLAGS: -x c++
int getint()
{
return 1;
}
*/
import "C"
import (
"fmt"
)
func main() {
fmt.Println(C.getint())
}
Does anyone know if this is a bug in cgo, or something wrong with how I wrote the code? According to the cgo documentation, C++ is supported. I'm using Go version 1.7.5 for linux/amd64.
Thanks so much!
答案1
得分: 3
我可能错了，但我认为cgo只在某种程度上支持C++，它知道如何在非Go文件上调用C++编译器，这些文件看起来像包含C++源代码，仅此而已。
问题在于C++编译器对从编译文件中导出的符号使用所谓的“名称修饰”（mangling）。导出符号最初只用于类似C的语言，其中可以导出的只有普通函数和变量，但C++添加了类和函数重载，并且为了从编译（“对象”）文件中导出这些符号，C++编译器需要使用特定的模式对类的名称和参数类型进行编码。更糟糕的是，每个C++编译器品牌都使用自己的名称修饰模式。
因此，我认为虽然cgo能够编译C++代码，但它假设您的C++文件中导出的所有符号（供Go使用）都包装在extern "C" { ... }中（参见这里）。
如果您需要调用“本地”的C++导出内容，您需要使用SWIG。
英文:
I may be wrong, but I think cgo supports C++ only in the sense it knows how to invoke a C++ compiler on the non-Go files which looks like containing C++ source code, and that's all.
The problem is that C++ compilers use so-called "mangling" for the symbols made exported from the compiled files. Exporting symbols were originally
intended only for C-like languages, where all which can be exported are plain
functions and variables, but C++ adds classes and function overloading,
and to export such symbols from compiled ("object") files, a C++ compiler
needs to "mangle" them using certain schema to encode names of classes
and types of arguments in these names. What's worse, each C++ compiler
brand uses its own mangling schemas.
So I think while cgo is able to compile C++ code, it sort of assumes that
all the symbols exported (to be used by Go) in your C++ files are
wrapped in extern "C" { ... } (see this).
If you need calls to "native" C++ exported stuff, you'd need to use
SWIG I reckon.
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