GCC链接/符号名称与C ++和汇编程序文件 [英] GCC linking / symbol name mangling with C++ and assembler files

问题描述

我在编译和链接用汇编程序编写的库和我在C ++中的程序代码时遇到了一些麻烦。在我的情况下，它是为使用avr-gcc套件的AVR微控制器，但我想这个问题将适用于GCC一般。

I'm having some trouble compiling and linking a library that's written in assembler with my program code which is in C++. In my case it's for an AVR microcontroller using the avr-gcc suite, but I imagine this problem would apply to GCC generally.

我可以从C ++源码和程序集中得到.o文件，但链接它们会产生错误：

I can get .o files built from the C++ source and assembly, but linking them gives the error:

> avr-gcc -mmcu=attiny84 -lm -o obj\AvrTest.elf obj\Main.o obj\i2cmaster.o
obj\Main.o: In function `main':
Main.cpp:(.text+0x0): undefined reference to `i2c_init()'

uber-simple Main.cpp 代码：

Here's the uber-simple Main.cpp code:

#include "i2cmaster.h"
void main() { 
    i2c_init();
    while ( true ) {
    }
}

i2cmaster.h 定义了这样的函数原型：

i2cmaster.h defines the function prototype like this:

extern void i2c_init(void);

在汇编器文件中， i2cmaster.S ，该函数是：

And in the assembler file, i2cmaster.S, that function is:

.global i2c_init
.func i2c_init
i2c_init:
cbi SDA_DDR,SDA     ;release SDA
cbi SCL_DDR,SCL     ;release SCL
cbi SDA_OUT,SDA
cbi SCL_OUT,SCL
ret
.endfunc

链接看起来像一个没有脑子的 - 但我得到的参考错误。我注意到为 Main.cpp 生成的汇编代码如下：

The linking would seem like a no-brainer - but I get that reference error. I noticed the assembler code generated for Main.cpp comes out like this:

.global main
.type   main, @function
main:
rcall _Z8i2c_initv
.L2:
rjmp .L2
.size   main, .-main

我怀疑问题是 i2c_init 正在通过一些名称管理过程变得 _Z8i2c_initv 我不明白， _Z8i2c_initv 无法再匹配在 i2cmaster.o 对象文件中的未损坏的 i2c_init 符号。

I suspect the problem is that i2c_init is becoming _Z8i2c_initv through some name mangling process I don't understand, and that _Z8i2c_initv can no longer be matched with the non-mangled i2c_init symbol in the i2cmaster.o object file.

有没有人理解这个过程，以及如何在编译/汇编过程中抑制它，使这些模块可以相互通信？还是别的什么我可能做错了？

Does anyone understand the mangling process, and how to suppress it during compilation/assembly so that these modules can talk to each other? Or anything else I might be doing wrong?

推荐答案

确定，解决了。显然，符号调整是一个C ++的东西，并且i2c库没有设置为正确使用C ++。可以使用以下方法修复它：

OK, solved it. Apparently the symbol mangling is a C++ thing, and the i2c library isn't set up to work with C++ correctly. Was able to fix it by using the following:

extern "C" {
    #include "i2cmaster.h"
};
void main() { 
    i2c_init();
    while ( true ) {
    }
}

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