如何从链接器错误到源代码行? [英] How to go from linker error to line of code in the sources?
问题描述
链接器产生这种输出
/var/tmp/ccITB4j2.o: In function `main':
/var/tmp/ccITB4j2.o(.text+0x4): undefined reference to `myFunction(void)'
我如何找到对应于.text + 0x4的指令所在的源代码行?
How can I find out the line of source code corresponding to the instruction at .text+0x4 where the function is actually invoked?
推荐答案
首先,您的问题的另一个答案是错误的:在Linux上,您可以从链接器获取文件和行号:
First, the other answer to your question is wrong: on Linux you do get file and line number from the linker:
$ cat foo.cc
extern int myFunction(void);
int main()
{
return myFunction();
}
$ g++ -g foo.cc
/tmp/cc3twlhL.o: In function `main':
/tmp/foo.cc:5: undefined reference to `myFunction()'
collect2: ld returned 1 exit status
c $ c> gcc(Ubuntu / Linaro 4.6.3-1ubuntu5)4.6.3 和链接器 GNU ld(GNU Binutils for Ubuntu)2.22
但是对于更旧版本的GCC和ld也是如此。
Above output is from gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
and linker GNU ld (GNU Binutils for Ubuntu) 2.22
, but this has been true for much older versions of GCC and ld as well.
无法获取文件/行的原因必须是
The reason you are not getting the file/line must be that
- 您未使用
-g
标志或 - 您拥有真的旧
ld
或 - 您已配置
ld
不支持调试(我不确定这是否可能)。
- you didn't use
-g
flag, or - you have a really old
ld
, or - you have configured your
ld
without support for debugging (I am not sure this is even possible).
ld
拒绝告诉您文件和行,不是所有都丢失。您可以将源代码编译成对象,然后使用 objdump -rdS foo.o
获得相同的信息:
However, even if your ld
is refusing to tell you the file and line, not all is lost. You can compile your source into object, then use objdump -rdS foo.o
to obtain the same info:
g++ -g -c foo.cc
objdump -rdS foo.o
Disassembly of section .text:
0000000000000000 <main>:
extern int myFunction(void);
int main()
{
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
return myFunction();
4: e8 00 00 00 00 callq 9 <main+0x9>
5: R_X86_64_PC32 _Z10myFunctionv-0x4
}
9: 5d pop %rbp
a: c3 retq
在上面的输出中,您可以清楚地看到哪条源代码行引用了 _Z10myFunctionv
(这是 C ++
myFunction(void)
的错误名称将在对象文件中发出。
In above output, you can clearly see which source line caused reference to _Z10myFunctionv
(which is the C++
mangled name for myFunction(void)
) to be emitted in the object file.
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