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分享apue例子编译的问题
按照网上的方法编译出了libapue.a,但还是出现链接错误
$ gcc fig1.3.cpp -lapue
/tmp/ccswK9BA.o: In function `main':
fig1.3.cpp:(.text+0x20): undefined reference to `err_quit(char const*, ...)'
fig1.3.cpp:(.text+0x60): undefined reference to `err_sys(char const*, ...)'
collect2: error: ld returned 1 exit status
对libapue.a 使用 nm 查看结果，里面应该有这两个函数的哇，请问是什么原因导致链接错误的，怎么解决
error.o:
U abort
0000000000000413 t err_doit
0000000000000209 T err_dump
000000000000015a T err_exit
00000000000002b5 T err_msg
U __errno_location
0000000000000360 T err_quit
0000000000000000 T err_ret
00000000000000a9 T err_sys
$ gcc fig1.3.cpp -lapue
/tmp/ccswK9BA.o: In function `main':
fig1.3.cpp:(.text+0x20): undefined reference to `err_quit(char const*, ...)'
fig1.3.cpp:(.text+0x60): undefined reference to `err_sys(char const*, ...)'
collect2: error: ld returned 1 exit status
对libapue.a 使用 nm 查看结果，里面应该有这两个函数的哇，请问是什么原因导致链接错误的，怎么解决
error.o:
U abort
0000000000000413 t err_doit
0000000000000209 T err_dump
000000000000015a T err_exit
00000000000002b5 T err_msg
U __errno_location
0000000000000360 T err_quit
0000000000000000 T err_ret
00000000000000a9 T err_sys
...全文
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小笨和漂向北方 2014-07-21
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I haven't write make file for C++ using gcc for a while. I am not sure if gcc could decide using g++ by checking the suffix of the file.
Also, does APUE offer the makefile for compiling libapue.a? If so, there won't be any "name mangling" in there.
nm has proved that.
I think you should try to add -L/path2yourlib first. And I don't see -I path for include file as well. don't know why compiler didn't complain at the first place... [/quote]
我试了一下，确实调用的是g++。
$ cat ./main.cpp
int foo();
int main()
{
foo();
}
小笨和漂向北方 2014-07-21
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Thanks! You are right on the issue here.
just a side note here that using gcc (4.4.7) for cpp will have problem on linking process, certain c++ libraries will not be included. For my case libstdc++ was missing. You will have to explicitly append it to the make file.
So, calling g++ directly is the best choice. Anyway, this is not the topic of this post...
小笨和漂向北方 2014-07-20
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I haven't write make file for C++ using gcc for a while. I am not sure if gcc could decide using g++ by checking the suffix of the file.
Also, does APUE offer the makefile for compiling libapue.a? If so, there won't be any "name mangling" in there.
nm has proved that.
I think you should try to add -L/path2yourlib first. And I don't see -I path for include file as well. don't know why compiler didn't complain at the first place...
colddown 2014-07-20
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因为你的文件后缀是cpp，gcc当作C++文件并自动调用g++去编译，由于C++ name mangle 机制，函数名被修改了。你可以用先把cpp文件编译成.o文件（用-c），再用nm看看就能发现函数名被修改了。具体可以google C++ mangle。
简单的解决方法就是把文件名从.cpp改成.c。
另一种方法就是用extern C防止mangle。
colddown 2014-07-20
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I haven't write make file for C++ using gcc for a while. I am not sure if gcc could decide using g++ by checking the suffix of the file.
Also, does APUE offer the makefile for compiling libapue.a? If so, there won't be any "name mangling" in there.
nm has proved that.
I think you should try to add -L/path2yourlib first. And I don't see -I path for include file as well. don't know why compiler didn't complain at the first place... [/quote]
我试了一下，确实调用的是g++。
$ cat ./main.cpp
int foo();
int main()
{
foo();
}
