undifined reference for template

SybaseLU

a.h

1. template<class T>
   
2. class AList
   
3. {
   
4. public:
   
5.         AList() {}
   
6.         ~AList() {}
   
7. 
   
8.         void display(T value); /* if implemented the routine as inline function, then that's ok */
   
9. };

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a.cpp

1. #include "a.h"
   
2. 
   
3. template<class T>
   
4. void AList<T>::display(T value)
   
5. {
   
6.         printf("value:%d\n", value);
   
7. }

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main.cpp

1. #include <stdio.h>
   
2. #include <stdlib.h>
   
3. #include "a.h"
   
4. 
   
5. typedef AList<int> iA;
   
6. iA x;
   
7. 
   
8. int main()
   
9. {
   
10.         x.display(10);
    
11.         
    
12.         exit(0);
    
13. }

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complied

1. $ g++ -c a.cpp -o a.o
   
2. $ g++ -c main.cpp -o main.o
   
3. $ g++ -o bin main.o a.o
   
4. $ main.o(.text+0x1b): In function `main':
   
5. : undefined reference to `AList<int>::display(int)'
   
6. collect2: ld returned 1 exit status
   
7. [george@ahapvr LuYanJun]$

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[ 本帖最后由 SybaseLU 于 2007-8-7 09:21 编辑 ]

lenovo

一般情况下，模板实现要放在.h文件里的。

SybaseLU

Definitely, I try putting implementation of those functions in the header, everything goes well and work out nice. It's seem that only god know why.

lenovo

原帖由 SybaseLU 于 2007-8-7 09:45 发表
Definitely, I try putting implementation of those functions in the header, everything goes well and work out nice. It's seem that only god know why.

实现其实可以和声明分开的，
如果你想知道怎么做，
参考《C++ Templates: The Complete Guide》。

xujg

编译main.cpp的时候
编译器不知道void display(int value)的定义
想让链接器去找
但是链接器没找到

SybaseLU

Ok, let's go ahead. as for *.cpp project you should need the extern "C" only if you are calling a  C function , vice versa,  you should do the same for  *.c project . for instance

b.cpp

1. 
   
2. #include "a.h"
   
3. 
   
4. typedef AList<int> iA;
   
5. iA x;
   
6. 
   
7. #ifdef __cplusplus
   
8. extern "C" {
   
9. #endif
   
10. 
    
11. void OutputInfo()
    
12. {
    
13.         x.display(10);
    
14. }
    
15. 
    
16. #ifdef __cplusplus
    
17. }
    
18. #endif
    

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main.c

1. 
   
2. #include <stdio.h>
   
3. #include <stdlib.h>
   
4. 
   
5. extern  void OutputInfo();
   
6. 
   
7. int main()
   
8. {
   
9.         OutputInfo();
   
10.         exit(0);
    
11. }
    

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The result of compilation

1. 
   
2. $ gcc -c b.cpp -o b.o
   
3. $ gcc -c main.c -o main.o
   
4. $ gcc -o bin main.o b.o
   
5. b.o(.eh_frame+0x11): undefined reference to `__gxx_personality_v0'
   
6. collect2: ld returned 1 exit status
   
7. $
   
8. 
   

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I mean that you need extern "C" only if you are calling a fcuntion which be implemented within *.C/.cpp/.cc

[ 本帖最后由 SybaseLU 于 2007-8-7 11:45 编辑 ]

lenovo

原帖由 SybaseLU 于 2007-8-7 11:41 发表
Ok, let's go ahead. as for *.cpp project you should need the extern "C" only if you are calling a  C function , vice versa,  you should do the same for  *.c project . for instance

b.cpp

#in ...

你觉得c程序里能出现类，对象，模板这些东西吗？

SybaseLU

1 如果想在*.c中调用函数，而这些函数在*.cpp/.C/.cc中实现的呢？ 使用gcc。
2 在*.cpp/.C/.cc中使用函数，这些函数在*.c中实现的，同样需要extern "C", 使用g++
3 交叉编译

1. 
   
2. $ arm-elf-gcc -c b.cpp -o b.o
   
3. $ arm-elf-gcc -c main.c -o main.o
   
4. $ arm-elf-gcc -o bin main.o b.o
   
5. $
   

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为什么用arm-elf-gcc反而编译成功了，用gcc反而不行【BTW, the cross compilier was deprived from Sigma-design 】