inline陷阱问题

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在规范c++编程时遇到的，即类的文件定义

常规的对类的使用，在class.h对类进行生命，对于成员函数在class.cpp中定义，如下实现

main.cpp
#include<iostream>

#include "person.h"

using namespace std;


int main()
{
 person p;
 p.setage(12);
 cout<<p.backage()<<endl;

 return 0;
}

person.h
#ifndef _PERSON_H_
#define _PERSON_H_
class person
{
public:
  void setage(int n);
  int backage();
private:
 int age;
};
#endif

person.cpp
#include "person.h"
void person::setage(int n)
{
 age=n;
}
int person::backage()
{
 return age;
}

class person
{
public:
 inline void setage(int n);
 inline int backage();
private:
 int age;
};

t.c文件
inline void f()
{
 int a;
 a++;
}

int main()
{
 f();
 return 0;
}

f:
 pushq	%rbp
 movq	%rsp, %rbp
 addl	$1, -4(%rbp)
 popq	%rbp
 ret
main:
 pushq	%rbp
 movq	%rsp, %rbp
 movl	$0, %eax
 call	f
 movl	$0, %eax
 popq	%rbp
 ret

#include<stdio.h>
inline int f(int a)
{
 a++;
 printf("a=%d\n",a);
 return a;
}
int main()
{
 int b=0;
 b=f(b);
 printf("b=%d\n",b);
 return 0;
}

main:
 subq	$8, %rsp
 movl	$1, %edx
 movl	$.LC0, %esi
 movl	$1, %edi
 xorl	%eax, %eax
 call	__printf_chk

 movl	$1, %edx
 movl	$.LC1, %esi
 movl	$1, %edi
 xorl	%eax, %eax
 call	__printf_chk  

 xorl	%eax, %eax
 addq	$8, %rsp
 ret

inline function shall be defined in every translation unit in which it is used and shall have exactly the same definition in every case.
并且有人对此做了研究，下面是对话

 >     File1.cc:
 >     ----------------snip here----------------
 >     inline int foo (int x) { return x; }
 >
 >     int bar() { return foo(2); }
 >     ----------------snip here----------------
 >
 >     File2.cc:
 >     ----------------snip here----------------
 >     inline int foo (int);
 >
 >     int main() { return foo(1); }
 >     ----------------snip here----------------
 >
 >     If I compile this using "g++ File1.cc File2.cc" I get a working
 program
 >     that returns 1. If I compile it with "-O" enabled, I get a linker
 error:
 >
 >       Unresolved text symbol "foo(int)" -- 1st referenced by
 /var/tmp//cckhU7pa.o.
 >
 >     Without optimization the function "foo" in the first file isn't
 inlined.
 >     But because it's used by "bar" it is put in the object file. With
 optimization
 >     the function is inlined and doesn't appear explicitly in the object
 file of
 >     the first file. Therefore, the linker error.
 >
 >     In essence: The compiler does not need to put inline functions in the
 object
 >     file. The compiler can just optimize them away. And because of that we
 have
 >     paragraph 7.1.2.4.

inline function shall be defined in every translation unit in which it is used and shall have exactly the same definition in every case.
并且有人对此做了研究，下面是对话

到此就明白了，在我上面的那个c++类中，如果main要调用内联的成员函数，那么在main所在的这个文件里必须要有内联函数的定义

所以修改为

main.cpp
#include<iostream>

#include "person.h"
#include "person.cpp"
using namespace std;


int main()
{
 person p;
 p.setage(12);
 cout<<p.backage()<<endl;

 return 0;
}

inline陷阱问题

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原文地址：http://blog.csdn.net/u010442328/article/details/47295409