// --------inline.h--------
struct X {
static inline void foo ();
};
#ifdef YES
inline void X::foo () { cout << "YES\n"; }
#else
inline void X::foo () { cout << "NO\n"; }
#endif
// --------file1.cpp--------
#define YES // <----
#include"inline.h"
void fun1 ()
{
X::foo();
}
// --------file2.cpp--------
#include"inline.h"
void fun2 ()
{
X::foo();
}
如果我们调用fun1()和fun2(),那么它们将分别打印YES和NO,这意味着它们是引用相同X :: foo()的不同函数体.
无论是否应该编码,我的问题是：
这是一个明确定义还是未定义的行为？
解决方法
参考：
C 03标准：
7.1.2函数说明符[dcl.fct.spec]
第4段：
An inline function shall be defined in every translation unit in which it is used and shall have exactly the same definition in every case (3.2). [Note: a call to the inline function may be encountered before its definition appears in the translation unit. ] If a function with external linkage is declared inline in one translation unit,it shall be declared inline in all translation units in which it appears; no diagnostic is required. An
inline function with external linkage shall have the same address in all translation units. A static local variable in an extern inline function always refers to the same object. A string literal in an extern inline function is the same object in different translation units.
注意：3.2指一定义规则,其中规定：
3.2一个定义规则[basic.def.odr]
第1段：
No translation unit shall contain more than one definition of any variable,function,class type,enumeration type or template.
