Compiler Warning (level 4) C4210

 

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The latest version of this topic can be found at Compiler Warning (level 4) C4210.

nonstandard extension used : function given file scope

With the default Microsoft extensions (/Ze), function declarations have file scope.

// C4210.c  
// compile with: /W4 /c  
void func1()  
{  
   extern int func2( double );   // C4210 expected  
}  
  
int main()  
{  
   func2( 4 );   //  /Ze passes 4 as type double  
}                //  /Za passes 4 as type int  

This extension can prevent your code from being portable to other compilers.

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