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Compiler Warning (level 1) C4547


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The latest version of this topic can be found at Compiler Warning (level 1) C4547.

operator' : operator before comma has no effect; expected operator with side-effect

The compiler detected an ill-formed comma expression.

This warning is off by default. For more information, see Compiler Warnings That Are Off by Default.

The following sample generates C4547:

// C4547.cpp  
// compile with: /W1  
#pragma warning (default : 4547)  
int i = 0;  
int j = 1;  
int main() {  
   int l = (i != i,0);   // C4547  
   // try the following line instead  
   // int l = (i != i);  
   // or  
   // int l = ((void)(i != i),0);