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Compiler Warning (level 1) C4288

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nonstandard extension used : 'var' : loop control variable declared in the for-loop is used outside the for-loop scope; it conflicts with the declaration in the outer scope

When compiling with /Ze and /Zc:forscope-, a variable declared in a for loop was used after the for-loop scope. A Microsoft extension to the C++ language allows this variable to remain in scope, and C4288 reminds you that the first declaration of the variable is not used.

See /Zc:forScope for information about how to specify the Microsoft extension in for loops with /Ze.

The following sample generates C4288:

// C4288.cpp
// compile with: /W1 /c /Zc:forScope-
int main() {
   int i = 0;    // not used in this program
   for (int i = 0 ; ; ) ;
   i++;   // C4288 using for-loop declaration of i
}