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Warning C6319

  • Article

Use of the comma-operator in a tested expression causes the left argument to be ignored when it has no side-effects

Remarks

This warning indicates an ignored sub-expression in test context because of the comma-operator (,). The comma operator has left-to-right associativity. The result of the comma-operator is the last expression evaluated. If the left expression to comma-operator has no side effects, the compiler might omit code generation for the expression.

Code analysis name: IGNOREDBYCOMMA

Example

The following code generates this warning:

void f()
{
  int i;
  int x[10];

  for ( i = 0; x[i] != 0, x[i] < 42; i++)  // warning
  {
    // code
  }
}

To correct this warning, use the logical AND operator as shown in the following code:

void f()
{
  int i;
  int x[10];

  for ( i = 0; (x[i] != 0) && (x[i] < 42); i++)
  {
    // code
  }
}

See also