C6509

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The latest version of this topic can be found at C6509.

warning C6509: invalid annotation: 'return' cannot be referenced from a precondition

This warning indicates that the return keyword cannot be used in a precondition. The return keyword is used to terminate the execution of a function and return control to the calling function.

The following code generates this warning because return is used in a precondition:

#include <sal.h>  
  
int f (_In_reads_(return) char *pc)  
{  
    // code ...  
    return 1;  
}  

To correct this warning, use the following code:

#include <sal.h>  
  
int f (_In_reads_(i) char *pc, int i)  
{  
    // code ...  
    return 1;  
}