Example
The first if statement may appear to check if the arguments are the same, but it will only succeed if they are different.

void foo( char *string1, char *string2)
{
if( strcmp(string1, string2) ) {
//the strings are the different
}

if( !strcmp(string1, string2) ) {
//the strings are the same
}
}

Solution
To avoid this misunderstanding a coding guideline may require that the if-statements be written as below.

void foo( char *string1, char *string2)
{
if(strcmp(string1, string2) != 0) {
//the strings are the different
}

if( strcmp(string1, string2) == 0) {
//the strings are the same
}
}