"Very few people out there know that the volatile type qualifier exists"? Only if there are "very few" kernel programmers, embedded programmers, and others who have used C for anything low-level and/or multi-threaded. Otherwise, no. Sorry, but knowing about it doesn't make you special.
"Volatile" is the wrong fix, by the way. That's just depending on yet another non-required behavior. There is in fact no further reference to "str" between the function call and the reassignment at the start of the next iteration, so there's nothing for "volatile" to chew on. This particular version of this particular compiler just happens to add an extra pair of stack operations in this case, but it's not truly required to. A real fix would not only mark the variable as volatile but also add a reference after the function call. The same "(void)str;" type of statement that's often used to suppress "unused argument/variable" warnings should count as a reference to force correct behavior here.
"Volatile" is the wrong fix, by the way. That's just depending on yet another non-required behavior. There is in fact no further reference to "str" between the function call and the reassignment at the start of the next iteration, so there's nothing for "volatile" to chew on. This particular version of this particular compiler just happens to add an extra pair of stack operations in this case, but it's not truly required to. A real fix would not only mark the variable as volatile but also add a reference after the function call. The same "(void)str;" type of statement that's often used to suppress "unused argument/variable" warnings should count as a reference to force correct behavior here.