Runtime-constraint violations

Somewhat hidden in Annex K, C11 introduces a new term into the C standard, namely runtime-constraint violations. They offer an important change of concept for the functions that are defined in that annex: if such a function is e.g called with invalid parameters, a specific function (called runtime-constraint handler) is called, that could e.g abort the program, or just issue an error message. This is in sharp contrast to the runtime error handling in the rest of the C standard, where the behavior under such errors is mostly undefined (anything may happen then) or sometimes reported to implementation defined behavior (and thus poorly portable and predictable).

Annex K, obscurely coined “Bounds checking interfaces“, introduces some typedef and a series of replacement functions for many C library functions. The function names in this series are usually derived from the name of the function they replace and by adding the suffix _s to the function name, e.g the function qsort gets a “secure” twin interface called qsort_s, as we have seen in an earlier post.