POSIX-style error handling provides the most basic form of error handling possible, capable of being leveraged on almost any system, in almost any program. Written with standard C in mind, POSIX-style error handling takes the following form:
if (foo() != 0) {
std::cout << errno << '\n';
}
Generally, each function called either returns 0 on success or -1 on failure, and stores the error code into a global (non-thread safe) implementation-defined macro, called errno. The reason 0 is used for success is that on most CPUs, comparing a variable to 0 is faster than comparing a variable to any other value, and the success case is the expected case. The following example demonstrates how this pattern is used:
#include <cstring>
#include <iostream>
int myfunc(int val)
{
if (val == 42) {
errno = EINVAL;
return...
