-qignerrno

In z/OS® XL C/C++, the -qignerrno option allows the compiler to perform optimizations as if system calls would not modify errno. The __IGNERRNO__ macro is defined to 1 when the -qignerrno option is in effect.

In Open XL C/C++ for z/OS, the -fno-math-errno option provides the same function as -qignerrno. However, -fno-math-errno does not predefine __IGNERRNO__.