Nested functions are convenient, but when you take the address of a nested function that refers to surrounding variables, GCC puts a small trampoline function o

Nested functions are convenient, but when you take the address of a nested function that refers to surrounding variables, GCC puts a small trampoline function on the stack. To do this it has to disable the no-execute flag on the stack, which makes it significantly easier to exploit stack overflow vulnerabilities in your program. Since the implementation is somewhat complex and system-specific, depends on memory that is both writeable and executable, and requires disabling security features on modern OSes, I doubt GCC style nested functions will make it into the standard.