The mudflap run time checker was removed in GCC 4.9 and it is superseded by Address Sanitizer. The mudflap options remain, but do nothing. This page applies only to earlier versions of GCC. Mudflap Pointer Debugging It is enabled by passing -fmudflap to the compiler. For front-ends that support it (C and very simple C++ programs), it instruments all risky pointer/array dereferencing operations, so