Signal handlers allow C programs to respond to events outside of the normal control flow (see signal.h, etc.). This means that once a function, say fnc1, has returned, the memory on the stack that was used by fnc1 can end up being reused at any point in time. A signal, perhaps generated completely asynchronous to the program itself by a different process, causes a stack frame to be allocated (possibly on top of fnc1’s old stack frame) for use by the corresponding signal handler. This could happen at any time, even before fnc1’s caller gets a chance to use the pointer returned by fnc1.
Signal handlers allow C programs to respond to events outside of the normal control flow (see signal.h, etc.). This means that once a function, say fnc1, has returned, the memory on the stack that was used by fnc1 can end up being reused at any point in time. A signal, perhaps generated completely asynchronous to the program itself by a different process, causes a stack frame to be allocated (possibly on top of fnc1’s old stack frame) for use by the corresponding signal handler. This could happen at any time, even before fnc1’s caller gets a chance to use the pointer returned by fnc1.