Specifying an error handler

You can override this default behavior by using the librcheck version of mallopt() to specify what to do when a warning or a fatal condition is detected. The arguments to this function are:

cmd

The error handler to set; one of:

MALLOC_FATAL

Specify how to handle fatal errors.

MALLOC_WARN

Specify how to handle warnings.

The MALLOC_ACTION environment variable sets the handling for fatal errors and warnings to the same value.

value

An integer value that indicates how you want to handle the error:

Symbolic name	Value	Action
M_HANDLE_IGNORE	0	Ignore the error and continue
M_HANDLE_ABORT	1	Terminate execution with a call to abort()
M_HANDLE_EXIT	2	Exit immediately
M_HANDLE_CORE	3	Cause the program to dump a core file
M_HANDLE_STOP	4	Send a stop signal (SIGSTOP) to the current thread. Stopping the thread lets you attach to the process using a debugger. The program is stopped inside the error-handler function, and a backtrace from there should show you the exact location of the error.

If you call mallopt(), you can OR any of these handlers with M_HANDLE_DUMP, to cause a complete dump of the heap before the handler takes action.

If you use the environment variable, you must set it to one of the numeric values, not the corresponding M_HANDLE_* symbolic name.

Here's how you can cause a memory overlap error to abort your program:

mallopt(MALLOC_WARN, M_HANDLE_ABORT);

char *foo = malloc(1024);
strcat(foo, "firstsecond");
strncat(&foo[5], &foo[0], 6); /* warning generated and abort() called */