are all serious errors, symptoms of a wild pointer or subscript.
Null pointer assignment is a message you might get when an MS-DOS
program finishes executing. Some such programs can arrange for a
small amount of memory to be available “where the NULL pointer
points to (so to speak).
If the program tries to write to that area, it will overwrite the
data put there by the compiler.
When the program is done, code generated by the compiler examines
that area. If that data has been changed, the compiler-generated
code complains with null pointer assignment.
This message carries only enough information to get you worried.
There’s no way to tell, just from a null pointer assignment message,
what part of your program is responsible for the error. Some
debuggers, and some compilers, can give you more help in finding the
Bus error: core dumped and Memory fault: core dumped are messages
you might see from a program running under UNIX. They’re more
programmer friendly. Both mean that a pointer or an array subscript
was wildly out of bounds. You can get these messages on a read or on
a write. They aren’t restricted to null pointer problems.
The core dumped part of the message is telling you about a file,
called core, that has just been written in your current directory.
This is a dump of everything on the stack and in the heap at the
time the program was running. With the help of a debugger, you can
use the core dump to find where the bad pointer was used.
That might not tell you why the pointer was bad, but it’s a step in
the right direction. If you don’t have write permission in the
current directory, you won’t get a core file, or the core dumped