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What is dereferencing null pointer in C?
A NULL pointer dereference is a sub type of an error causing a segmentation fault. It occurs when a program attempts to read or write to memory with a NULL pointer. Consequences. Running a program that contains a NULL pointer dereference generates an immediate segmentation fault error.
Can we dereference a null pointer?
The program can potentially dereference a null pointer, thereby raising a NullPointerException. Null pointer errors are usually the result of one or more programmer assumptions being violated. A null-pointer dereference takes place when a pointer with a value of NULL is used as though it pointed to a valid memory area.
Can you free a null pointer in C?
It is safe to free a null pointer. The C Standard specifies that free(NULL) has no effect: The free function causes the space pointed to by ptr to be deallocated, that is, made available for further allocation. If ptr is a null pointer, no action occurs.
What happens if you dereference NULL?
Dereferencing a null pointer always results in undefined behavior and can cause crashes. If the compiler finds a pointer dereference, it treats that pointer as nonnull. As a result, the optimizer may remove null equality checks for dereferenced pointers.
Can you dereference a NULL pointer explain it with suitable examples?
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions.
What happens if you dereference a freed pointer?
If two pointers point at the same address, and you free() one of them, the other one becomes invalid but it’s value doesn’t change. Neither does the value of the first; it’s just that dereferencing either of them just became an invalid thing to do.