nullptr | (since C23) |
The keyword nullptr denotes a predefined null pointer constant. It is a non-lvalue of type nullptr_t. nullptr can be converted to a pointer types or bool, where the result is the null pointer value of that type or false respectively.
Demonstrates that a copy of nullptr can also be used as a null pointer constant.
#include <stddef.h>
#include <stdio.h>
void g(int*)
{
puts("Function g called");
}
#define DETECT_NULL_POINTER_CONSTANT(e) \
_Generic(e, \
void* : puts("void*"), \
nullptr_t : puts("nullptr_t"), \
default : puts("integer") \
)
int main()
{
g(nullptr); // Fine
g(NULL); // Fine
g(0); // Fine
puts("----------------");
auto cloned_nullptr = nullptr;
auto cloned_NULL = NULL;
auto cloned_zero = 0;
g(cloned_nullptr); // Fine
// g(cloned_NULL); // ERROR
// g(cloned_zero); // ERROR
puts("----------------");
DETECT_NULL_POINTER_CONSTANT(((void*)0));
DETECT_NULL_POINTER_CONSTANT(0);
DETECT_NULL_POINTER_CONSTANT(nullptr);
DETECT_NULL_POINTER_CONSTANT(NULL); // implementation-defined
}Possible output:
Function g called Function g called Function g called ---------------- Function g called ---------------- void* integer nullptr_t void*
| implementation-defined null pointer constant (macro constant) |
|
|
(C23) | the type of the predefined null pointer constant nullptr (typedef) |
C++ documentation for nullptr |
|
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