Can I use if (pointer) instead of if (pointer != NULL)?

c++ pointers if-statement null null-pointer
danijar picture danijar · Jul 21, 2013 · Viewed 98.8k times · Source

Is it safe to check a pointer to not being NULL by writing simply if(pointer) or do I have to use if(pointer != NULL)?

Answer

Joni picture Joni · Jul 21, 2013

You can; the null pointer is implicitly converted into boolean false while non-null pointers are converted into true. From the C++11 standard, section on Boolean Conversions:

A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true . A prvalue of type std::nullptr_t can be converted to a prvalue of type bool ; the resulting value is false .

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