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Is it safe to assume that NULL always translates to false in C?
void *somePtr = NULL; if (!somePtr) { /* This will always be executed? */ } Or should an explicit check against the value of NULL be made?
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The value null represents the intentional absence of any object value. It is one of JavaScript's primitive values and is treated as falsy for boolean operations.
The way you typically represent a “missing” or “invalid” value in C# is to use the “null” value of the type. Every reference type has a “null” value; that is, the reference that does not actually refer to anything.
Yes. NULL evaluates to false, since C considers any non-zero value true and any zero value false.
The null pointer constant is always 0. The NULL macro may be defined by the implementation as a naked 0 , or a cast expression like (void *) 0 , or some other zero-valued integer expression (hence the "implementation defined" language in the standard). The null pointer value may be something other than 0.
Yes. NULL evaluates to false, since C considers any non-zero value true and any zero value false. NULL is essentially the zero address and is treated as such in comparisons, and I believe would be promoted to an int for the boolean check. I would expect that your code is readable to anyone familiar with C although I would probably make the check explicit.
In C and C++ programming, two null pointers are guaranteed to compare equal; ANSI C guarantees that any null pointer will be equal to 0 in a comparison with an integer type; furthermore the macro NULL is defined as a null pointer constant, that is value 0 (either as an integer type or converted to a pointer to void), so a null pointer will compare equal to NULL.
Ref: http://en.wikipedia.org/wiki/Null_pointer#Null_pointer
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