Verify type of string (e.g. literal, array, pointer) passed to a function [duplicate]

Answer 1

This does not work, sizeof(char *) returns the size of the pointer not the memory allocated or string size.

strlen(x) returns the size of a string by looking for the '\0'.

Answer 2

You can know it compile time, by simply changing your macro to:

#define STORE_STRING(X) store_string("" X, sizeof(X))

Usage:

char a[] = "abcd", *p;
STORE_STRING(a); // error
STORE_STRING(p); // error
STORE_STRING("abcd"); // ok

Answer 3

If you need/want a non-macro solution there is one template trick that can help. You can have a function signature that looks like this:

template<int len>
void store_string( char const (&str)[len] ) { store_string_internal( str,len); }

template<int len>
void store_string( char (&str)[len] ) { static_assert( false ); }

The first form accepts strings literals and calls the target function. The second form prevents non-const character arrays from being passed. And yeah, don't offer a char const* version.

This doesn't guarantee that the string is a string literal, but the one syntax needed to bypass it is extremely rare (I've never used it).

Otherwise the macro version from iammilind is nice.