Is casting a const char array to an integer in the header always safe?

Question

Ignoring how repulsive and hacky it is, is the following guaranteed to be safe? If not, why?

//.h
struct foo
{
 const static intptr_t KEY = (intptr_t) "VALUE";
};

//.cpp
void useFoo()
{
 const char * value = (const char *) foo::KEY;
 printf("%s",value);
}

As a poor man's way to initialize a const static string in the header. Until c++0x, you could only initialize integral types in the header. You could use #define, or you could initialize the string in the .cpp. I was wondering if this was another way to achieve the same result. — tgoodhart, Jun 29 '12 at 19:12

score 3 · Answer 1 · answered Jun 29 '12 at 18:59

3

Not only is the code not guaranteed to be safe, the code is ill-formed.

"VALUE" is of type char const[6], which cannot be converted to intptr_t via static_cast.

answered Jun 29 '12 at 18:59

James McNellis

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I used the wrong type of cast. I was trying to avoid the c-style cast if possible. The spirit of the question is to cast the address of the beginning of a character array literal to an integer in the header then recover it in the .cpp. – tgoodhart Jun 29 '12 at 19:04

score 2 · Answer 2 · answered Jun 29 '12 at 19:00

It is guaranteed not to compile. You cannot use static_cast to convert from pointer to an integral type or viceversa. If it was a reinterpret_cast it would be fragile to say the least as the compiler can do constant folding and the KEY might become non-unique.

Additionally, you should define the static member variable KEY in your application.

Is casting a const char array to an integer in the header always safe?

2 Answers2