I have a function that returns an error string. The value is actually the address of an internal data member (I don't want to allocate memory and copy the string - I don't trust that the "user" would free it), and consequently, I don't want anyone to screw around with its contents. So how do I declare the return value so that the contents of the string are constant as opposed to the pointer's value being constant? (I hope that made sense)

const char *foo()

(const char) *foo()

<edit>
typedef const char c_char
typedef c_char * c_string

That seems a bit klunky though...
</edit>

I hate having to ask (it seems such a fundamental thing) but I rarely use constant strings other than literals in my code.

Ugh... I should look more closely at my reference material.

From the "C/C++ Programmer's Reference (Second Edition)"
As usual, I was trying to make things too complicated.

NOTE: That only applies to C++ compilers. C++ is much more strict with the const qualifier than C is.

String literals in C or C++ are constant regardless of whether you assign them to a const variable or not. For example:

char *foo = "some error string";

Results in foo pointing to a constant string (the results are undefined if you try to modify the string; if you're using gcc, the program will crash). So as long as you return a string constant, the user of the function could not modify the error string without crashing their program.

Alex