string variables and literals

[Eric Lemings <elemings at uswest dot net>]

Dear readers,

Recently, I was quite surpised to discover the following behavior of GCC
which I think is a bug.

Suppose you have four strings defined as four different types:

    const char s1 [] = "array of null-terminated, const char";
    const char* s2 = "pointer to array of null-terminated, const char";
    char s3 [] = "array of null-terminated, non-const char";
    char* s4 = "pointer to array of null-terminated, non-const char";

Can s1 or s2 be modified?  Certainly not; they're declared as an array
and a pointer to const char, respectively.  Can s3 be modified?  Yes,
because it's declared as a non-const array of char.  The compiler
initializes it with a copy of the string literal from read-only memory
(where all string literals are stored).  Nothing wrong with that.

But what about s4?  Can it be modified?  It is not declared as a pointer
to const char.  But guess what?  That's exactly what it is.  The
compiler seemingly does not recognize the fact that it should be a
pointer to an array of __non-const__ char.  Just as s3 was initialized
with a copy of its string literal, shouldn't s4 be intialized with the
location of a copy of the string literal placed in some arbitrary part
of writable memory?

Thanks,
Eric.