I appreciate your confidence, but you are wrong:

OpenSolaris/suncc, Jacques' program:

  $ cat immutable.c
  #include <stdio.h>

  int main()
  {
    char * s = "abc";
    *s = 'c';
    printf("%s\n", s);
    return 0;
  }

  $ cc -o immutable immutable.c 
  $ ./immutable 
  cbc

EDIT: I can't reply to you, so I have to take this route. I also think that this behavior is not desirable. However, I do not see the passage in the the standard that forbids writable strings. On the contrary, in Annex J writable string literals are explicitly allowed as an extension, and I don't see any indication that the presence of writable strings make an implementation non-conforming.

Perhaps you could point to the passage in the standard that requires string literals to be immutable (your words, not mine) or that requires a compiler to issue a warning if a string literal is modified.

If you still wonder why I'm arguing this: It is not for the sake of nitpicking, but to support kabdib's post.