Re: string variables and literals

[Eric Lemings <eric dot b dot lemings at lmco dot com>]

sidster wrote:

> When you have code like:
> 
>    char* p = "some string";
> 
> 'p' is a pointer to a constant static string.  The memory location
> pointed to by 'p' should not be modifiable.

I'll try to clarify.  This is a string literal: "string literal".  This
is a pointer to an array of constant characters: const char* cs.  This
is a pointer to an array of non-constant characters: char* s.  Except
when initialized with a string literal?  C'mon.

p is NOT a pointer to a constant static string.  p is a pointer to an
array of non-constant characters.  You DON'T get a warning when it is
initialized and you DON'T get a warning when you pass it to a function
as a char* such as strcmp.  (Well, unless the warning is explictly
specified.)  But you do get a core dump.  That's not good behavior IMHO.

> The compiler doesn't warn about this but the user should be smart enough
> to realize s/he can't modify the character array pointed to by 'p'.

The compiler should at a minimum issue a warning: "assigning constant
literal to non-constant variable".  Personally, I would like to see it
initialize char* variables just as it does char[] variables.  The
semantics would be more consistent.

Also, I checked the standard.  Modification of variables declared with
type char* that are intialized with string literals is undefined.  So
technically, gcc is standardized in this respect.  But I think gcc
should ditch the exception that char* variables can be modified UNLESS
they are initialized with string literals.

Eric.