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From: weave@brahms.udel.edu (Ken Weaverling)
Newsgroups: comp.lang.c
Subject: Returning pointers to constant strings
Keywords: static constant string
Message-ID: <21139@brahms.udel.edu>
Date: 6 May 91 15:02:46 GMT
Distribution: na
Organization: University of Delaware
Lines: 51

I have scanned the FAQs and have also discussed this topic in a local group,
but would now like to get a few more opinions.

Question: Is there anything dangerous with returning pointers to literal
strings? Is there a portability issue to consider? Is it just bad practice?

Sample code:

char *phredd () {

   char *phrogg;

   phrogg = "Phredd Phrogg's Phantasy Philm";

   return phrogg;
}

 *Solutions* to this are many, such as returning a pointer to a static char
 array, making the literal a global, strdup()'ing it, or strcpy()'ing it
 to another place.  I am concerned with the mentioned issue though.

In the local newsgroup at Univ of Del, the consensus was that it would be
a bad idea, due to systems such as Mess/DOS that might use code overlays,
and the constant string might be stored in a code overlay that would not
always be resident.

I used gdb against a gcc compiled source to verify that the string was 
stored in the code segment just after a function (but not necessarily
the same function that it is used in). I know that it is not a good idea
to alter the string, but that also is not the issue.

Well, I referred to the *bible* for C, the Kernighan and Ritchie book on C,
second edition (for ANSI C).  It says on page 194, section A2.6 ...

A string literal, also called a string constant, is a sequence of characters
surrounded by double quotes, as in "...". A string has type "array of
characters" and storage class *static*.  Whether identical strings are
distinct is implementation-defined, and the behavior of a program that
attempts to alter a string literal is undefined.

.... and then the definition of static from section A4.1 ...

Static objects may be local to a block or external to all blocks, but in
either case, retain their values across exit from and reentry to functions
and blocks.

So, from above, I infer that there is nothing wrong with the code above.
Any comments? Is it still bad practice from a style standpoint? Thanks!

-- 
>>>---> Ken Weaverling  >>>---->  weave@brahms.udel.edu