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From: rmeyers@tle.dec.com.UUCP
Newsgroups: comp.sys.amiga
Subject: Re: Leo's ANSI C flame
Message-ID: <8807010927.AA11844@decwrl.dec.com>
Date: 1 Jul 88 09:27:09 GMT
Organization: Digital Equipment Corporation
Lines: 54


Tim Olson, tim@delirun.amd.com, took exception to my statement that
Kernighan and Ritchie never guaranteed the string constants were
modifiable:

|Well, K&R say that string constants are type "array of characters", and
|there is no such read-only restriction on this type.

I don't find this argument too convincing.  K&R also says that the
constant 1L has type "long int."  That type doesn't have any read-only
restrictions.  Does that really imply anything?

|In fact, they went out of their way to allow such manipulation, because
|they declared that *all* string constants, even when written identically,
|are distinct.

That K&R promised that all string constants were distinct is not
sufficient to state that K&R promises that string constants can
be written.  It is fairly trivial to write a compiler that write
locks string constants but makes them all distinct.

K&R never promise that string constants can be modified.  They never
state it, and they show no examples of it.  Personally, I find it
interesting that they always refer to the beasts as "string constants"
and the ANSI standard always refers to them as "string literals,"
a term less prejudicial about whether the string can be modified.
I think that the ANSI standard is more willing to discuss the sordid
uses of string "constants" than K&R.

The real problem is here that K&R is not a formal definition of C.  It
leaves a number of questions unanswered (the reason that the ANSI C
committee exists is not to either improve or "screw up" the language:
it exists simply to provide a formal definition for it).  For example,
does K&R allow you to convert a pointer to a function to a pointer
to an int?  Does the existence of that capability imply that you
can not have execute only code because you care free to write memory
through int pointers?

|Leo's argument that a compiler that optimized and assigned 16 to x for
| 
|	x = strlen("constant string");
| 
|would break if he modified the string at runtime is incorrect, because
|there is no way to get a legal pointer to the string in the above
|expression ("constant string" is distinct from any other string
|constant).

Good point!
 
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Randy Meyers, not representing Digital Equipment Corporation
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