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Date: 5 Feb 93 14:10:54 GMT
From: theory.TC.Cornell.EDU!lijewski@tcgould.tn.cornell.edu  (Mike Lijewski)
Subject: Re: question on constant arrays
Message-ID: <1993Feb5.141054.29026@tc.cornell.edu>
List-Id: <comp.lang.ada>

In article <EMERY.93Feb4205855@dr_no.mitre.org> emery@dr_no.mitre.org (David Em
ery) writes:
>The exact Ada analog to the C record is as follows:
>	type strptr is access string;
>	type mytype is record
>		name : strptr;
>		T : integer;
>	end record;
>
>	type foo_array is array (natural range <>) of strptr;
>	foo : foo_array(1..2) := (new string'("Hi"), 1), 
>				  new string'("There"),2));
>
>In the C example, the compiler statically allocates space for the two
>string literals, and returns their address.  In the Ada case, you have
>to explictly allocate storage for the two strings, and use the
>access value.  
>
>Remember that in C, all strings are passed by the address of their
>first element.  This is not the way that Ada handles strings.  
>
>				dave
>p.s.  I suspect that you'll be in deep trouble with your C array of
>struct if you try to use any of the standard C techniques to iterate
>over the characters in the Name field.  Does C guarantee that string
>literals like "Hi" are null terminated?

C does guarantee that string literals are null terminated.  The one
"oddity" allowed by ANSI C is where one initializes a fixed size character
array, which is just large enough to hold the characters in the string
literal excluding the null, with a literal string. That is,

  char word[2] = "Hi";  /* word is not null terminated */

as contrasted to letting the compiler figure out the size of the array:

  char word[] = "Hi";   /* word is null terminated */

Why ANSI allowed this I don't know.  C++ disallows this special case.


-- 
Mike Lijewski  (H)301-982-5461 (W) 301-286-6115
Goddard Space Flight Center
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