Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!motcid!henley
From: henley@motcid.UUCP (Aaron Henley)
Newsgroups: comp.lang.c
Subject: Re: free (NULL);
Keywords: free
Message-ID: <2855@mica6.UUCP>
Date: 9 May 90 15:04:59 GMT
References: <1194@wet.UUCP>
Reply-To: motcid!henley@uunet.uu.net
Organization: Motorola Inc., Cellular Infrastructure Div., Arlington Heights, IL
Lines: 42

noah@wet.UUCP (Noah Spurrier) writes:


>char *squirl()
>{
>  static char *test = NULL;

>  free (test);

>  test = (char *) malloc (100);

>  return (test);
>}

>This function is run many times so iI do not want to protect it with an if
>because the if would only be useful for the first time it is run, after that
>it just eats up run time.

>   if (test != NULL)
>      free (test);

>Will angry things happen if I try to free(NULL) ?

ANSI C may specify that free(NULL) should work, but for those
people currently not using an ANSI C compiler the following
will also work:

	static char *test = (char *) malloc (100);

This obviously wastes time during the first execution, but should work
across all K&R C libraries and ANSI C libraries.

BTW:  If the ANSI C library supports this, does this mean that
the "if (test != NULL)" is done by the library which now means that
you'll always use up your run time with this test even if you
know the test isn't needed?

-- 
   ___________________________________________________________________
  /  Aaron Henley, Motorola Inc.      DISCLAIMER: std.disclaimer     /
 / Cellular Infrastructure Division   UUCP: ...!uunet!motcid!henley /
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