NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/comp/unix/aix/13148

Text File | 1993-01-08 | 2.6 KB | 57 lines

Newsgroups: comp.unix.aix
Path: sparky!uunet!zaphod.mps.ohio-state.edu!cs.utexas.edu!geraldo.cc.utexas.edu!portal.austin.ibm.com!awdprime.austin.ibm.com!codesmith.austin.ibm.com!dcm
From: [e-mail] (Craig Miller - [e-mail])
Subject: Re: malloc(0) fails on AIX and nowhere else I could find ...
Sender: [e-mail] (News id)
Message-ID: <[e-mail]>
Date: Fri, 8 Jan 1993 19:28:57 GMT
References: <[e-mail]> <[e-mail]> <[e-mail]>
Organization: IBM AWD, Austin
Lines: 45

In article <[e-mail]> [e-mail] writes:
>...
>Say you're implementing a strings package and your string descriptor
>looks like struct string { int count; char *ptr }; Now when you assign
>to a string you want to malloc (or realloc) the right # of bytes and
>assign the return value from malloc to the ptr.  But with AIX (and
>many other SysV-based systems), you have to explicitly test in case
>the string you want to assign is zero length.

those who support malloc(0):    ptr = malloc(length);
those who don't:        ptr = (length == 0) ? NULL : malloc(length);

Right?  And the second case *always* works, regardless of whether the
local implementation of malloc supports malloc(0) or not.  Right?

So the second case is portable.  Right?

Five or six years ago, when I was developing applications, I wrote all
my apps the second way.  I realized that malloc(0) had basically been
undefined since day one.  Wouldn't it be more portable and easier to
simply design your application this way instead of complaining each time
you try to port your application to a new box?

>Saying you shouldn't be able to malloc() zero bytes is like saying you
>shouldn't be able to have a zero-length file, or an empty record in a
>file, or you shouldn't be able to multiply something by zero.

I disagree.  Saying you shouldn't be able to malloc() zero bytes is
similiar to saying you can't strcpy() NULL: the behavior is undefined.
They've always been undefined!  Why depend on some implementation-specific
behavior when C gives you the opportunity to do otherwise?

>To be fair, AIX isn't unique in this regard -- most SysV based systems
>work this way.  Like most of the features unique to SysV, this one is
>a botch.

To most BSD users, SysV is a botch! (I used BSD in college and was a
BSD bigot until I was forced to use SysV...  And forced to realize
what it took to write BSD/SysV portably programs)

    Craig
--
Craig Miller, software mechanic:  AIXV3 Change Team (Level3 support)
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