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From: perry@inteloa.intel.com (Perry The Cynic)
Newsgroups: comp.sys.ibm.pc
Subject: Re: MSC 4.0 and the Twilight Zone
Message-ID: <635@omepd>
Date: Mon, 4-May-87 18:33:50 EDT
Article-I.D.: omepd.635
Posted: Mon May  4 18:33:50 1987
Date-Received: Wed, 6-May-87 01:06:47 EDT
References: <2454@uw-june.UUCP>
Sender: news@omepd
Reply-To: perry@inteloa.intel.com (Perry The Cynic)
Distribution: na
Organization: Intel Corp., Hillsboro
Lines: 15
Summary: *strdup*-allocated strings canNOT be extended

In article <2454@uw-june.UUCP> roper@uw-june.UUCP (Michael Roper) writes:
>Can anyone please explain the behavior of the following few lines of code?
> [...showing a sample program containing the following lines of code:]
> s = strdup (argv[1]);
> strcat (s, ".U");
*strdup* allocates exactly enough memory to hold a copy of its argument
plus the zero byte terminator. Your *strcat* tries to write *beyond* this
area, effectively corrupting the heap area. The next allocation (strdup)
that you (dynamically) make clobbers the byte holding the "U" (the "."
replaces the zero byte and is `safe' :-).
  -- perry
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