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From: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Newsgroups: alt.msdos.programmer,comp.sys.ibm.pc
Subject: Re: Calling C functions from assembly
Message-ID: <4140@lindy.Stanford.EDU>
Date: 2 Aug 89 19:04:28 GMT
References: <12324@s.ms.uky.edu> <663@megatek.UUCP>
Sender: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Reply-To: ralerche@lindy.Stanford.EDU (Robert A. Lerche)
Organization: Research Libraries Group
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A thing to watch out for when interfacing C and Assembler... the direction
flag!

Microsoft C's "memcpy" _assumes_ the direction flag is clear (i.e., it
doesn't do its own CLD before a REP MOVS).  Be sure to clear the direction
flag before calling a C routine and clear it if you set it in your own
assembler routine -- otherwise havoc can ensue.