Xref: news2.mv.net comp.os.msdos.djgpp:6703
From: alaric AT abwillms DOT demon DOT co DOT uk (Alaric B. Williams)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: return type of malloc?
Date: Tue, 30 Jul 1996 17:12:02 GMT
Lines: 51
Message-ID: <838746612.16082.9@abwillms.demon.co.uk>
References: <4thu6e$nsr AT oravannahka DOT Helsinki DOT FI>
NNTP-Posting-Host: abwillms.demon.co.uk
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

reynders AT cc DOT Helsinki DOT FI (Joonas W N Reynders) wrote:


>	What type is the pointer malloc returns? Is it a selector:offset
>pair, just a 32bit offset or what? The reason I need to know this is
>that I've got a few routines made with MASM which copy information from
>a mallocated buffer to SVGA buffer.

Wow. That'll need total rewriting for DJGPP :-)

All DJGPP pointers are 32-bit offsets into The Segment.

DS, SS, ES, and CS all point to The Segment, or aliases thereof.

Thus we can ignore segments alltogether, and just use [xyz] in
assembler... or in AT&T syntax, just xyz.

None of that LES xxx,xxx stuff.

EG:


C:

int *ptr = malloc(sizeof (int));


ASSEMBLER:

movl ptr,%eax   // places the address of what is pointer to into eax
movl $ptr,%eax  // places the address of the pointer into eac

and with an address in eax:

movl (%eax),%ebx  // loads ebx with the int eax points to

I don't remember if

movl (ptr),%ebx  

will work directly (probably will, try it and see)

>	Joonas

ABW
--
I have become... Comfortably numb...

Alaric B. Williams Internet : alaric AT abwillms DOT demon DOT co DOT uk
<A HREF="http://www.hardcafe.co.uk/Alaric/">http://www.hardcafe.co.uk/Alaric/</A>