Xref:	news2.mv.net comp.os.msdos.djgpp:6756
From:	alaric AT abwillms DOT demon DOT co DOT uk (Alaric B. Williams)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: __attribute__((section))
Date:	Fri, 02 Aug 1996 19:13:38 GMT
Lines:	121
Message-ID:	<839013106.23117.0@abwillms.demon.co.uk>
References:	<Pine DOT NEB DOT 3 DOT 93 DOT 960731121214 DOT 7438B-100000 AT ananke DOT amu DOT edu DOT pl> <838840319 DOT 11194 DOT 2 AT abwillms DOT demon DOT co DOT uk>
NNTP-Posting-Host:	abwillms.demon.co.uk
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

alaric AT abwillms DOT demon DOT co DOT uk (Alaric B. Williams) wrote:

>Mark Habersack <grendel AT ananke DOT amu DOT edu DOT pl> wrote:

>>On Mon, 29 Jul 1996, Helge Kruse wrote:
>>The hack is OK, but where does MYDATA section go? Does it go to separate
>>segment when proggy is loaded? If so, you have to use far pointers/switch DS
>>selector if you want to access the data - BY HAND.

>Is this really true?

>I mean, will the stub actually allocate seperate selectors with DPMI
>for other sections, or just load all those sections into the same
>virtual address space, as I thought?

I'm vindicated! The following will print the value 123 on screen, as
expected!

I hope it's useful for anyone else fiddling with their own sections.
There was an (unofficial) patch posted here a while ago to fix gcc's
__attribute__ ((section)) problem - I haven't checked it out yet, but
it'll go in my hardware ints tutorial...


Enjoy,


ABW

=============DJGPP.LNK:

OUTPUT_FORMAT("coff-go32")
ENTRY(start)
SECTIONS
{
  .text  0x1000+SIZEOF_HEADERS : {
    *(.text)
    etext  =  . ; _etext = .;
    sltext = . ;
    *(.ltxt)
    eltext = . ;
    . = ALIGN(0x200);
  }
  .data  ALIGN(0x200) : {
    djgpp_first_ctor = . ;
    *(.ctor)
    djgpp_last_ctor = . ;
    djgpp_first_dtor = . ;
    *(.dtor)
    djgpp_last_dtor = . ;
    *(.data)
     edata  =  . ; _edata = .;
    sldata = . ;
    *(.ldat)
    eldata = . ;
     . = ALIGN(0x200);
  }
  .bss  SIZEOF(.data) + ADDR(.data) :
  { 					
    *(.bss)
    *(COMMON)
     end = . ; _end = .;
     . = ALIGN(0x200);
  }
}

=========MAKEFILE:

sections.exe : sections.S sect.cc
	gcc -g sections.S sect.cc -liostr -o sections

=========SECT.CC

#include <dpmi.h>
#include <go32.h>
#include <iostream.h>

#define LOCKED_VAR section (".ldat"), nocommon
#define LOCKED_FUNC section (".ltxt")

extern int sltext __asm__("sltext");
extern int eltext __asm__("eltext");
extern int sldata __asm__("sldata");
extern int eldata __asm__("eldata");

void lock_everything() {
   _go32_dpmi_lock_data(&sldata,(long)&eldata - (long)&sldata);
   _go32_dpmi_lock_code(&sltext,(long)&eltext - (long)&sltext);
}

extern "C" int my_var;
extern "C" void my_func(void);

main() {
   lock_everything();
   cout << my_var;
   my_func();
}

==============SECTIONS.S

..section .ldat

..globl _my_var

_my_var:  .long 123

..section .ltxt

..globl _my_func

_my_func:
   ret


--
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>

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