From: "Stefan Viljoen" <rylan AT intekom DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Some questions
Date: Sat, 4 Dec 1999 09:12:17 +0200
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Alexey Gaev <Alexey DOT Gaev AT p25 DOT f21 DOT n452 DOT z2 DOT fidonet DOT org> wrote in message
news:944167327 AT p25 DOT f21 DOT n452 DOT z2 DOT FIDOnet DOT ftn...

>   Second question: Is there any kind of Language Reference in the package?
For
> example, I want to know if I can tell the compiler to pass values to
functions
> in specified registers, like I did in WATCOM: #pragma aux MyFunc parm
[eax]...

This is not strictly a "DJGPP" question (huh?!) When you are looking to
interface GCC with assembly code in DJGPP, as regards parameter passing you
just declare the function prototype in C like you were coding it in C

void test(int param1, int param2);

then, if for example you are using NASM to do the external assembly, you
just pop the parameters off the stack - each is
stored as a doubleword. To access param1

push        ebp
mov        ebp,esp

mov    eax,[ebp]        ;param1 in eax
mov    ebx,[ebp+4]    ;param2
mov    ebx,[ebp+8]    ;+8 gives param3
mov    ebx,[ebp+12]    ;+12 gives param4

mov        esp,ebp
pop        ebp
ret

Untested! Check these for accuracy. Function result you want to return into
a DJGPP module goes into eax. Hope this is correct and helps some!

>   Third: is there any way to link programs on DJGPP with .obj files,
created,
> for example, by TASM?

Not that I am aware of - M$'s .OBJ fle format is incompatible with the COFF
format which is DJGPP object format. You have to either convert external
code into DJGPP compilable C code, or if it is external assembly convert it
to NASM or DJGPP's inline AT&T assembly. (shudder!)

>   And, finally: don't you think that 104 Kb for "Hello, world" program,
even
> with debug information, is too much? ;) WATCOM C gives me 31 Kb in the
same
> conditions (of course, not counting dos4gw.exe ;).

There are two ways in which you can get a hello world down to +- 30k
(exactly Watcom size):

1. Use the -s switch on the GCC command line.

The -s switch strips debug info from the final .EXE:

gcc -o test.exe test.c -s

2. Use an .EXE file compressor like DJP or UPX.

DJP can be found on the same sites where DJGPP is downloadable from - it is
a very nice EXE file compressor that can compress DJGPP .EXE files very
well. UPX is a universal .EXE file compressor that is reputed to be quite
nice too.

Hope this helped some!


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