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From: Brian Drummond <brian@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Can I get rid of C libraries dependencies?
Date: Thu, 17 Sep 2015 10:25:23 +0000 (UTC)
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On Thu, 17 Sep 2015 01:13:47 -0700, Leff Ivanov wrote:

> среда, 16 сентября 2015 г., 19:13:11 UTC+3 пользователь Simon Wright
> написал:
>> Leff Ivanov <droiddermo@gmail.com> writes:
>> 
>> > What I want to achive is a tiny 2kb binary executable
>> 
>> Can you tell us a little more about why you need to do this, what OS
>> you're using ...
> 
> I'm using windows and want to write tiny tools in Ada like I can write
> one in C/C++ using -nostdlib flag and directly linking to OS specific
> libraries. The same can be applied to Linux and Mac OSX as well, but
> currently I'm focusing on Windows.
> 
> If I do "gnatmake -a -f -nostdlib main.adb" I can see that GNAT actually
> recompiles a lot of stuff from RTS, like a-except.adb,
> s-secsta.abd and etc. So the No_Run_Time pragma cuts off only a part of
> Ada RTS, but leaves the rest.
> 
> Gnatlink tool with -nostdlib returns a lot of undefined references to C
> code, which I want to get rid off. It seems that mostly it is functions
> that implements exceptions, like _Unwind_SjLj_Register,
> __gnat_personality_sj0 and etc.

There are pragmas to restrict the use of exceptions : these should reduce 
the undefined references.
 
> Undefined references to stuff like memmove and memcmp I can simply fix
> by linking directly with libmsvcrt.a, so theese functions would be taked
> from standard windows msvcrt.dll library.  But there's also undefined
> reference to __chkstk_ms, this function seem to check if the stack is
> full. 

One way is to specify your own RTS, with the "--RTS=path/to/rts" option. 
Then you would need to create your own RTS, which in this case would be 
your wrapper that handles anything you can't link directly like memcpy 
etc. You can get a handle on how this works by studying the AVR-Ada 
microcontroller port, which is quite capable of generating executables 
down to a couple of hundred bytes.

-- Brian