From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Massive c++ execs.
Date: Tue, 21 Oct 1997 20:39:13 +0000
Organization: Two pounds of chaos and a pinch of salt
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Message-ID: <344D12F1.614E@cs.com>
References: <62ilp8$mkk AT paperboy DOT ccc DOT nottingham DOT ac DOT uk>
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To: djgpp AT delorie DOT com
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student AT nottingham DOT ac DOT uk wrote:
> 
> Hi there. Could anyone tell me why, when I compile a 123 byte c++ program
> with the GNU compiler, I get a 200k+ executable?
>  This is the test code:
> 
>  #include <iostream.h>
>  #include <conio.h>

It's these two that kill you.  A basic "hello, world" program written in
C will compile to about 55k; when you use C++, you add another 50-60k,
and the use of getch() adds another big chunk because the conio
functions come as part of a single library unit.

Basically, in using the full power of a 32-bit protected mode compiler
to print eleven characters to the screen, you are swatting a fly with a
sledgehammer.

There are, however, many ways to reduce the size of DJGPP programs; the
best place to look is in chapter 8.15 of the Frequently Asked Questions
list (v2/faq210b.zip from SimTel or online at
http://www.delorie.com/djgpp/v2faq/).  The full explanation is too long
for a simple post, but the basics include:

 - Use the '-s' compiler switch to remove the debugging information from
the executable.
 - Optimize the code with the '-O' switch and its variants.
 - Define empty versions of certain large functions in the startup code
that may not be needed by all programs.
 - Use the djp executable packer to runtime compress your programs.

This combination can reduce the final size of a "Hello, World" program
written in C to about 20k.  Still, you are wasting a tremendous amount
of effort.

Some additional commentary:

>  void main()

This is an illegal construct.  main() must always return an integer;
this value is used by the startup code and returned to the operating
system as the program's exit code.  If you use the '-Wall' switch in a
C++ program, the compiler will notify you of this.

>  {
> 
>   cout << "Hi there!!\n";
>   getch();

Be careful mixing conio functions with stdio functions.  This doesn't
bite you here because you printed a newline character, but try omitting
it!  As usual, the FAQ has an answer in chapter 9.4.

>   // test comment
> 
>  }

Since main() returns an integer, you need to include a "return 0;"
statement to indicate that your program ran successfully.

> This is the command line to compile it :
> 
>  gcc -v main.cc -o testcpp.exe -lgpp

Some other good parameters to use, for beginners and advanced users
alike, are '-Wall', to display extra warnings for common programming
mistakes, '-O' to optimize your code (reducing size and increasing
speed), and '-g' to add additional symbol information required if you
attempt to debug your program with a debugger like gdb or RHGDB.

> 200K+ to print a single line and wait for a key seems very odd to me.
>  Am I doing some thing wrong, or does gcc add in extra unneccessary
> libraries?

In fact, gcc adds in only what is necessary for your program to run, or
every program would be over 600k long!

hth

-- 
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