Executable size

Ever downloaded a crackme or a program and realized how huge it was and it was only doing something really simple? I did and unfortunately I even released my own programs and they were full of bloat. In this article I’m going to show you 3 steps that I always do now when I build a final version of my programs.

I’m using MVC++ 6 as my complier, but the tricks that I am going to do can be done in other compliers as well. Okay let’s start of with a simple “Hello World” program.

#include “stdio.h”
int main(void)
{
printf(“hello, world\n”);
return 0;
}

Without touching my complier settings, the executable size is: 152kb Thats a lot for a simple Hello World program. And if you open it in an disassembler, you will see that there’s so much bloat.

1st step
You need to do a “Release build” instead of a “Debug build” This will reduce the size dramatically. You can do that by going to Build -> Set Active Configuration and click Win32 Release.

Okay now let’s build it again! And a new folder named “Release” has appeared and the executable is now 28kb, we reduced the size 5 and half times!

Step 2
Now we are going to modify settings. Goto Project -> Settings -> Click the “Link” tab. Now look at the edit box where it says “Object/library modules”

Okay now remove everything from there and type “MSVCRT.LIB kernel32.lib user32.lib” and build. The executable size is now: 16kb. This is very important! only using those 3 libraries will cause some of your API not to work. For example, RegOpenKeyEx Why? Because it needs “Advapi32.lib” How do you know? Go to the API MSDN page, scroll all the way down till you see the “Requirements” So now all you need to do is add the required library.

Step 3
This is really not hard, goto Project -> Settings -> click the link tab and now see that big edit box? Add this line “/ALIGN:4096″ there. Build, and the executable size is now 2.50kb! and we started at 152kb.

You can learn about this linker option at MSDN: /ALIGN

Now you executable is small and not full with bloat. You can open it in an assembler and you will see its more cleaner and sleek. I gave you my 3 steps that I always do, however a simple google search will show you more in depth tricks to reduce the size to 1kb and less! Thanks for reading. And I’m almost done writing a article about hooking Nt* functions, will publish later today.

Later.