Compiled C++ executables HUGE?

After programming for a while in C, I decided to finally start to learn C++. This is sort of bothering me, as the standard 'hello world' in C is usuall开发者_高级运维y ~16KB, including all of the crud your compiler throws on there. (Using stdio)

However, when I create a C++ executable doing hello world, the file is ~470KB! I went ahead and used cstdio instead of iostream, thinking it would make a difference and it did.

My question is: When I include iostream, why does the size of my executable explode?

Edit: I'm using G++ (With the Dev-CPP IDE, but I can figure out how to add CL paramaters)

In a word, symbols.

The C++ standard library introduces a lot of symbols to your program, since most of the library exists primarily in the header files.

Recompile your program in release mode and without debug symbols, and you can easily expect the program to be significantly smaller. (Smaller still if you strip symbols.)

As a quick demonstration of this fact, observe:

$ cat hello.c
#include <stdio.h>
int main() {
    printf("%s\n", "Hello, world!");
    return 0;
}
$ cat hello.cpp
#include <iostream>
int main() {
    std::cout << "Hello, world!\n";
    return 0;
}
$ gcc hello.c -o hello-c
$ g++ hello.cpp -o hello-cpp
$ gcc hello.c -ggdb -o hello-c-debug
$ g++ hello.cpp -ggdb -o hello-cpp-debug
$ gcc hello.c -s -o hello-c-stripped
$ g++ hello.cpp -s -o hello-cpp-stripped
$ gcc hello.c -s -O3 -o hello-c-stripped-opt
$ g++ hello.cpp -s -O3 -o hello-cpp-stripped-opt
$ ls -gG hello*
-rwxr-xr-x 1  6483 Nov 14 15:39 hello-c*
-rw-r--r-- 1    79 Nov 14 15:38 hello.c
-rwxr-xr-x 1  7859 Nov 14 15:40 hello-c-debug*
-rwxr-xr-x 1  7690 Nov 14 15:39 hello-cpp*
-rw-r--r-- 1    79 Nov 14 15:38 hello.cpp
-rwxr-xr-x 1 19730 Nov 14 15:40 hello-cpp-debug*
-rwxr-xr-x 1  5000 Nov 14 15:45 hello-cpp-stripped*
-rwxr-xr-x 1  4960 Nov 14 15:41 hello-cpp-stripped-opt*
-rwxr-xr-x 1  4216 Nov 14 15:45 hello-c-stripped*
-rwxr-xr-x 1  4224 Nov 14 15:41 hello-c-stripped-opt*

I can't explain why a Windows build of the programs with G++ produces such large executables, but on any other platform, symbols are the primary driving factor in large file sizes. I don't have access to a Windows system at the moment, so I can't test.

Becuase you've dragged in most of the standard library by using iostreams. It's a one off thing though so as your programs gets larger it will seem less and less of an overhead.

However you probably want to compile using a shared library version of the standard library and most compilers / operating systems will let you do this so you'll not have to include all of the standard library in your executable. Which compiler are you using and we can likely advise on how to do that.

On windows with VC command line, use the /MD command line option for example.

I would guess that by including <iostream> you're indirectly including many parts of the STL, such as <string> which in turn includes <vector> etc.

This is more an artifact of the compiler (and options) you use than almost anything else. With MS VC++, depending on the compiler flags I use I can get anywhere from ~8K to ~110K. Using MinGW, I get around 24-25K (again, depending on flags).

Just in case you're wondering, I'd guess the larger range I get with VC++ is mostly a result of knowing its flags better. MinGW might only cover a smaller range even if I knew it better, but due to my limited knowledge of its flags I'm accepting most of what it does by default; I know how to turn optimization on and off, but have to look at things pretty carefully to do a lot more than that.

MinGW (g++) compiles really big files.
For example the same "hello world" program with iostreams compiles to ~100KB by VC++ (with statically linked CRT) and to ~470KB by g++.

This is one aspect of the fake C++ interview that is actually kind of true :)

You know, when we had our first C++ compiler, at AT&T, I compiled 'Hello World', and couldn't believe the size of the executable. 2.1MB

What? Well, compilers have come a long way, since then.

They have? Try it on the latest version of g++ - you won't get much change out of half a megabyte.