It seems even a hello world program depends on several libraries:
libc.so.6 => /lib64/libc.so.6 (0x00000034f4000000)
/lib64/ld-linux-x86-64.so.2 (0x00000034f3c00000)
How can I static link all stuff ?
2 Answers
Link with -static. "On systems that support dynamic linking, this prevents linking with the shared libraries."
Edit: Yes this will increase the size of your executable. You can go two routes, either do what Marco van de Voort recommends (-nostdlib, bake your own standard library or find a minimal one).
Another route is to try and get GCC to remove as much as it can.
gcc -Wl,--gc-sections -Os -fdata-sections -ffunction-sections -ffunction-sections -static test.c -o test
strip test
Reduces a small test from ~800K to ~700K on my machine, so the reduction isn't really that big.
Previous SO discussions:
Garbage from other linking units
How do I include only used symbols when statically linking with gcc?
Using GCC to find unreachable functions ("dead code")
Update2: If you are content with using just system calls, you can use gcc -ffreestanding -nostartfiles -static to get really small executable files.
Try this file (small.c):
#include <unistd.h>
void _start() {
char msg[] = "Hello!\n";
write(1, msg, sizeof(msg));
_exit(0);
}
Compile using: gcc -ffreestanding -nostartfiles -static -o small small.c && strip small. This produces a ~5K executable on my system (which still has a few sections that ought to be stripable). If you want to go further look at this guide.
4 Comments
James O'Doherty
The size is so large because instead of simply including mere references to the functions and code from the shared libraries, the statically linked program actually includes copies of the libraries and their code.
lexer
@James O'Doherty ,how do I instruct the compiler to only include neccesary symbols?
Marco van de Voort
The --gc-sections and other section commands in the answer should do that.
David X
@lexer(1), try reading http://www.muppetlabs.com/~breadbox/software/tiny/teensy.html (and probably other stuff in http://www.muppetlabs.com/~breadbox/software/tiny/).
Or use -nostdlib and implement your own libraries and startup code.
The various "assembler on *nix" sites can give you an idea how to do it.
If you just want your binary to be small, start by using 32-bit.
answered Aug 15, 2011 at 12:36
Marco van de Voort
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libc.so.6andld-linux-x86-64.so.2are part of it. Did you ever see embedded linux without rootfs?