code generation

[John-Mark Gurney]

Jack Raats wrote this message on Sat, May 30, 2020 at 23:52 +0200:
> Hi,
> 
> Can anyone explain why a simple hello_world.c compiles on a AMD64 machine
> to +/- 21000 bytes while on a raspberry pi 3 +/- 206000 bytes (10 times
> more)
> 
> I use FreeBSD 12.1 stable on RPi3 and cc -o hello hello.c to compile.

What file, and what's your compiler options.  This is on 13-current,
but shouldn't be dramatically different.  it's on a Pine64 A64-LTS,
but that shouldn't mater either.

freebsd at generic:~ $ cat hello.c
#include <stdio.h>

int
main(void)
{

	printf("hello world\n");

	return 0;
}
freebsd at generic:~ $ cc -o hello hello.c
freebsd at generic:~ $ ls -l hello
-rwxr-xr-x  1 freebsd  freebsd  14232 Jan  1 16:14 hello
freebsd at generic:~ $ ./hello
hello world

This is even smaller when you strip it:
freebsd at generic:~ $ strip hello
freebsd at generic:~ $ file hello
hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (FreeBSD), dynamically linked, interpreter /libexec/ld-elf.so.1, for FreeBSD 13.0 (1300094), FreeBSD-style, stripped
freebsd at generic:~ $ ls -l hello
-rwxr-xr-x  1 freebsd  freebsd  5456 Jan  1 16:19 hello

Though on the other hand, compile it static and:
freebsd at generic:~ $ cc -o hello hello.c -static -O2
freebsd at generic:~ $ ls -l hello
-rwxr-xr-x  1 freebsd  freebsd  4229680 Jan  1 16:14 hello

4MB seems a bit huge for a statically compiled program...

But that's because of debug symbols:
freebsd at generic:~ $ cc -o hello hello.c -static -O2
freebsd at generic:~ $ file hello
hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (FreeBSD), statically linked, for FreeBSD 13.0 (1300094), FreeBSD-style, with debug_info, not stripped
freebsd at generic:~ $ strip hello
freebsd at generic:~ $ ls -l hello
-rwxr-xr-x  1 freebsd  freebsd  701808 Jan  1 16:17 hello

But even stripped, it's still VERY large...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."