How to decrease the size of generated binaries?

Question

I know that there is an option \"-Os\" to \"Optimize for size\", but it has little affect, or even increase the size on some occasion :(

strip (or \"-s\" option) remov

Answer 1

You can also use -nostartfiles and/or -nodefaultlibs or the combo of both -nostdlib. In case you don't want a standard start file, you must write your own _start function then. See also this thread (archived) on oompf:

(quoting Perrin)

# man syscalls
# cat phat.cc
extern "C" void _start() {
        asm("int $0x80" :: "a"(1), "b"(42));
}
# g++ -fno-exceptions -Os -c phat.cc
# objdump -d phat.o

phat.o:     file format elf64-x86-64

Disassembly of section .text:

0000000000000000 <_start>:
   0:   53                      push   %rbx
   1:   b8 01 00 00 00          mov    $0x1,%eax
   6:   bb 2a 00 00 00          mov    $0x2a,%ebx
   b:   cd 80                   int    $0x80
   d:   5b                      pop    %rbx
   e:   c3                      retq
# ld -nostdlib -nostartfiles phat.o -o phat
# sstrip phat
# ls -l phat
-rwxr-xr-x 1 tbp src 294 2007-04-11 22:47 phat
# ./phat; echo $?
42

Summary: Above snippet yielded a binary of 294 bytes, each byte 8 bits.