static executable bloat

[Zack Weinberg <zack@bitmover.com>]

H.J. Lu wrote:
> > This is what I'm trying to solve:
> > 
> > $ cat t1.c
> > int main(void) { return 0; }
> > $ cat t2.c
> > int main(void) { return 0; }
> > 
> > void abort(void) { while(1); }
> > void atexit(void *x) { return; }
> > void exit(int x) { _exit(x); }
> > 
> > void *__libc_stack_end;
> > $ gcc -static t1.c -o t1
> > $ gcc -static t2.c -o t2
> > $ ls -l t1 t2
> > -rwxrwxr-x   1 zack     zack       222102 Aug 18 09:12 t1
> > -rwxrwxr-x   1 zack     zack         6215 Aug 18 09:12 t2
> > 
> > I want t1 to not be 220k.  The problem appears to be that the
> > implementations of abort and atexit suck in all kinds of stuff
> > transitively - mainly via libio.  I thought, late last night, that it
> > had to do with pthreads being referenced despite those being weak
> > symbols, but I was wrong.
> > 
> 
> Add -Wl,-Map,map. You should see what/why they are included in "map".

Yes, that works beautifully, thank you.

The problem is nothing to do with weak symbols.  It's very simple:

- abort flushes all open FILEs, so it pulls in stdio
- atexit and exit refer to malloc, and the malloc checking code pulls
  in stdio
- __libc_stack_end is defined only in dl-support.c, which pulls in the
  rest of the static libdl, which uses stdio

and

- stdio is 100k by itself
- the wide char support in stdio references the gconv infrastructure and
  the static libdl, which (with everything that uses) is another 100k

I spent a lot of time today bashing at this, but there is no easy fix.
I guess this is just a "libio should be smaller" whine.  Note that an
awful lot of places in there know when a stream is wide; it seems to
me that this ought to be hidden in the jump table.  There's no reason
why not to redirect _IO_setb instead of having _IO_setb and _IO_wsetb,
for example.

zw