RE: gcc -static pulls in entire libs

["Trawick, James" <James_Trawick@tvratings.com>]

(sorry Serban, just filling the question out a little...  it is a curious
phenominon)

Consider the following C source:

/* begin test.c */

#ifdef DO_SIN
#include <math.h>
#endif

#ifdef DO_PRINTF
#include <stdio.h>
#endif

int main(){

#ifdef DO_SIN
	sin(0);
#endif

#ifdef DO_PRINTF
	printf("baz!\n");
#endif

}

/* end test.c */

compiled several different ways:

for d1 in "" -DDO_PRINTF
do
for lm in "" -lm
do
for d2 in "" -DDO_SIN
do
for static in "" -static
do
gcc -Os $d1 $d2 test.c -o testproc$static$lm$d1$d2 $lm $static
done
done
done
done

(ignoring the errors when libm isn't linked in of course) We get the
following executables:

-rwxr-xr-x    1 root     root        13629 Jan 18 09:56 testproc*
-rwxr-xr-x    1 root     root        13739 Jan 18 09:56 testproc-DDO_PRINTF*
-rwxr-xr-x    1 root     root        13637 Jan 18 09:56 testproc-lm*
-rwxr-xr-x    1 root     root        13763 Jan 18 09:56
testproc-lm-DDO_PRINTF*
-rwxr-xr-x    1 root     root        13878 Jan 18 09:56
testproc-lm-DDO_PRINTF-DDO_SIN*
-rwxr-xr-x    1 root     root        13768 Jan 18 09:56 testproc-lm-DDO_SIN*
-rwxr-xr-x    1 root     root      1712216 Jan 18 09:56 testproc-static*
-rwxr-xr-x    1 root     root      1713259 Jan 18 09:56
testproc-static-DDO_PRINTF*
-rwxr-xr-x    1 root     root      1712216 Jan 18 09:56 testproc-static-lm*
-rwxr-xr-x    1 root     root      1713259 Jan 18 09:56
testproc-static-lm-DDO_PRINTF*
-rwxr-xr-x    1 root     root      1713413 Jan 18 09:56
testproc-static-lm-DDO_PRINTF-DDO_SIN*
-rwxr-xr-x    1 root     root      1712402 Jan 18 09:56
testproc-static-lm-DDO_SIN*

When linked statically, it appears that there's no difference in sizes
whether one links in libm or not, nor when you're doing nothing at all (as
in testproc-static).  I think the linker is doing good as far as not linking
unneeded symbols goes, but there appears to be some sort of process
initialization that requires a whole bunch of other stuff.

I don't know if this is a question for gcc, binutils, glibc, or linux
itself, but what exactly is happening behind the scenes?  What's being
initialized?  Is there a way to reduce or eliminate the amount of resulting
static code?  Is that a good idea?

chris

-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org]On
Behalf Of Serban Simu
Sent: Thursday, January 17, 2002 3:13 PM
To: gcc-help@gcc.gnu.org
Subject: gcc -static pulls in entire libs


Hi,

I found that "gcc -static" creates oversized binaries, possibly pulling in
entire libraries rather than the necessary sections.

I have the object file s.o, which uses libmath. I link it as follows, to
produce the binaries s1, s2 and s3:

    $ gcc -o s1 s.o /usr/lib/libm.a
    $ gcc -o s2 -static s.o /usr/lib/libm.a
    $ gcc -o s3 -static s.o -lm
    $ ls -l s1 s2 s3
    -rwxr-xr-x    1 serban   serban       5920 Jan 17 03:23 s1
    -rwxr-xr-x    1 serban   serban     443521 Jan 17 03:23 s2
    -rwxr-xr-x    1 serban   serban     443521 Jan 17 03:23 s3

I'm using gcc version 2.95.4 20010703 (Debian prerelease)

This behavior seems incorrect. Moreover, in case the system provides both .a
and .so versions of the libraries, there is no workaround for using the -lm
syntax. Without -static gcc will build the dynamically linked binary, and
with -static it builds an oversized binary. "strip" only reduces its size a
little bit:

    $ strip s2
    $ ls -l s2
    -rwxr-xr-x    1 serban   serban     397536 Jan 17 03:48 s2

Is there a way to use the -lm syntax, with the -static option, but create
the small binary? Are there any other options that will help not pull in the
entire lib?

I would appreciate any info to help me understand this. Thank you!

Serban Simu
Software Eng., Digital Fountain