Very Computer

Hi,

I have come upon a  problem and due to lack of documentation (or
persistence in finding it :)) I need to know :
- How are the symbols exported from a shared/static library?

RSVP, TIA,
SS

Depend on the language used.

You can see which one are with the tool nm

$ nm --extern-only myobj.?[oa]

: Hi,

: I have come upon a  problem and due to lack of documentation (or
: persistence in finding it :)) I need to know :
: - How are the symbols exported from a shared/static library?

They are exported. Period. Unless you define variable as static (and
thus constrain its visibility to one source file, it would be exported.
Functions are always exported by default.

It is much more complicated to avoid exporting symbols from unix shared
library than vice versa.
: RSVP, TIA,
: SS

--

I don't answer questions by private E-Mail from this address.

By default, all external symbols are exported from a shared and static
libraries in Linux.  If you need to limit the symbols exported in a
shared library use a version script.  AFAIK there is no way to do this
for static libraries.

Attatched is an example of creating a shared library with and without
a version script.  (ripped from a message I posted back in August).

-K

slib1.h -------------------------------------------------

extern int slib_i;

int slib00();
int slib01();
int slib02();  

slib1.c --------------------------------------------------

#include <stdio.h>

int slib_i=5;

int slib00() { printf("slib00\n"); }
int slib01() { printf("slib01\n"); }
int slib02() { printf("slib02\n"); }

main.c -----------------------------------------------------

#include <stdio.h>

#include "slib1.h"

int main()
{
    int i = slib_i;
    slib00();
    slib01();
    slib02();

Quote:}                  

libslib1.ver ------------------------------------------------

#
# Export file for libslib1_ver
#
libslib1_ver.so.1.0 {
    global:
        slib_i;
        slib00;
        slib01;
        slib02;
    local:
        *;

Quote:};      

Makefile ---------------------------------------------------

all: main main_ver

main: main.c libslib1.so.1.0
        gcc -o main main.c -L. -lslib1

main_ver: main.c libslib1_ver.so.1.0
        gcc -o main_ver main.c -L. -lslib1_ver

libslib1.so.1.0 : slib1.c
        gcc -c -fPIC slib1.c
        gcc -shared -Wl,-soname,libslib1.so.1 -o libslib1.so.1.0 slib1.o        
        ln -sf libslib1.so.1.0 libslib1.so.1
        ln -sf libslib1.so.1.0 libslib1.so

libslib1_ver.so.1.0 : slib1.c libslib1.ver
        gcc -c -fPIC slib1.c
        gcc -shared -Wl,-soname,libslib1_ver.so.1,-version-script=libslib1.ver -o libslib1_ver.so.1.0 slib1.o        
        ln -sf libslib1_ver.so.1.0 libslib1_ver.so.1
        ln -sf libslib1_ver.so.1.0 libslib1_ver.so

clean:
        rm -f *.o *.a *.so *.so.* *~ main main_ver

-------------------------------------------------------------

--
Kelly R. Burkhart

(H)ow do you give Microsoft the benefit of the doubt when you know that if
you throw it into a room with truth, you'd risk a matter/anti-matter
explosion?
   -- Nicholas Petreley