5.1. nm utas?疽

Az nm(1) utas?疽 megmutatja milyen szimb?umok tal疝hat?k egy adott programk?yvt疵ban. Mind statikus, mind megosztott programk?yvt疵akra m??ik. Egy adott programk?yvt疵ra az nm(1) a szimb?umok neveit, 駸 minden szimb?um t?us疸 駸 駻t駝騁 k駱es megmutatni. Azt is k駱es meghat疵ozni, hogy a forr疽k?ban hol volt a szimb?um WIDTH="100%" >

nm -o /lib/* /usr/lib/* /usr/lib/*/* \
      /usr/local/lib/* 2> /dev/null | grep 'cos$' 

A megosztott programk?yvt疵akat tilos a gcc "-nostartfiles" vagy "-nostdlib" kapcsol?val ford?ani. Ha ezeket haszn疝juk a konstruktor/destruktor (dlclose() megh?疽疱al, amikor az a referencia sz疥l? 0-ra 疝l?ja vagy a program norm疝is kil駱駸ekor). A C protot?usok: /usr/lib/libc.so f疔lja:

void _init(void); void _fini(void);

/* GNU ld script Use the shared library, but some functions are only in the static library, so try that secondarily. */ GROUP ( /lib/libc.so.6 /usr/lib/libc_nonshared.a )

Tov畸bi inform當i? tal疝sz err? a ld texinfo dokument當i?畸an a (Typically references to external functions are bound on an as-needed basis, and are not all bound when the application starts up.) Ha a megosztott programk?yvt疵 r馮i, az ig駭yelt interf駸ze hi疣yozhat, amikor az alkalmaz疽 megpr?疝ja haszn疝ni azt. Ez azonnali 駸 v疵atlan hib疸 okozhat.

http://www.gnu.org/manual/ld-2.9.1/html_node/ld_25.html honlapon.

5.5. GNU libtool

Ha olyan alkalmaz疽t k駸z?esz amit t?b rendszerre szeretn駘 haszn疝ni, akkor javasolt a GNU libtool

/* Explain here what foobar does */

#ifndef FOOBAR_H
#define FOOBAR_H

#ifdef __cplusplus
extern "C" {
#endif

 ... header code for foobar goes here ...

#ifdef  __cplusplus
}
#endif
#endif

 $ lsbappchk myapplication

6. Tov畸bi p駘d疚

Az al畸bi p駘d疚 mindh疵om programk?yvt疵 t?ussal foglalkoznak (statikus, megosztott 駸 dinamikus programk?yvt疵ak). A libhello.c f疔l egy trivi疝is programk?yvt疵, a libhello.h header-rel. A demo_use.c f疔l egy trivi疝is program, ami a programk?yvt疵at haszn疝ja. Ezt k?etik a dokument疝t szkriptek (script_static 駸 script_dynamic), amik bemutatj疚, hogyan haszn疝hatod a programk?yvt疵at megosztott illetve statikus programk?yvt疵k駭t. Ezut疣 a demo_dynamic.c f疔ljal 駸 a script_dynamic szkripttel megmutatjuk, COLOR="#000000" >

/* libhello.c - demonstrate library use. */

#include <stdio.h>

void hello(void) {
  printf("Hello, library world.\n");
}

6.2. libhello.h f疔l

/* libhello.h - demonstrate library use. */ void hello(void);

6.3. demo_use.c f疔l

/* demo_use.c -- demonstrate direct use of the "hello" routine */ #include "libhello.h" int main(void) { hello(); return 0; }

6.4. script_static f疔l

#!/bin/sh # Static library demo # Create static library's object file, libhello-static.o. # I'm using the name libhello-static to clearly # differentiate the static library from the # dynamic library examples, but you don't need to use # "-static" in the names of your # object files or static libraries. gcc -Wall -g -c -o libhello-static.o libhello.c # Create static library. ar rcs libhello-static.a libhello-static.o # At this point we could just copy libhello-static.a # somewhere else to use it. # For demo purposes, we'll just keep the library # in the current directory. # Compile demo_use program file. gcc -Wall -g -c demo_use.c -o demo_use.o # Create demo_use program; -L. causes "." to be searched during # creation of the program. Note that this command causes # the relevant object file in libhello-static.a to be # incorporated into file demo_use_static. gcc -g -o demo_use_static demo_use.o -L. -lhello-static # Execute the program. ./demo_use_static

6.5. script_shared f疔l

#!/bin/sh # Shared library demo # Create shared library's object file, libhello.o. gcc -fPIC -Wall -g -c libhello.c # Create shared library. # Use -lc to link it against C library, since libhello # depends on the C library. gcc -g -shared -Wl,-soname,libhello.so.0 \ -o libhello.so.0.0 libhello.o -lc # At this point we could just copy libhello.so.0.0 into # some directory, say /usr/local/lib. # Now we need to call ldconfig to fix up the symbolic links. # Set up the soname. We could just execute: # ln -sf libhello.so.0.0 libhello.so.0 # but let's let ldconfig figure it out. /sbin/ldconfig -n . # Set up the linker name. # In a more sophisticated setting, we'd need to make # sure that if there was an existing linker name, # and if so, check if it should stay or not. ln -sf libhello.so.0 libhello.so # Compile demo_use program file. gcc -Wall -g -c demo_use.c -o demo_use.o # Create program demo_use. # The -L. causes "." to be searched during creation # of the program; note that this does NOT mean that "." # will be searched when the program is executed. gcc -g -o demo_use demo_use.o -L. -lhello # Execute the program. Note that we need to tell the program # where the shared library is, using LD_LIBRARY_PATH. LD_LIBRARY_PATH="." ./demo_use

6.6. demo_dynamic.c f疔l

/* demo_dynamic.c -- demonstrate dynamic loading and use of the "hello" routine */ /* Need dlfcn.h for the routines to dynamically load libraries */ #include <dlfcn.h> #include <stdlib.h> #include <stdio.h> /* Note that we don't have to include "libhello.h". However, we do need to specify something related; we need to specify a type that will hold the value we're going to get from dlsym(). */ /* The type "simple_demo_function" describes a function that takes no arguments, and returns no value: */ typedef void (*simple_demo_function)(void); int main(void) { const char *error; void *module; simple_demo_function demo_function; /* Load dynamically loaded library */ module = dlopen("libhello.so", RTLD_LAZY); if (!module) { fprintf(stderr, "Couldn't open libhello.so: %s\n", dlerror()); exit(1); } /* Get symbol */ dlerror(); demo_function = dlsym(module, "hello"); if ((error = dlerror())) { fprintf(stderr, "Couldn't find hello: %s\n", error); exit(1); } /* Now call the function in the DL library */ (*demo_function)(); /* All done, close things cleanly */ dlclose(module); return 0; }

6.7. script_dynamic f疔l

#!/bin/sh # Dynamically loaded library demo # Presume that libhello.so and friends have # been created (see dynamic example). # Compile demo_dynamic program file into an object file. gcc -Wall -g -c demo_dynamic.c # Create program demo_use. # Note that we don't have to tell it where to search for DL libraries, # since the only special library this program uses won't be # loaded until after the program starts up. # However, we DO need the option -ldl to include the library # that loads the DL libraries. gcc -g -o demo_dynamic demo_dynamic.o -ldl # Execute the program. Note that we need to tell the # program where get the dynamically loaded library, # using LD_LIBRARY_PATH. LD_LIBRARY_PATH="." ./demo_dynamic