.\" -*- nroff -*-
.\" Copyright 1995 Yggdrasil Computing, Incorporated.
.\" written by Adam J. Richter (adam@yggdrasil.com),
.\" with typesetting help from Daniel Quinlan (quinlan@yggdrasil.com).
.\" and Copyright 2003 Michael Kerrisk (mtk.manpages@gmail.com).
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
.\" USA.
.\"
.\" Modified by David A. Wheeler <dwheeler@dwheeler.com> 2000-11-28.
.\" Applied patch by Terran Melconian, aeb, 2001-12-14.
.\" Modified by Hacksaw <hacksaw@hacksaw.org> 2003-03-13.
.\" Modified by Matt Domsch, 2003-04-09: _init and _fini obsolete
.\" Modified by Michael Kerrisk <mtk.manpages@gmail.com> 2003-05-16.
.\" Modified by Walter Harms: dladdr, dlvsym
.\"
.\" Japanese Version Copyright (c) 1998 NAKANO Takeo all rights reserved.
.\" Translated Sat May 23 1998 by NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Updated & Modified 1999-09-14, NAKANO Takeo
.\" Modified 2000-03-19, HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated 2001-02-16, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2001-12-21, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2002-10-21, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2003-09-01, Kentaro Shirakata <argrath@ub32.org>
.\" Updated 2005-03-15, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2006-01-20, Akihiro MOTOKI
.\"
.\"WORD:	linker			
.\"WORD:	dynamic linking		ưŪ
.\"WORD:	dynamic library		ưŪ饤֥
.\"
.TH DLOPEN 3 2007-06-27 "Linux" "Linux Programmer's Manual"
.SH ̾
dlclose, dlerror, dlopen, dlsym \- ưŪ󥯤Ԥؤ
ץߥ󥰥󥿡ե
.SH 
.B #include <dlfcn.h>
.sp
.BI "void *dlopen(const char *" filename ", int " flag );
.sp
.B "char *dlerror(void);"
.sp
.BI "void *dlsym(void *" handle ", const char *" symbol );
.sp
.BI "int dlclose(void *" handle );
.sp
\fI\-ldl\fP ǥ󥯤롣
.SH 
.BR dlopen (),
.BR dlsym (),
.BR dlclose (),
.BR dlerror ()
 4ĤδؿϡưŪ (dynamic linking) Ԥؤ
󥿥եΤǤ롣
.SS "dlerror()"
ؿ
.BR dlerror ()
ϡ
.BR dlerror ()
ƤӽФ줿ˡ
.BR dlopen (),
.BR dlsym (),
.BR dlclose ()
Τ줫ǺǸȯ顼ˤĤƤå֤
ޤƤӽФ줿ǡ顼ȯƤʤ NULL ֤
.SS "dlopen()"
ؿ
.BR dlopen ()
ϡNULL ü줿ʸ
.I filename
ǻꤵ줿ե̾ưŪ饤֥ (dynamic library) ɤ
ưŪ饤֥ؤ֥ϥɥפ֤
.I filename
 NULL ξ硢ᥤ󡦥ץؤΥϥɥ뤬֤롣
.I filename
å ("/") ޤ硢(ФФ)ѥ̾ȤƲᤵ롣
ʳξ硢ưŪ󥫤ϰʲμǥ饤֥򸡺
(ܺ٤
.BR ld.so (8)
򻲾):
.IP o 4
(ELF Τ) ƤӽФץμ¹ԥե DT_RPATH ޤޤƤꡢ
DT_RUNPATH ޤޤƤʤ硢DT_RPATH ˽񤫤Ƥ
ǥ쥯ȥꡦꥹȤ򸡺롣
.IP o
Ķѿ
.B LD_LIBRARY_PATH
ǻꤵ줿ڤΥǥ쥯ȥꡦꥹȤ򸡺롣
(ƥͳǡѿ set-UID  set-GID 줿
ץξ̵뤵)
.IP o
(ELF Τ) ƤӽФץμ¹ԥե DT_RUNPATH ޤޤ
硢Υ˽񤫤Ƥǥ쥯ȥꡦꥹȤ򸡺롣
.IP o
åե
.I /etc/ld.so.cache

.I filename
Υȥ꤬äƤ뤫å
.RB ( /etc/ld.so.cache

.BR ldconfig (8)
ˤäƴƤ)
.IP o
ǥ쥯ȥ
.I /lib

.I /usr/lib
򤳤ν֤Ǹ롣
.PP
Υ饤֥꤬¾ζͭ饤֥˰¸Ƥϡ
¸Ƥ饤֥ưŪ󥫤Ʊ롼˴Ť
ưŪ˥ɤ (Υ饤֥ˤ˰¸طʤɤ
νϺƵŪ˹Ԥ)
.PP
.I flag
ˤϰʲ 2 ĤͤΤ줫ޤʤФʤʤ:
.TP
.B RTLD_LAZY
lazy binding (ȴʥܥηդ) Ԥ
ܥβϤΥܥ򻲾Ȥ륳ɤ¹ԤȤˤΤ
Ԥ롣ܥ뤬٤⻲ȤʤäˤϡΥܥ
褵ʤޤޤȤʤ롣
(lazy binding ϴؿȤˤĤƤΤ߼»ܤ; ѿؤλȤϾ
饤֥꤬ɤ줿ľ˲褵롣)
.TP
.B RTLD_NOW
ͤꤵ뤫Ķѿ
.B LD_BIND_NOW
˶Ǥʤʸꤵ줿硢
饤֥̤ΥܥƲ褷Ƥ
.BR dlopen ()
롣ǤʤäȤˤϥ顼֤롣
.PP
ʲͤΤ 0 İʾ (OR) η
.I flag
ɲä뤳ȤǤ:
.TP
.B RTLD_GLOBAL
Υ饤֥Ƥ륷ܥ뤬ǥɤ
饤֥ΥܥѤǤ褦ˤʤ롣
.TP
.B RTLD_LOCAL
Υե饰
.B RTLD_GLOBAL
ȿФΰ̣ǤꡢɤΥե饰ꤵʤä
餬ǥեȤȤʤ롣
Υ饤֥Ƥ륷ܥϡǥɤ
饤֥ǤΥܥ뻲ȤѤǤʤ
.TP
.BR RTLD_NODELETE " (glibc 2.2 ʹ)"
.BR dlclose ()
ˤΥ饤֥򥢥ɤʤ
ΤᡢƱ饤֥򤳤ʹߤ
.BR dlopen ()
Ǻ٥ɤˡ饤֥ŪѿϺƽʤ
Υե饰 POSIX.1-2001 ǤϵꤵƤʤ
.\" ( Solaris ¸ߤ)
.TP
.BR RTLD_NOLOAD " (glibc 2.2 ʹ)"
Υ饤֥ɤʤ
Υե饰ϤΥ饤֥꤬ǤȤ߹ޤƤ뤫򸡺Τ
ѤǤ
.RB ( dlopen ()
ϡ饤֥꤬Ȥ߹ޤƤʤ NULL ֤
ǤȤ߹ޤƤФΥ饤֥Υϥɥ֤)
ޤǤ˥ɤƤ饤֥Υե饰򾺳ʤΤˤ
ѤǤ롣㤨С
.B RTLD_LOCAL
ǥɤ饤֥
.BR RTLD_NOLOAD\ |\ RTLD_GLOBAL
Ǻƥץ󤹤뤳ȤǤ롣
Υե饰 POSIX.1-2001 ǤϵꤵƤʤ
.\" ( Solaris ¸ߤ)
.TP
.BR RTLD_DEEPBIND " (glibc 2.3.4 ʹ)"
.\" Inimitably described by UD in
.\" http://sources.redhat.com/ml/libc-hacker/2004-09/msg00083.html.
Υ饤֥Υܥλΰ򥰥Хΰ֤롣
Ĥޤꡢ¢Υ饤֥ǤϡǤ˥ɤ줿饤֥˴ޤޤ
Ʊ̾ΥХʥܥ⼫饤֥Υܥ뤬ͥ褷
Ȥ롣
Υե饰 POSIX.1-2001 ǤϵꤵƤʤ
.PP
.I filename
 NULL ݥ󥿤Ǥϡ
֤ϥɥϥᥤ󡦥ץΤΤˤʤ롣
Υϥɥ뤬
.BR dlsym ()
Ϥȡܥθϡᥤ󡦥ץ⡢
ץεư˥ɤƤζͭ饤֥ꡢ
.BR dlopen ()
ˤä
.B RTLD_GLOBAL
ե饰դǥɤ줿Ƥζͭ饤֥ꡢνǹԤ롣
.PP
ץ󤵤줿饤֥ǤγȤϡ
Υ饤֥ΰ¸ꥹȤˤ饤֥꤫
.B RTLD_GLOBAL
ե饰դǴ˥ץ󤵤Ƥ饤֥ȤäƲ褵롣
¹ԥե뤬 "\-rdynamic" ե饰 ("\-\-export\-dynamic" Ʊ)
դǥ󥯤Ƥϡ¹ԥեΥХ륷ܥ⡢
ưŪ˥ɤ饤֥λȲѤ롣
.PP
Ʊ饤֥꤬
.BR dlopen ()
ˤäƺ٥ɤ줿ˤϡƱեϥɥ뤬֤롣
dl 饤֥ϥ饤֥ϥɥΥ󥯿Ƥ롣
äưŪ饤֥
.BR dlclose ()

.BR dlopen ()
ƱƤӽФʤ¤ꥢɤʤ
.BR _init ()
롼ϰ٤ƤӽФ
.RB ( _init ()
¸ߤΤ)
.B RTLD_NOW
ꤵ
.BR dlopen ()
ƤӽФ줿硢
.B RTLD_LAZY
ǰ˥ɤ줿饤֥Υܥ褬¹Ԥ뤳Ȥ롣
.PP
.BR dlopen ()
ϡ餫ͳǼԤ NULL ֤

.SS "dlsym()"
ؿ
.BR dlsym ()
ϡ
.BR dlopen ()
֤ưŪ饤֥Ρ֥ϥɥפȡ
NULL ü줿ܥ̾ʸ˼ꡢ
Υܥ뤬ɤ줿Υɥ쥹֤
ܥ뤬ꤵ줿饤֥ȡꤵ줿饤֥꤬ɤݤ
.BR dlopen ()
ưŪ˥ɤƥ饤֥Τˤ⸫Ĥʤˤϡ
.BR dlsym ()
 NULL ֤
.RB ( dlsym ()
ˤ븡ϡΥ饤֥ΰ¸طΥĥ꡼Ƭ
éäƹԤ)
ºݤˤϥܥͼΤ NULL ˤʤ뤳Ȥ⤢ (Τᡢ
.BR dlsym ()
֤ͤ NULL ǤäȤƤɬ⥨顼ȤǤϤʤ)
顼ɤǧˡϰʲ̤Ǥ:
.BR dlerror ()
ƤӽФưΥ顼֤򥯥ꥢƤ顢
.BR dlsym ()
ƤӽФθǤ⤦
.BR dlerror ()
ƤӽФơ
.BR dlerror ()
֤ͤѿ¸¸ͤ NULL Ǥ뤫Ƚꤹ롣
.PP
.B RTLD_DEFAULT

.B RTLD_NEXT
ȤĤ̤ʵϥɥ뤬롣
.B RTLD_DEFAULT
ϡǥեȤΥ饤֥긡ˤäơ
оݤΥܥ뤬ǽ˸Ȥõ
.B RTLD_NEXT
ϡ饤֥긡ǸߤΥ饤֥ʹߤǺǽ
ؿȤõεǽȤȤǡ̤ζͭ饤֥
ؿؤΥåѡ󶡤뤳ȤǤ롣
.SS "dlclose()"
ؿ
.BR dlclose ()
ưŪ饤֥Υϥɥ
.I handle
λȥȤ 1 餹ȥȤ 0 ˤʤꡢɤƤ
¾Υ饤֥꤫餽Υ饤֥Υܥ뤬ȤƤʤС
ưŪ饤֥򥢥ɤ롣
.LP
ؿ
.BR dlclose ()
ϡ 0 ֤顼ξ 0 ʳ֤
.SS "ѻߤ줿ܥ _init()  _fini()"
󥫤
.B _init

.B _fini
̤ʥܥȲ᤹롣
ưŪ饤֥
.BR _init ()
Ȥ̾Υ롼󤬥ݡȤƤС
Υɤϡ饤֥Υɸ塢
.BR dlopen ()
˼¹Ԥ롣
ưŪ饤֥
.BR _fini ()
Ȥ̾Υ롼󤬥ݡȤƤС
饤֥꤬ɤľˤΥ롼󤬸ƤӽФ롣
ƥεưեФ󥯤򤱤ɬפ硢
.BR gcc (1)
Υޥɥ饤
.I \-nostartfiles
ץꤹФ褤
.LP
Υ롼䡢gcc Υץ
.B \-nostartfiles

.B \-nostdlib
ϻѤʤȤ侩롣
Ȥȡ˾ޤʤư򤹤뤳Ȥ롣
ʤʤ顢(̤֤Ԥʤ¤)  constructor/destructor
롼ϼ¹ԤʤǤ롣
.\" void _init(void) __attribute__((constructor));
.\" void _fini(void) __attribute__((destructor));
.LP
ˡ饤֥
.B __attribute__((constructor))

.B __attribute__((destructor))
δؿ°Ȥäɬפʥ롼򥨥ݡȤΤ褤
ˤĤƤ gcc  info ڡ򻲾ȤΤȡ
constructor 롼
.BR dlopen ()
˼¹Ԥ졢
destructor 롼
.BR dlclose ()
˼¹Ԥ롣
.SS GNU Ǥγĥ: dladdr()  dlvsym()
glibc Ǥ POSIX ˤϵܤƤʤؿ 2ɲäƤ롣
ץȥפϰʲ̤Ǥ롣
.sp
.nf
.B #define _GNU_SOURCE
.B #include <dlfcn.h>
.sp
.BI "int dladdr(void *" addr ", Dl_info *" info );
.sp
.BI "void *dlvsym(void *" handle ", char *" symbol ", char *" version );
.fi
.PP
ؿ
.BR dladdr ()
ϡؿΥݥ󥿤ˤȤꡢؿ̾ȴؿƤ
եβߤ롣
.I Dl_info
¤Τ˳Ǽ롣
.sp
.in +4n
.nf
typedef struct {
    const char *dli_fname;  /* Filename of defining object */
    void       *dli_fbase;  /* Load address of that object */
    const char *dli_sname;  /* Name of nearest lower symbol */
    void       *dli_saddr;  /* Exact value of nearest symbol */
} Dl_info;
.fi
.in
.sp
.BR dladdr ()
ϡ顼ˤ 0 ֤ 0 ʳ֤
.PP
ؿ
.BR dlvsym ()

.BR dlsym ()
Ʊư򤹤뤬СʸϤ
ɲäƤۤʤ롣
.SH 
POSIX.1-2003 ˤ
.BR dlclose (),
.BR dlerror (),
.BR dlopen (),
.BR dlsym ().
εܤ롣
.SH 
ܥ
.B RTLD_DEFAULT

.B RTLD_NEXT

.I <dlfcn.h>
Ƥꡢ
.I <dlfcn.h>
Υ󥯥롼
.B _GNU_SOURCE
ƤΤͭȤʤ롣
.\" .LP
.\" .BR dlerror ()
.\" ֤ʸѹ٤ǤϤʤƥˤäƤϡ
.\" ʲΤ褦ʥץȥפˤʤäƤ롣
.\" .sp
.\" .in +5
.\" .B "const char *dlerror(void);"
.\" .in

glibc 2.2.3 ʹߤǤϡ
.BR atexit (3)
Ȥäơ饤֥꤬ɤݤ˼ưŪ˸ƤӽФ
λϥɥ (exit handler) Ͽ뤳ȤǤ롣
.SS 
dlopen 󥿡եɸ SunOS ȤˤƤ롣
SunOS ˤ
.BR dladdr ()
⤢ä
.BR dlvsym ()
Ϥʤä
.SH 
math 饤֥ɤ2.0 ;ɽ
.nf

#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

int
main(int argc, char **argv)
{
    void *handle;
    double (*cosine)(double);
    char *error;

    handle = dlopen("libm.so", RTLD_LAZY);
    if (!handle) {
        fprintf(stderr, "%s\en", dlerror());
        exit(EXIT_FAILURE);
    }

    dlerror();    /* Clear any existing error */

    /* Writing: cosine = (double (*)(double)) dlsym(handle, "cos");
       would seem more natural, but the C99 standard leaves
       casting from "void *" to a function pointer undefined.
       The assignment used below is the POSIX.1\-2003 (Technical
       Corrigendum 1) workaround; see the Rationale for the
       POSIX specification of dlsym(). */

    *(void **) (&cosine) = dlsym(handle, "cos");
.\" But in fact "gcc -O2 -Wall" will complain about the preceding cast.

    if ((error = dlerror()) != NULL)  {
        fprintf(stderr, "%s\en", error);
        exit(EXIT_FAILURE);
    }

    printf("%f\en", (*cosine)(2.0));
    dlclose(handle);
    exit(EXIT_SUCCESS);
}
.fi
.PP
Υץ "foo.c" ˽񤤤ȤȡʲΥޥɤǥץ
ӥɤǤ롣
.in +4n
.LP
gcc \-rdynamic \-o foo foo.c \-ldl
.in
.PP
.BR _init ()

.BR _fini ()
򥨥ݡȤ饤֥ξ
ʲΤ褦ˤƥѥ뤹ɬפ롣
Ȥ \fIbar.c\fP 򥳥ѥ뤹:
.in +4n
.LP
gcc \-shared \-nostartfiles \-o bar bar.c
.in
.SH Ϣ
.BR ld (1),
.BR ldd (1),
.BR dl_iterate_phdr (3),
.BR feature_test_macros (7),
.BR ld.so (8),
.BR ldconfig (8),
ld.so info pages, gcc info pages, ld info pages