(split) LDP_man-pages: release ioctl.2 [JM:00378]

[linuxjm/LDP_man-pages.git] / draft / man3 / dlopen.3

.\" -*- 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
.\" Modified by Petr Baudis <pasky@suse.cz>, 2008-12-04: dladdr caveat
.\"
.\" 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
.\" Updated 2009-03-02, Akihiro MOTOKI, LDP v3.19
.\"
.\"WORD:        linker                  ¥ê¥ó¥«
.\"WORD:        dynamic linking         ưŪ¥ê¥ó¥¯
.\"WORD:        dynamic library         ưŪ¥é¥¤¥Ö¥é¥ê
.\"
.TH DLOPEN 3 2008-12-06 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.\"O dlclose, dlerror, dlopen, dlsym \- Programming interface to dynamic linking loader
.SH ̾Á°
dlclose, dlerror, dlopen, dlsym \- ưŪ¥ê¥ó¥¯¤ò¹Ô¤¦¥í¡¼¥À¤Ø¤Î
¥×¥í¥°¥é¥ß¥ó¥°¥¤¥ó¥¿¡¼¥Õ¥§¡¼¥¹
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.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
.\"O Link with \fI\-ldl\fP.
\fI\-ldl\fP ¤Ç¥ê¥ó¥¯¤¹¤ë¡£
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The four functions
.\"O .BR dlopen (),
.\"O .BR dlsym (),
.\"O .BR dlclose (),
.\"O .BR dlerror ()
.\"O implement the interface to the dynamic linking loader.
.BR dlopen (),
.BR dlsym (),
.BR dlclose (),
.BR dlerror ()
¤Î 4¤Ä¤Î´Ø¿ô¤Ï¡¢Æ°Åª¥ê¥ó¥¯ (dynamic linking) ¤ò¹Ô¤¦¥í¡¼¥À¤Ø¤Î
¥¤¥ó¥¿¥Õ¥§¡¼¥¹¤ò¼ÂÁõ¤·¤¿¤â¤Î¤Ç¤¢¤ë¡£
.SS "dlerror()"
.\"O The function
.\"O .BR dlerror ()
.\"O returns a human readable string describing the most recent error
.\"O that occurred from
.\"O .BR dlopen (),
.\"O .BR dlsym ()
.\"O or
.\"O .BR dlclose ()
.\"O since the last call to
.\"O .BR dlerror ().
.\"O It returns NULL if no errors have occurred since initialization or since
.\"O it was last called.
´Ø¿ô
.BR dlerror ()
¤Ï¡¢Á°²ó
.BR dlerror ()
¤¬¸Æ¤Ó½Ð¤µ¤ì¤¿¸å¤Ë¡¢
.BR dlopen (),
.BR dlsym (),
.BR dlclose ()
¤Î¤¤¤º¤ì¤«¤ÇºÇ¸å¤ËȯÀ¸¤·¤¿¥¨¥é¡¼¤Ë¤Ä¤¤¤Æ¤ÎÀâÌÀ¥á¥Ã¥»¡¼¥¸¤òÊÖ¤¹¡£
½é´ü²½¸å¤Þ¤¿¤ÏÁ°²ó¸Æ¤Ó½Ð¤µ¤ì¤¿¸å¤Ç¡¢¥¨¥é¡¼¤¬È¯À¸¤·¤Æ¤¤¤Ê¤±¤ì¤Ð NULL ¤òÊÖ¤¹¡£
.SS "dlopen()"
.\"O The function
.\"O .BR dlopen ()
.\"O loads the dynamic library file named by the null-terminated
.\"O string
.\"O .I filename
.\"O and returns an opaque "handle" for the dynamic library.
´Ø¿ô
.BR dlopen ()
¤Ï¡¢NULL ½ªÃ¼¤µ¤ì¤¿Ê¸»úÎó
.I filename
¤Ç»ØÄꤵ¤ì¤¿¥Õ¥¡¥¤¥ë̾¤ÎưŪ¥é¥¤¥Ö¥é¥ê (dynamic library) ¤ò¥í¡¼¥É¤·¡¢
¤½¤ÎưŪ¥é¥¤¥Ö¥é¥ê¤Ø¤ÎÆâÉô¡Ö¥Ï¥ó¥É¥ë¡×¤òÊÖ¤¹¡£
.\"O If
.\"O .I filename
.\"O is NULL, then the returned handle is for the main program.
.\"O If
.\"O .I filename
.\"O contains a slash ("/"), then it is interpreted as a (relative
.\"O or absolute) pathname.
.I filename
¤¬ NULL ¤Î¾ì¹ç¡¢¥á¥¤¥ó¡¦¥×¥í¥°¥é¥à¤Ø¤Î¥Ï¥ó¥É¥ë¤¬ÊÖ¤µ¤ì¤ë¡£
.I filename
¤¬¥¹¥é¥Ã¥·¥å ("/") ¤ò´Þ¤à¾ì¹ç¡¢(ÁêÂФ«ÀäÂФ«¤Î)¥Ñ¥¹Ì¾¤È¤·¤Æ²ò¼á¤µ¤ì¤ë¡£
.\"O Otherwise, the dynamic linker searches for the library as follows
.\"O (see
.\"O .BR ld.so (8)
.\"O for further details):
¤½¤ì°Ê³°¤Î¾ì¹ç¡¢Æ°Åª¥ê¥ó¥«¤Ï°Ê²¼¤Î¼ê½ç¤Ç¥é¥¤¥Ö¥é¥ê¤ò¸¡º÷¤¹¤ë
(¾ÜºÙ¤Ï
.BR ld.so (8)
¤ò»²¾È):
.IP o 4
.\"O (ELF only) If the executable file for the calling program
.\"O contains a DT_RPATH tag, and does not contain a DT_RUNPATH tag,
.\"O then the directories listed in the DT_RPATH tag are searched.
(ELF ¤Î¤ß) ¸Æ¤Ó½Ð¤·¸µ¥×¥í¥°¥é¥à¤Î¼Â¹Ô¥Õ¥¡¥¤¥ë¤Ë DT_RPATH ¥¿¥°¤¬´Þ¤Þ¤ì¤Æ¤ª¤ê¡¢
DT_RUNPATH ¥¿¥°¤¬´Þ¤Þ¤ì¤Æ¤¤¤Ê¤¤¾ì¹ç¡¢DT_RPATH ¥¿¥°¤Ë½ñ¤«¤ì¤Æ¤¤¤ë
¥Ç¥£¥ì¥¯¥È¥ê¡¦¥ê¥¹¥È¤ò¸¡º÷¤¹¤ë¡£
.IP o
.\"O If, at the time that the program was started, the environment variable
.\"O .B LD_LIBRARY_PATH
.\"O was defined to contain a colon-separated list of directories,
.\"O then these are searched.
.\"O (As a security measure this variable is ignored for set-user-ID and
.\"O set-group-ID programs.)
¥×¥í¥°¥é¥à¤Î³«»Ï»þ¤Ë´Ä¶­ÊÑ¿ô
.B LD_LIBRARY_PATH
¤Ë¥³¥í¥ó¶èÀÚ¤ê¤Î¥Ç¥£¥ì¥¯¥È¥ê¤Î¥ê¥¹¥È¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ì¤Ð¡¢
¤³¤Î´Ä¶­ÊÑ¿ô¤ËÄêµÁ¤µ¤ì¤¿¥Ç¥£¥ì¥¯¥È¥ê¤¬¸¡º÷¤µ¤ì¤ë
(¥»¥­¥å¥ê¥Æ¥£¾å¤ÎÍýͳ¤Ç¡¢¤³¤ÎÊÑ¿ô¤Ï set-UID ¤ä set-GID ¤µ¤ì¤¿
¥×¥í¥°¥é¥à¤Î¾ì¹ç¤Ï̵»ë¤µ¤ì¤ë)¡£
.IP o
.\"O (ELF only) If the executable file for the calling program
.\"O contains a DT_RUNPATH tag, then the directories listed in that tag
.\"O are searched.
(ELF ¤Î¤ß) ¸Æ¤Ó½Ð¤·¸µ¥×¥í¥°¥é¥à¤Î¼Â¹Ô¥Õ¥¡¥¤¥ë¤Ë DT_RUNPATH ¥¿¥°¤¬´Þ¤Þ¤ì¤Æ
¤¤¤ë¾ì¹ç¡¢¤½¤Î¥¿¥°¤Ë½ñ¤«¤ì¤Æ¤¤¤ë¥Ç¥£¥ì¥¯¥È¥ê¡¦¥ê¥¹¥È¤ò¸¡º÷¤¹¤ë¡£
.IP o
.\"O The cache file
.\"O .I /etc/ld.so.cache
.\"O (maintained by
.\"O .BR ldconfig (8))
.\"O is checked to see whether it contains an entry for
.\"O .IR filename .
¥­¥ã¥Ã¥·¥å¥Õ¥¡¥¤¥ë
.I /etc/ld.so.cache
¤ÎÃæ¤Ë
.I filename
¤Î¥¨¥ó¥È¥ê¤¬Æþ¤Ã¤Æ¤¤¤ë¤«¤ò¥Á¥§¥Ã¥¯¤¹¤ë
.RB ( /etc/ld.so.cache
¤Ï
.BR ldconfig (8)
¤Ë¤è¤Ã¤Æ´ÉÍý¤µ¤ì¤Æ¤¤¤ë)¡£
.IP o
.\"O The directories
.\"O .I /lib
.\"O and
.\"O .I /usr/lib
.\"O are searched (in that order).
¥Ç¥£¥ì¥¯¥È¥ê
.I /lib
¤È
.I /usr/lib
¤ò¤³¤Î½çÈ֤Ǹ¡º÷¤¹¤ë¡£
.PP
.\"O If the library has dependencies on other shared libraries,
.\"O then these are also automatically loaded by the dynamic linker
.\"O using the same rules.
.\"O (This process may occur recursively,
.\"O if those libraries in turn have dependencies, and so on.)
¤½¤Î¥é¥¤¥Ö¥é¥ê¤¬Â¾¤Î¶¦Í­¥é¥¤¥Ö¥é¥ê¤Ë°Í¸¤·¤Æ¤¤¤ë¾ì¹ç¤Ï¡¢
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¤³¤Î½èÍý¤ÏºÆµ¢Åª¤Ë¹Ô¤ï¤ì¤ë)¡£
.PP
.\"O One of the following two values must be included in
.\"O .IR flag :
.I flag
¤Ë¤Ï°Ê²¼¤Î 2 ¤Ä¤ÎÃͤΤ¤¤º¤ì¤«¤ò´Þ¤á¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤:
.TP
.B RTLD_LAZY
.\"O Perform lazy binding.
.\"O Only resolve symbols as the code that references them is executed.
.\"O If the symbol is never referenced, then it is never resolved.
.\"O (Lazy binding is only performed for function references;
.\"O references to variables are always immediately bound when
.\"O the library is loaded.)
lazy binding (¼êÈ´¤­¤Ê¥·¥ó¥Ü¥ë¤Î·ë¤ÓÉÕ¤±) ¤¬¹Ô¤¦¡£
¥·¥ó¥Ü¥ë¤Î²ò·è¤Ï¤½¤Î¥·¥ó¥Ü¥ë¤ò»²¾È¤¹¤ë¥³¡¼¥É¤¬¼Â¹Ô¤µ¤ì¤ë¤È¤­¤Ë¤Î¤ß
¹Ô¤ï¤ì¤ë¡£¥·¥ó¥Ü¥ë¤¬°ìÅ٤⻲¾È¤µ¤ì¤Ê¤«¤Ã¤¿¾ì¹ç¤Ë¤Ï¡¢¤½¤Î¥·¥ó¥Ü¥ë¤Ï
²ò·è¤µ¤ì¤Ê¤¤¤Þ¤Þ¤È¤Ê¤ë¡£
(lazy binding ¤Ï´Ø¿ô»²¾È¤Ë¤Ä¤¤¤Æ¤Î¤ß¼Â»Ü¤µ¤ì¤ë; ÊÑ¿ô¤Ø¤Î»²¾È¤Ï¾ï¤Ë
¥é¥¤¥Ö¥é¥ê¤¬¥í¡¼¥É¤µ¤ì¤¿»þÅÀ¤Çľ¤Á¤Ë²ò·è¤µ¤ì¤ë¡£)
.TP
.B RTLD_NOW
.\"O If this value is specified, or the environment variable
.\"O .B LD_BIND_NOW
.\"O is set to a nonempty string,
.\"O all undefined symbols in the library are resolved before
.\"O .BR dlopen ()
.\"O returns.
.\"O If this cannot be done, an error is returned.
¤³¤ÎÃͤ¬»ØÄꤵ¤ì¤ë¤«¡¢´Ä¶­ÊÑ¿ô
.B LD_BIND_NOW
¤Ë¶õ¤Ç¤Ê¤¤Ê¸»úÎó¤¬ÀßÄꤵ¤ì¤¿¾ì¹ç¡¢
¥é¥¤¥Ö¥é¥êÃæ¤Î̤ÄêµÁ¤Î¥·¥ó¥Ü¥ë¤òÁ´¤Æ²ò·è¤·¤Æ¤«¤é
.BR dlopen ()
¤ÏÉüµ¢¤¹¤ë¡£²ò·è¤Ç¤­¤Ê¤«¤Ã¤¿¤È¤­¤Ë¤Ï¥¨¥é¡¼¤¬ÊÖ¤µ¤ì¤ë¡£
.PP
.\"O Zero or more of the following values may also be ORed in
.\"O .IR flag :
°Ê²¼¤ÎÃͤΤ¦¤Á 0 ¸Ä°Ê¾å¤òÏÀÍýÏ (OR) ¤Î·Á¤Ç
.I flag
¤ËÄɲ乤뤳¤È¤â¤Ç¤­¤ë:
.TP
.B RTLD_GLOBAL
.\"O The symbols defined by this library will be
.\"O made available for symbol resolution of subsequently loaded libraries.
¤³¤Î¥é¥¤¥Ö¥é¥ê¤ÇÄêµÁ¤µ¤ì¤Æ¤¤¤ë¥·¥ó¥Ü¥ë¤¬¡¢¤³¤ì¤è¤ê¸å¤Ç¥í¡¼¥É¤µ¤ì¤ë
¥é¥¤¥Ö¥é¥ê¤Î¥·¥ó¥Ü¥ë²ò·è¤ÇÍøÍѤǤ­¤ë¤è¤¦¤Ë¤Ê¤ë¡£
.TP
.B RTLD_LOCAL
.\"O This is the converse of
.\"O .BR RTLD_GLOBAL ,
.\"O and the default if neither flag is specified.
.\"O Symbols defined in this library are not made available to resolve
.\"O references in subsequently loaded libraries.
¤³¤Î¥Õ¥é¥°¤Ï
.B RTLD_GLOBAL
¤ÎÈ¿ÂФΰÕÌ£¤Ç¤¢¤ê¡¢¤É¤Á¤é¤Î¥Õ¥é¥°¤â»ØÄꤵ¤ì¤Ê¤«¤Ã¤¿¾ì¹ç¤Ï
¤³¤Á¤é¤¬¥Ç¥Õ¥©¥ë¥È¤È¤Ê¤ë¡£
¤³¤Î¥é¥¤¥Ö¥é¥ê¤ÇÄêµÁ¤µ¤ì¤Æ¤¤¤ë¥·¥ó¥Ü¥ë¤Ï¡¢¤³¤ì¤è¤ê¸å¤Ç¥í¡¼¥É¤µ¤ì¤ë
¥é¥¤¥Ö¥é¥ê¤Ç¤Î¥·¥ó¥Ü¥ë»²¾È¤ÇÍøÍѤǤ­¤Ê¤¤¡£
.TP
.\"O .BR RTLD_NODELETE " (since glibc 2.2)"
.BR RTLD_NODELETE " (glibc 2.2 °Ê¹ß)"
.\"O Do not unload the library during
.\"O .BR dlclose ().
.\"O Consequently, the library's static variables are not reinitialized
.\"O if the library is reloaded with
.\"O .BR dlopen ()
.\"O at a later time.
.\"O This flag is not specified in POSIX.1-2001.
.\"O .\" (But it is present on Solaris.)
.BR dlclose ()
Ãæ¤Ë¤½¤Î¥é¥¤¥Ö¥é¥ê¤ò¥¢¥ó¥í¡¼¥É¤·¤Ê¤¤¡£
¤½¤Î¤¿¤á¡¢Æ±¤¸¥é¥¤¥Ö¥é¥ê¤ò¤³¤ì°Ê¹ß¤Ë
.BR dlopen ()
¤ÇºÆÅÙ¥í¡¼¥É¤·¤¿¾ì¹ç¤Ë¡¢¥é¥¤¥Ö¥é¥êÆâ¤ÎÀÅŪÊÑ¿ô¤ÏºÆ½é´ü²½¤µ¤ì¤Ê¤¤¡£
¤³¤Î¥Õ¥é¥°¤Ï POSIX.1-2001 ¤Ç¤Ïµ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤¡£
.\" (¤·¤«¤· Solaris ¤Ë¸ºß¤¹¤ë)
.TP
.\"O .BR RTLD_NOLOAD " (since glibc 2.2)"
.BR RTLD_NOLOAD " (glibc 2.2 °Ê¹ß)"
.\"O Don't load the library.
.\"O This can be used to test if the library is already resident
.\"O .RB ( dlopen ()
.\"O returns NULL if it is not, or the library's handle if it is resident).
.\"O This flag can also be used to promote the flags on a library
.\"O that is already loaded.
.\"O For example, a library that was previously loaded with
.\"O .B RTLD_LOCAL
.\"O can be reopened with
.\"O .BR RTLD_NOLOAD\ |\ RTLD_GLOBAL .
.\"O This flag is not specified in POSIX.1-2001.
.\"O .\" (But it is present on Solaris.)
.\"O .\"
¤½¤Î¥é¥¤¥Ö¥é¥ê¤ò¥í¡¼¥É¤·¤Ê¤¤¡£
¤³¤Î¥Õ¥é¥°¤Ï¤½¤Î¥é¥¤¥Ö¥é¥ê¤¬¤¹¤Ç¤ËÁȤ߹þ¤Þ¤ì¤Æ¤¤¤ë¤«¤ò¸¡ºº¤¹¤ë¤Î¤Ë
ÍøÍѤǤ­¤ë
.RB ( dlopen ()
¤Ï¡¢¥é¥¤¥Ö¥é¥ê¤¬ÁȤ߹þ¤Þ¤ì¤Æ¤¤¤Ê¤±¤ì¤Ð NULL ¤òÊÖ¤·¡¢
¤¹¤Ç¤ËÁȤ߹þ¤Þ¤ì¤Æ¤¤¤ì¤Ð¤½¤Î¥é¥¤¥Ö¥é¥ê¤Î¥Ï¥ó¥É¥ë¤òÊÖ¤¹)¡£
¤Þ¤¿¡¢¤¹¤Ç¤Ë¥í¡¼¥É¤µ¤ì¤Æ¤¤¤ë¥é¥¤¥Ö¥é¥ê¤Î¥Õ¥é¥°¤ò¾º³Ê¤µ¤»¤ë¤Î¤Ë¤â
ÍøÍѤǤ­¤ë¡£Î㤨¤Ð¡¢²áµî¤Ë
.B RTLD_LOCAL
¤Ç¥í¡¼¥É¤·¤¿¥é¥¤¥Ö¥é¥ê¤ò
.BR RTLD_NOLOAD\ |\ RTLD_GLOBAL
¤ÇºÆ¥ª¡¼¥×¥ó¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
¤³¤Î¥Õ¥é¥°¤Ï POSIX.1-2001 ¤Ç¤Ïµ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤¡£
.\" (¤·¤«¤· Solaris ¤Ë¸ºß¤¹¤ë)
.TP
.\"O .BR RTLD_DEEPBIND " (since glibc 2.3.4)"
.BR RTLD_DEEPBIND " (glibc 2.3.4 °Ê¹ß)"
.\" Inimitably described by UD in
.\" http://sources.redhat.com/ml/libc-hacker/2004-09/msg00083.html.
.\"O Place the lookup scope of the symbols in this
.\"O library ahead of the global scope.
.\"O This means that a self-contained library will use
.\"O its own symbols in preference to global symbols with the same name
.\"O contained in libraries that have already been loaded.
.\"O This flag is not specified in POSIX.1-2001.
¤³¤Î¥é¥¤¥Ö¥é¥êÆâ¤Î¥·¥ó¥Ü¥ë¤Î»²¾ÈÎΰè¤ò¥°¥í¡¼¥Ð¥ëÎΰè¤è¤ê¤âÁ°¤ËÇÛÃÖ¤¹¤ë¡£
¤Ä¤Þ¤ê¡¢Æ⢷¿¤Î¥é¥¤¥Ö¥é¥ê¤Ç¤Ï¡¢¤¹¤Ç¤Ë¥í¡¼¥É¤µ¤ì¤¿¥é¥¤¥Ö¥é¥ê¤Ë´Þ¤Þ¤ì¤ë
Ʊ¤¸Ì¾Á°¤Î¥°¥í¡¼¥Ð¥ë¤Ê¥·¥ó¥Ü¥ë¤è¤ê¤â¼«¥é¥¤¥Ö¥é¥êÆâ¤Î¥·¥ó¥Ü¥ë¤¬Í¥À褷¤Æ
»È¤ï¤ì¤ë¡£
¤³¤Î¥Õ¥é¥°¤Ï POSIX.1-2001 ¤Ç¤Ïµ¬Äꤵ¤ì¤Æ¤¤¤Ê¤¤¡£
.PP
.\"O If
.\"O .I filename
.\"O is a NULL pointer, then the returned handle is for the main program.
.I filename
¤¬ NULL ¥Ý¥¤¥ó¥¿¤Ç¤¢¤ë¾ì¹ç¤Ï¡¢
ÊÖ¤µ¤ì¤ë¥Ï¥ó¥É¥ë¤Ï¥á¥¤¥ó¡¦¥×¥í¥°¥é¥à¤Î¤â¤Î¤Ë¤Ê¤ë¡£
.\"O When given to
.\"O .BR dlsym (),
.\"O this handle causes a search for a symbol in the main program,
.\"O followed by all shared libraries loaded at program startup,
.\"O and then all shared libraries loaded by
.\"O .BR dlopen ()
.\"O with the flag
.\"O .BR RTLD_GLOBAL .
¤³¤Î¥Ï¥ó¥É¥ë¤¬
.BR dlsym ()
¤ËÅϤµ¤ì¤ë¤È¡¢¥·¥ó¥Ü¥ë¤Î¸¡º÷¤Ï¡¢¥á¥¤¥ó¡¦¥×¥í¥°¥é¥àÆâ¡¢
¥×¥í¥°¥é¥à¤Îµ¯Æ°»þ¤Ë¥í¡¼¥É¤µ¤ì¤ëÁ´¤Æ¤Î¶¦Í­¥é¥¤¥Ö¥é¥ê¡¢
.BR dlopen ()
¤Ë¤è¤Ã¤Æ
.B RTLD_GLOBAL
¥Õ¥é¥°ÉÕ¤­¤Ç¥í¡¼¥É¤µ¤ì¤¿Á´¤Æ¤Î¶¦Í­¥é¥¤¥Ö¥é¥ê¡¢¤Î½ç½ø¤Ç¹Ô¤ï¤ì¤ë¡£
.PP
.\"O External references in the library are resolved using the libraries
.\"O in that library's dependency list and any other libraries previously
.\"O opened with the
.\"O .B RTLD_GLOBAL
.\"O flag.
.\"O If the executable was linked with the flag "\-rdynamic"
.\"O (or, synonymously, "\-\-export\-dynamic"),
.\"O then the global symbols in the executable will also be used
.\"O to resolve references in a dynamically loaded library.
¥ª¡¼¥×¥ó¤µ¤ì¤¿¥é¥¤¥Ö¥é¥êÃæ¤Ç¤Î³°Éô»²¾È¤Ï¡¢
¤½¤Î¥é¥¤¥Ö¥é¥ê¤Î°Í¸¥ê¥¹¥È¤Ë¤¢¤ë¥é¥¤¥Ö¥é¥ê¤«¡¢
.B RTLD_GLOBAL
¥Õ¥é¥°ÉÕ¤­¤Ç´û¤Ë¥ª¡¼¥×¥ó¤µ¤ì¤Æ¤¤¤ë¥é¥¤¥Ö¥é¥ê¤ò»È¤Ã¤Æ²ò·è¤µ¤ì¤ë¡£
¼Â¹Ô¥Õ¥¡¥¤¥ë¤¬ "\-rdynamic" ¥Õ¥é¥° ("\-\-export\-dynamic" ¤âƱµÁ)
ÉÕ¤­¤Ç¥ê¥ó¥¯¤µ¤ì¤Æ¤¤¤ë¾ì¹ç¤Ï¡¢¼Â¹Ô¥Õ¥¡¥¤¥ëÃæ¤Î¥°¥í¡¼¥Ð¥ë¥·¥ó¥Ü¥ë¤â¡¢
ưŪ¤Ë¥í¡¼¥É¤µ¤ì¤ë¥é¥¤¥Ö¥é¥êÆâ¤Î»²¾È²ò·è¤ËÍѤ¤¤é¤ì¤ë¡£
.PP
.\"O If the same library is loaded again with
.\"O .BR dlopen (),
.\"O the same file handle is returned.
.\"O The dl library maintains reference
.\"O counts for library handles, so a dynamic library is not
.\"O deallocated until
.\"O .BR dlclose ()
.\"O has been called on it as many times as
.\"O .BR dlopen ()
.\"O has succeeded on it.
.\"O The
.\"O .BR _init ()
.\"O routine, if present, is only called once.
.\"O But a subsequent call with
.\"O .B RTLD_NOW
.\"O may force symbol resolution for a library earlier loaded with
.\"O .BR RTLD_LAZY .
Ʊ¤¸¥é¥¤¥Ö¥é¥ê¤¬
.BR dlopen ()
¤Ë¤è¤Ã¤ÆºÆÅÙ¥í¡¼¥É¤µ¤ì¤¿¾ì¹ç¤Ë¤Ï¡¢Æ±¤¸¥Õ¥¡¥¤¥ë¥Ï¥ó¥É¥ë¤¬ÊÖ¤µ¤ì¤ë¡£
dl ¥é¥¤¥Ö¥é¥ê¤Ï¥é¥¤¥Ö¥é¥ê¥Ï¥ó¥É¥ë¤Î¥ê¥ó¥¯¿ô¤ò´ÉÍý¤·¤Æ¤¤¤ë¡£
¤·¤¿¤¬¤Ã¤ÆưŪ¥é¥¤¥Ö¥é¥ê¤Ï
.BR dlclose ()
¤¬
.BR dlopen ()
¤ÈƱ¤¸²ó¿ô¤À¤±¸Æ¤Ó½Ð¤µ¤ì¤Ê¤¤¸Â¤ê¥¢¥ó¥í¡¼¥É¤µ¤ì¤Ê¤¤¡£
.BR _init ()
¥ë¡¼¥Á¥ó¤Ï°ìÅÙ¤À¤±¸Æ¤Ó½Ð¤µ¤ì¤ë
.RB ( _init ()
¤¬Â¸ºß¤¹¤ë¾ì¹ç¤Î¤ß)¡£
.B RTLD_NOW
¤¬»ØÄꤵ¤ì¤Æ
.BR dlopen ()
¤¬¸Æ¤Ó½Ð¤µ¤ì¤¿¾ì¹ç¡¢
.B RTLD_LAZY
¤Ç°ÊÁ°¤Ë¥í¡¼¥É¤µ¤ì¤¿¥é¥¤¥Ö¥é¥ê¤Î¥·¥ó¥Ü¥ë²ò·è¤¬¼Â¹Ô¤µ¤ì¤ë¤³¤È¤¬¤¢¤ë¡£
.PP
.\"O If
.\"O .BR dlopen ()
.\"O fails for any reason, it returns NULL.
.BR dlopen ()
¤Ï¡¢²¿¤é¤«¤ÎÍýͳ¤Ç¼ºÇÔ¤¹¤ë¤È NULL ¤òÊÖ¤¹¡£

.SS "dlsym()"
.\"O The function
.\"O .BR dlsym ()
.\"O takes a "handle" of a dynamic library returned by
.\"O .BR dlopen ()
.\"O and the
.\"O null-terminated symbol name, returning the address where that symbol is
.\"O loaded into memory.
.\"O If the symbol is not found, in the specified
.\"O library or any of the libraries that were automatically loaded by
.\"O .BR dlopen ()
.\"O when that library was loaded,
.\"O .BR dlsym ()
.\"O returns NULL.
´Ø¿ô
.BR dlsym ()
¤Ï¡¢
.BR dlopen ()
¤¬ÊÖ¤·¤¿Æ°Åª¥é¥¤¥Ö¥é¥ê¤Î¡Ö¥Ï¥ó¥É¥ë¡×¤È¡¢
NULL ½ªÃ¼¤µ¤ì¤¿¥·¥ó¥Ü¥ë̾¤Îʸ»úÎó¤ò°ú¤­¿ô¤Ë¼è¤ê¡¢
¤½¤Î¥·¥ó¥Ü¥ë¤¬¥í¡¼¥É¤µ¤ì¤¿¥á¥â¥ê¤Î¥¢¥É¥ì¥¹¤òÊÖ¤¹¡£
¥·¥ó¥Ü¥ë¤¬¡¢»ØÄꤵ¤ì¤¿¥é¥¤¥Ö¥é¥ê¤È¡¢»ØÄꤵ¤ì¤¿¥é¥¤¥Ö¥é¥ê¤¬¥í¡¼¥É¤µ¤ì¤ëºÝ¤Ë
.BR dlopen ()
¤¬¼«Æ°Åª¤Ë¥í¡¼¥É¤·¤Æ¥é¥¤¥Ö¥é¥ê¤Î¤¤¤º¤ì¤Ë¤â¸«¤Ä¤«¤é¤Ê¤¤¾ì¹ç¤Ë¤Ï¡¢
.BR dlsym ()
¤Ï NULL ¤òÊÖ¤¹
.\"O (The search performed by
.\"O .BR dlsym ()
.\"O is breadth first through the dependency tree of these libraries.)
.RB ( dlsym ()
¤Ë¤è¤ë¸¡º÷¤Ï¡¢¤³¤ì¤é¤Î¥é¥¤¥Ö¥é¥ê¤Î°Í¸´Ø·¸¤Î¥Ä¥ê¡¼¤òÀèƬ¤«¤é
é¤Ã¤Æ¹Ô¤ï¤ì¤ë)¡£
.\"O Since the value of the symbol could actually be NULL (so that a
.\"O NULL return from
.\"O .BR dlsym ()
.\"O need not indicate an error), the correct way to test for an error
.\"O is to call
.\"O .BR dlerror ()
.\"O to clear any old error conditions, then call
.\"O .BR dlsym (),
.\"O and then call
.\"O .BR dlerror ()
.\"O again, saving its return value into a variable, and check whether
.\"O this saved value is not NULL.
¼ÂºÝ¤Ë¤Ï¥·¥ó¥Ü¥ë¤ÎÃͼ«ÂΤ¬ NULL ¤Ë¤Ê¤ë¤³¤È¤â¤¢¤ë (¤½¤Î¤¿¤á¡¢
.BR dlsym ()
¤ÎÊÖ¤êÃͤ¬ NULL ¤Ç¤¢¤Ã¤¿¤È¤·¤Æ¤âɬ¤º¤·¤â¥¨¥é¡¼¤È¤¤¤¦Ìõ¤Ç¤Ï¤Ê¤¤)¡£
¥¨¥é¡¼¤«¤É¤¦¤«¤ò³Îǧ¤¹¤ëÀµ¤·¤¤ÊýË¡¤Ï°Ê²¼¤ÎÄ̤ê¤Ç¤¢¤ë:
.BR dlerror ()
¤ò¸Æ¤Ó½Ð¤·¤Æ°ÊÁ°¤Î¥¨¥é¡¼¾õÂÖ¤ò¥¯¥ê¥¢¤·¤Æ¤«¤é¡¢
.BR dlsym ()
¤ò¸Æ¤Ó½Ð¤¹¡£¤½¤Î¸å¤Ç¤â¤¦°ìÅÙ
.BR dlerror ()
¤ò¸Æ¤Ó½Ð¤·¤Æ¡¢
.BR dlerror ()
¤ÎÊÖ¤êÃͤòÊÑ¿ô¤ËÊݸ¤·¡¢Êݸ¤·¤¿Ãͤ¬ NULL ¤Ç¤¢¤ë¤«È½Äꤹ¤ë¡£
.PP
.\"O There are two special pseudo-handles,
.\"O .B RTLD_DEFAULT
.\"O and
.\"O .BR RTLD_NEXT .
.B RTLD_DEFAULT
¤È
.B RTLD_NEXT
¤È¤¤¤¦Æó¤Ä¤ÎÆÃÊ̤ʵ¼»÷¥Ï¥ó¥É¥ë¤¬¤¢¤ë¡£
.\"O The former will find the first occurrence of the desired symbol
.\"O using the default library search order.
.\"O The latter
.\"O will find the next occurrence of a function in the search order
.\"O after the current library.
.\"O This allows one to provide a wrapper
.\"O around a function in another shared library.
.B RTLD_DEFAULT
¤Ï¡¢¥Ç¥Õ¥©¥ë¥È¤Î¥é¥¤¥Ö¥é¥ê¸¡º÷½ç½ø¤Ë¤·¤¿¤¬¤Ã¤Æ¡¢
¸¡º÷ÂоݤΥ·¥ó¥Ü¥ë¤¬ºÇ½é¤Ë¸½¤ì¤ë¤È¤³¤í¤òõ¤¹¡£
.B RTLD_NEXT
¤Ï¡¢¥é¥¤¥Ö¥é¥ê¸¡º÷½ç½ø¤ÎÃæ¤Ç¸½ºß¤Î¥é¥¤¥Ö¥é¥ê°Ê¹ß¤ÇºÇ½é¤Ë
´Ø¿ô¤¬¸½¤ì¤ë¤È¤³¤í¤òõ¤¹¡£¤³¤Îµ¡Ç½¤ò»È¤¦¤³¤È¤Ç¡¢Ê̤ζ¦Í­¥é¥¤¥Ö¥é¥ê¤Î
´Ø¿ô¤Ø¤Î¥é¥Ã¥Ñ¡¼¤òÄ󶡤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
.SS "dlclose()"
.\"O The function
.\"O .BR dlclose ()
.\"O decrements the reference count on the dynamic library handle
.\"O .IR handle .
.\"O If the reference count drops to zero and no other loaded libraries use
.\"O symbols in it, then the dynamic library is unloaded.
´Ø¿ô
.BR dlclose ()
¤ÏưŪ¥é¥¤¥Ö¥é¥ê¤Î¥Ï¥ó¥É¥ë
.I handle
¤Î»²¾È¥«¥¦¥ó¥È¤ò 1 ¸º¤é¤¹¡£»²¾È¥«¥¦¥ó¥È¤¬ 0 ¤Ë¤Ê¤ê¡¢¥í¡¼¥É¤µ¤ì¤Æ¤¤¤ë
¾¤Î¥é¥¤¥Ö¥é¥ê¤«¤é¤½¤Î¥é¥¤¥Ö¥é¥êÆâ¤Î¥·¥ó¥Ü¥ë¤¬»È¤ï¤ì¤Æ¤¤¤Ê¤±¤ì¤Ð¡¢
¤½¤ÎưŪ¥é¥¤¥Ö¥é¥ê¤ò¥¢¥ó¥í¡¼¥É¤¹¤ë¡£
.LP
.\"O The function
.\"O .BR dlclose ()
.\"O returns 0 on success, and nonzero on error.
´Ø¿ô
.BR dlclose ()
¤Ï¡¢À®¸ù¤·¤¿¾ì¹ç¤Ï 0 ¤òÊÖ¤·¡¢¥¨¥é¡¼¤Î¾ì¹ç 0 °Ê³°¤òÊÖ¤¹¡£
.\"O .SS "The obsolete symbols _init(0 and _fini()"
.SS "Çѻߤµ¤ì¤¿¥·¥ó¥Ü¥ë _init() ¤È _fini()"
.\"O The linker recognizes special symbols
.\"O .B _init
.\"O and
.\"O .BR _fini .
.\"O If a dynamic library exports a routine named
.\"O .BR _init (),
.\"O then that code is executed after the loading, before
.\"O .BR dlopen ()
.\"O returns.
.\"O If the dynamic library exports a routine named
.\"O .BR _fini (),
.\"O then that routine is called just before the library is unloaded.
¥ê¥ó¥«¤Ï
.B _init
¤È
.B _fini
¤òÆÃÊ̤ʥ·¥ó¥Ü¥ë¤È²ò¼á¤¹¤ë¡£
¤¢¤ëưŪ¥é¥¤¥Ö¥é¥ê¤Ç
.BR _init ()
¤È¤¤¤¦Ì¾Á°¤Î¥ë¡¼¥Á¥ó¤¬¥¨¥¯¥¹¥Ý¡¼¥È¤µ¤ì¤Æ¤¤¤ì¤Ð¡¢
¤½¤Î¥³¡¼¥É¤Ï¡¢¥é¥¤¥Ö¥é¥ê¤Î¥í¡¼¥É¸å¡¢¤«¤Ä
.BR dlopen ()
¤¬Éüµ¢¤¹¤ëÁ°¤Ë¼Â¹Ô¤µ¤ì¤ë¡£
¤½¤ÎưŪ¥é¥¤¥Ö¥é¥ê¤Ç
.BR _fini ()
¤È¤¤¤¦Ì¾Á°¤Î¥ë¡¼¥Á¥ó¤¬¥¨¥¯¥¹¥Ý¡¼¥È¤µ¤ì¤Æ¤¤¤ì¤Ð¡¢
¥é¥¤¥Ö¥é¥ê¤¬¥¢¥ó¥í¡¼¥É¤µ¤ì¤ëľÁ°¤Ë¤½¤Î¥ë¡¼¥Á¥ó¤¬¸Æ¤Ó½Ð¤µ¤ì¤ë¡£
.\"O In case you need to avoid linking against the system startup files,
.\"O this can be done by using the
.\"O .BR gcc (1)
.\"O .I \-nostartfiles
.\"O command-line option.
¥·¥¹¥Æ¥à¤Îµ¯Æ°¥Õ¥¡¥¤¥ë¤ËÂФ¹¤ë¥ê¥ó¥¯¤òÈò¤±¤ëɬÍפ¬¤¢¤ë¾ì¹ç¡¢
.BR gcc (1)
¤Î¥³¥Þ¥ó¥É¥é¥¤¥ó¤Ë
.I \-nostartfiles
¥ª¥×¥·¥ç¥ó¤ò»ØÄꤹ¤ì¤Ð¤è¤¤¡£
.LP
.\"O Using these routines, or the gcc
.\"O .B \-nostartfiles
.\"O or
.\"O .B \-nostdlib
.\"O options, is not recommended.
.\"O Their use may result in undesired behavior,
.\"O since the constructor/destructor routines will not be executed
.\"O (unless special measures are taken).
.\"O .\" void _init(void) __attribute__((constructor));
.\"O .\" void _fini(void) __attribute__((destructor));
¤³¤Î¥ë¡¼¥Á¥ó¤ä¡¢gcc ¤Î¥ª¥×¥·¥ç¥ó
.B \-nostartfiles
¤ä
.B \-nostdlib
¤Ï»ÈÍѤ·¤Ê¤¤¤³¤È¤ò¿ä¾©¤¹¤ë¡£
¤³¤ì¤é¤ò»È¤¦¤È¡¢Ë¾¤Þ¤·¤¯¤Ê¤¤Æ°ºî¤ò¤¹¤ë¤³¤È¤¬¤¢¤ë¡£
¤Ê¤¼¤Ê¤é¡¢(ÆÃÊ̤ÊÁ¼ÃÖ¤¬¹Ô¤ï¤ì¤Ê¤¤¸Â¤ê) ¤³¤ì¤é¤Î constructor/destructor
¥ë¡¼¥Á¥ó¤Ï¼Â¹Ô¤µ¤ì¤Ê¤¤¤«¤é¤Ç¤¢¤ë¡£
.\" void _init(void) __attribute__((constructor));
.\" void _fini(void) __attribute__((destructor));
.LP
.\"O Instead, libraries should export routines using the
.\"O .B __attribute__((constructor))
.\"O and
.\"O .B __attribute__((destructor))
.\"O function attributes.
.\"O See the gcc info pages for information on these.
.\"O Constructor routines are executed before
.\"O .BR dlopen ()
.\"O returns, and destructor routines are executed before
.\"O .BR dlclose ()
.\"O returns.
Âå¤ï¤ê¤Ë¡¢¥é¥¤¥Ö¥é¥ê¤Ï
.B __attribute__((constructor))
¤ä
.B __attribute__((destructor))
¤Î´Ø¿ô°À­¤ò»È¤Ã¤ÆɬÍפʥ롼¥Á¥ó¤ò¥¨¥¯¥¹¥Ý¡¼¥È¤¹¤ë¤Î¤¬¤è¤¤¡£
¤³¤ì¤é¤Ë¤Ä¤¤¤Æ¤Ï gcc ¤Î info ¥Ú¡¼¥¸¤ò»²¾È¤Î¤³¤È¡£
constructor ¥ë¡¼¥Á¥ó¤Ï
.BR dlopen ()
¤¬Éüµ¢¤¹¤ëÁ°¤Ë¼Â¹Ô¤µ¤ì¡¢
destructor ¥ë¡¼¥Á¥ó¤Ï
.BR dlclose ()
¤¬Éüµ¢¤¹¤ëÁ°¤Ë¼Â¹Ô¤µ¤ì¤ë¡£
.\"O .SS Glibc extensions: dladdr() and dlvsym()
.SS GNU ¤Ç¤Î³ÈÄ¥: dladdr() ¤È dlvsym()
.\"O Glibc adds two functions not described by POSIX, with prototypes
glibc ¤Ç¤Ï POSIX ¤Ë¤Ïµ­ºÜ¤µ¤ì¤Æ¤¤¤Ê¤¤´Ø¿ô¤¬ 2¤ÄÄɲ䵤ì¤Æ¤¤¤ë¡£
¥×¥í¥È¥¿¥¤¥×¤Ï°Ê²¼¤ÎÄ̤ê¤Ç¤¢¤ë¡£
.sp
.nf
.\"O .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.BR "#define _GNU_SOURCE" "         /* feature_test_macros(7) »²¾È */"
.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
.\"O The function
.\"O .BR dladdr ()
.\"O takes a function pointer and tries to resolve name
.\"O and file where it is located.
.\"O Information is stored in the
.\"O .I Dl_info
.\"O structure:
´Ø¿ô
.BR dladdr ()
¤Ï¡¢´Ø¿ô¤Î¥Ý¥¤¥ó¥¿¤ò°ú¤­¿ô¤Ë¤È¤ê¡¢´Ø¿ô¤Î̾Á°¤È´Ø¿ô¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ë
¥Õ¥¡¥¤¥ë¤Î²ò·è¤ò»î¤ß¤ë¡£¾ðÊó¤Ï
.I Dl_info
¹½Â¤ÂΤ˳ÊǼ¤µ¤ì¤ë¡£
.sp
.in +4n
.nf
typedef struct {
    const char *dli_fname;  /* Pathname of shared object that
                               contains address */
    void       *dli_fbase;  /* Address at which shared object
                               is loaded */
    const char *dli_sname;  /* Name of nearest symbol with address
                               lower than \fIaddr\fP */
    void       *dli_saddr;  /* Exact address of symbol named
                               in \fIdli_sname\fP */
} Dl_info;
.fi
.in
.PP
.\"O If no symbol matching
.\"O .I addr
.\"O could be found, then
.\"O .I dli_sname
.\"O and
.\"O .I dli_saddr
.\"O are set to NULL.
.I addr
¤Ë¥Þ¥Ã¥Á¤¹¤ë¥·¥ó¥Ü¥ë¤¬¸«¤Ä¤«¤é¤Ê¤«¤Ã¤¿¾ì¹ç¡¢
.I dli_sname
¤È
.I dli_saddr
¤Ï NULL ¤Ë¥»¥Ã¥È¤µ¤ì¤ë¡£
.PP
.\"O .BR dladdr ()
.\"O returns 0 on error, and nonzero on success.
.BR dladdr ()
¤Ï¡¢¥¨¥é¡¼»þ¤Ë¤Ï 0 ¤òÊÖ¤·¡¢À®¸ù¤·¤¿¾ì¹ç¤Ï 0 °Ê³°¤òÊÖ¤¹¡£
.PP
.\"O The function
.\"O .BR dlvsym (),
.\"O provided by glibc since version 2.1,
.\"O does the same as
.\"O .BR dlsym ()
.\"O but takes a version string as an additional argument.
´Ø¿ô
.BR dlvsym ()
¤Ï
.BR dlsym ()
¤ÈƱ¤¸Æ°ºî¤ò¤¹¤ë¤¬¡¢¥Ð¡¼¥¸¥ç¥ó¤Îʸ»úÎó¤òÅϤ¹°ú¤­¿ô¤¬
Äɲ䵤ì¤Æ¤¤¤ëÅÀ¤¬°Û¤Ê¤ë
.RB ( dlvsym ()
¤Ï¥Ð¡¼¥¸¥ç¥ó 2.1 °Ê¹ß¤Î glibc ¤ÇÄ󶡤µ¤ì¤Æ¤¤¤ë)¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
.\"O POSIX.1-2003 describes
.\"O .BR dlclose (),
.\"O .BR dlerror (),
.\"O .BR dlopen (),
.\"O and
.\"O .BR dlsym ().
POSIX.1-2003 ¤Ë¤Ï
.BR dlclose (),
.BR dlerror (),
.BR dlopen (),
.BR dlsym ().
¤Îµ­ºÜ¤¬¤¢¤ë¡£
.\"O .SH NOTES
.SH Ãí°Õ
.\"O The symbols
.\"O .B RTLD_DEFAULT
.\"O and
.\"O .B RTLD_NEXT
.\"O are defined by
.\"O .I <dlfcn.h>
.\"O only when
.\"O .B _GNU_SOURCE
.\"O was defined before including it.
¥·¥ó¥Ü¥ë
.B RTLD_DEFAULT
¤È
.B RTLD_NEXT
¤Ï
.I <dlfcn.h>
¤ÇÄêµÁ¤µ¤ì¤Æ¤ª¤ê¡¢
.I <dlfcn.h>
¤Î¥¤¥ó¥¯¥ë¡¼¥ÉÁ°¤Ë
.B _GNU_SOURCE
¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ë¾ì¹ç¤Î¤ßÍ­¸ú¤È¤Ê¤ë¡£
.\" .LP
.\"O .\" The string returned by
.\"O .\" .BR dlerror ()
.\"O .\" should not be modified.
.\"O .\" Some systems give the prototype as
.\"O .\" .sp
.\"O .\" .in +5
.\"O .\" .B "const char *dlerror(void);"
.\"O .\" .in
.\" .BR dlerror ()
.\" ¤¬ÊÖ¤¹Ê¸»úÎó¤ÏÊѹ¹¤¹¤Ù¤­¤Ç¤Ï¤Ê¤¤¡£¥·¥¹¥Æ¥à¤Ë¤è¤Ã¤Æ¤Ï¡¢
.\" °Ê²¼¤Î¤è¤¦¤Ê¥×¥í¥È¥¿¥¤¥×¤Ë¤Ê¤Ã¤Æ¤¤¤ë¡£
.\" .sp
.\" .in +5
.\" .B "const char *dlerror(void);"
.\" .in

.\"O Since glibc 2.2.3,
.\"O .BR atexit (3)
.\"O can be used to register an exit handler that is automatically
.\"O called when a library is unloaded.
glibc 2.2.3 °Ê¹ß¤Ç¤Ï¡¢
.BR atexit (3)
¤ò»È¤Ã¤Æ¡¢¥é¥¤¥Ö¥é¥ê¤¬¥¢¥ó¥í¡¼¥É¤µ¤ì¤ëºÝ¤Ë¼«Æ°Åª¤Ë¸Æ¤Ó½Ð¤µ¤ì¤ë
½ªÎ»¥Ï¥ó¥É¥é (exit handler) ¤òÅÐÏ¿¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
.\"O .SS History
.SS Îò»Ë
.\"O The dlopen interface standard comes from SunOS.
.\"O That system also has
.\"O .BR dladdr (),
.\"O but not
.\"O .BR dlvsym ().
dlopen ¥¤¥ó¥¿¡¼¥Õ¥§¡¼¥¹¤Îɸ½à¤Ï SunOS ¤ò¤â¤È¤Ë¤·¤Æ¤¤¤ë¡£
SunOS ¤Ë¤Ï
.BR dladdr ()
¤â¤¢¤Ã¤¿¤¬¡¢
.BR dlvsym ()
¤Ï¤Ê¤«¤Ã¤¿¡£
.\"O .SH BUGS
.SH ¥Ð¥°
.\"O Sometimes, the function pointers you pass to
.\"O .BR dladdr ()
.\"O may surprise you.
.\"O On some architectures (notably i386 and x86_64),
.\"O .I dli_fname
.\"O and
.\"O .I dli_fbase
.\"O may end up pointing back at the object from which you called
.\"O .BR dladdr (),
.\"O even if the function used as an argument should come from
.\"O a dynamically linked library.
»þ¤È¤·¤Æ¡¢
.BR dladdr ()
¤ËÅϤ·¤¿´Ø¿ô¥Ý¥¤¥ó¥¿¤Ï¶Ã¤¯¤è¤¦¤ÊÃͤˤʤ뤳¤È¤¬¤¢¤ë¡£
¤¤¤¯¤Ä¤«¤Î¥¢¡¼¥­¥Æ¥¯¥Á¥ã (ÆÃ¤Ë i386 ¤È x86_64) ¤Ç¤Ï¡¢
°ú¤­¿ô¤È¤·¤Æ»ÈÍѤ·¤¿´Ø¿ô¤¬Æ°Åª¥ê¥ó¥¯¥é¥¤¥Ö¥é¥ê¤ÇÄêµÁ¤µ¤ì¤ë¤â¤Î¤Ç
¤¢¤Ã¤¿¤È¤·¤Æ¤â¡¢
.I dli_fname
¤È
.I dli_fbase
¤¬
.BR dladdr ()
¤ò¸Æ¤Ó½Ð¤·¤¿¥ª¥Ö¥¸¥§¥¯¥È¤ò»²¾È¤·¤¿¾õÂ֤ǽª¤ï¤Ã¤Æ¤¤¤ë¤³¤È¤¬¤¢¤ë¡£
.PP
.\"O The problem is that the function pointer will still be resolved
.\"O at compile time, but merely point to the
.\"O .I plt
.\"O (Procedure Linkage Table)
.\"O section of the original object (which dispatches the call after
.\"O asking the dynamic linker to resolve the symbol).
.\"O To work around this,
.\"O you can try to compile the code to be position-independent:
.\"O then, the compiler cannot prepare the pointer
.\"O at compile time anymore and today's
.\"O .BR gcc (1)
.\"O will generate code that just loads the final symbol address from the
.\"O .I got
.\"O (Global Offset Table) at run time before passing it to
.\"O .BR dladdr ().
.\"O motoki: ³ç¸ÌÆâ (which dispatches ¡Á) ¤ÎÉôʬ¤ÎÌõ¤Ë¼«¿®¤Ê¤·¡£
.\"O         which ¤Î¼ç¸ì¤Ï original object ¤Ç¤¤¤¤¤Î¤«?
ÌäÂê¤Ï¡¢´Ø¿ô¥Ý¥¤¥ó¥¿¤Î²ò·è¤Ïº£¤Ê¤ª¥³¥ó¥Ñ¥¤¥ë»þ¤Ë¹Ô¤ï¤ì¤ë¤¬¡¢
¤½¤Î¥Ý¥¤¥ó¥¿¤Ï¸µ¤Î¥ª¥Ö¥¸¥§¥¯¥È¤Î
.I plt
(Procedure Linkage Table) ¥»¥¯¥·¥ç¥ó¤ò»Ø¤·¤Æ¤¤¤ë¤À¤±¤À¤È¤¤¤¦ÅÀ¤Ë¤¢¤ë
(¥ª¥Ö¥¸¥§¥¯¥È¼«ÂΤϡ¢¥À¥¤¥Ê¥ß¥Ã¥¯¥ê¥ó¥«¤Ë¤è¤Ã¤Æ¥·¥ó¥Ü¥ë¤Î²ò·è¤¬¹Ô¤ï¤ì¤¿¸å¤Ë¡¢
´Ø¿ô¤Î¸Æ¤Ó½Ð¤·¤ò¹Ô¤¦)¡£
¤³¤ì¤ËÂн褹¤ëÊýË¡¤È¤·¤Æ¤Ï¡¢
¥³¡¼¥É¤ò position-independent ¤Ç¥³¥ó¥Ñ¥¤¥ë¤¹¤ë¤È¤¤¤¦ÊýË¡¤¬¤¢¤ë¡£
¤½¤¦¤¹¤ë¤È¡¢¥³¥ó¥Ñ¥¤¥é¤Ï¥³¥ó¥Ñ¥¤¥ë»þ¤Ë¥Ý¥¤¥ó¥¿¤òÍÑ°Õ¤¹¤ë¤³¤È¤¬¤Ç¤­¤º¡¢
º£Æü¤Î
.BR gcc (1)
¤Ç¤Ï¡¢¼Â¹Ô»þ¤Ë
.BR dladdr ()
¤Ë´Ø¿ô¥Ý¥¤¥ó¥¿¤òÅϤ¹Á°¤Ë¡¢
.I got
(Global Offset Table) ¤«¤éºÇ½ªÅª¤Ê¥·¥ó¥Ü¥ë¤Î¥¢¥É¥ì¥¹¤ò¥í¡¼¥É¤¹¤ë¤À¤±¤Î
¥³¡¼¥É¤¬À¸À®¤µ¤ì¤ë¡£
.\"O .SH EXAMPLE
.SH Îã
.\"O Load the math library, and print the cosine of 2.0:
math ¥é¥¤¥Ö¥é¥ê¤ò¥í¡¼¥É¤·¡¢2.0 ¤Î;¸¹¤òɽ¼¨¤¹¤ë
.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
.\"O If this program were in a file named "foo.c", you would build the program
.\"O with the following command:
¤³¤Î¥×¥í¥°¥é¥à¤ò "foo.c" ¤Ë½ñ¤¤¤¿¤È¤¹¤ë¤È¡¢°Ê²¼¤Î¥³¥Þ¥ó¥É¤Ç¥×¥í¥°¥é¥à¤ò
¥Ó¥ë¥É¤Ç¤­¤ë¡£
.in +4n
.LP
    gcc \-rdynamic \-o foo foo.c \-ldl
.in
.PP
.\"O Libraries exporting
.\"O .BR _init ()
.\"O and
.\"O .BR _fini ()
.\"O will want to be compiled as
.\"O follows, using \fIbar.c\fP as the example name:
.BR _init ()
¤È
.BR _fini ()
¤ò¥¨¥¯¥¹¥Ý¡¼¥È¤¹¤ë¥é¥¤¥Ö¥é¥ê¤Î¾ì¹ç¤Ï
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Îã¤È¤·¤Æ \fIbar.c\fP ¤ò¥³¥ó¥Ñ¥¤¥ë¤¹¤ë¾ì¹ç:
.in +4n
.LP
    gcc \-shared \-nostartfiles \-o bar bar.c
.in
.\"O .SH SEE ALSO
.SH ´ØÏ¢¹àÌÜ
.BR ld (1),
.BR ldd (1),
.BR dl_iterate_phdr (3),
.BR rtld-audit (7),
.BR ld.so (8),
.BR ldconfig (8),
ld.so info pages, gcc info pages, ld info pages