129 lines
4.1 KiB
Groff
129 lines
4.1 KiB
Groff
.\" $NetBSD: dlfcn.3,v 1.4 1997/03/14 01:02:45 cgd Exp $
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.\"
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.\" Copyright (c) 1995 Paul Kranenburg
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Paul Kranenburg.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd September 30, 1995
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.Dt DLFCN 3
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.Os
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.Sh NAME
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.Nm dlopen ,
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.Nm dlclose ,
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.Nm dlsym ,
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.Nm dlctl ,
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.Nm dlerror
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.Nd dynamic link interface
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.Sh SYNOPSIS
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.Fd #include <dlfcn.h>
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.Ft "void *"
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.Fn dlopen "char *path" "int mode"
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.Ft "int"
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.Fn dlclose "void *handle"
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.Ft "void *"
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.Fn dlsym "void *handle" "char *symbol"
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.Ft "int"
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.Fn dlctl "void *handle" "int cmd" "void *data"
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.Ft "char *"
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.Fn dlerror "void"
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.Sh DESCRIPTION
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These functions provide an interface to the run-time linker
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.Xr ld.so .
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They allow new shared objects to be loaded into the process' address space
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under program control.
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The
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.Fn dlopen
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function takes a name of a shared object as the first argument. The
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shared object is mapped into the address space, relocated and its external
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references are resolved in the same way as is done with the implicitly loaded
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shared libraries at program startup. The argument can either be an absolute
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pathname or it can be of the form
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.Sm off
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.Do Xo lib Ao name Ac .so
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.Op .xx Op .yy Xc
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.Dc
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.Sm on
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in which case the same library search rules apply that are used for
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.Dq intrinsic
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shared library searches.
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The second argument has currently no effect, but should be set to
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.Dv DL_LAZY
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for future compatibility.
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.Fn dlopen
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returns a handle to be used in calls to
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.Fn dlclose ,
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.Fn dlsym
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and
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.Fn dlctl .
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If the named shared object has already
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been loaded by a previous call to
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.Fn dlopen
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.Pq and not yet unloaded by Fn dlclose ,
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a handle refering to the resident copy is returned.
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.Pp
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.Fn dlclose
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unlinks and removes the object referred to by
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.Fa handle
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from the process address space. If multiple calls to
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.fn dlopen
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have been done on this object
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.Po or the object was one loaded at startup time
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.Pc
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the object is removed when its reference count drops to zero.
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.Pp
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.Fn dlsym
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looks for a definition of
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.Fa symbol
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in the shared object designated by
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.Fa handle .
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The symbols address is returned. If the symbol cannot be resolved,
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.Dv NULL
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is returned.
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.Pp
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.Fn dlctl
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provides an interface similar to
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.Xr ioctl 2
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to control several aspects of the run-time linker's operation. This interface
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is
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.Ud .
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.Pp
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.Fn dlerror
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return a character string representing the most recent error that has
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occurred while processing one of the other functions described here.
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.Sh SEE ALSO
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.Xr ld 1 ,
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.Xr rtld 1 ,
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.Xr link 5
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.Sh HISTORY
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Some of the
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.Nm dl*
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functions first appeared in SunOS 4.
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.Sh BUGS
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An error that occurs while processing a
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.Fn dlopen
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request results in the termination of the program.
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