198 lines
5.8 KiB
Groff
198 lines
5.8 KiB
Groff
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.\" This source code is a product of Sun Microsystems, Inc. and is provided
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.\" for unrestricted use provided that this legend is included on all tape
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.\" media and as a part of the software program in whole or part. Users
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.\" may copy or modify this source code without charge, but are not authorized
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.\" to license or distribute it to anyone else except as part of a product or
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.\" program developed by the user.
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.\"
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.\" THIS PROGRAM CONTAINS SOURCE CODE COPYRIGHTED BY SUN MICROSYSTEMS, INC.
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.\" SUN MICROSYSTEMS, INC., MAKES NO REPRESENTATIONS ABOUT THE SUITABLITY
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.\" OF SUCH SOURCE CODE FOR ANY PURPOSE. IT IS PROVIDED "AS IS" WITHOUT
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.\" EXPRESS OR IMPLIED WARRANTY OF ANY KIND. SUN MICROSYSTEMS, INC. DISCLAIMS
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.\" ALL WARRANTIES WITH REGARD TO SUCH SOURCE CODE, INCLUDING ALL IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN
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.\" NO EVENT SHALL SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY SPECIAL, INDIRECT,
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.\" INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
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.\" FROM USE OF SUCH SOURCE CODE, REGARDLESS OF THE THEORY OF LIABILITY.
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.\"
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.\" This source code is provided with no support and without any obligation on
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.\" the part of Sun Microsystems, Inc. to assist in its use, correction,
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.\" modification or enhancement.
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.\"
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.\" SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
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.\" INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS
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.\" SOURCE CODE OR ANY PART THEREOF.
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.\"
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.\" Sun Microsystems, Inc.
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.\" 2550 Garcia Avenue
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.\" Mountain View, California 94043
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.\"
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.\" Copyright (c) 1991 Sun Microsystems, Inc.
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.\"
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.\" @(#) dlopen.3 1.6 90/01/31 SMI
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.TH DLOPEN 3 "24 September 1989"
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.SH NAME
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dlopen, dlsym, dlerror, dlclose \- simple programmatic interface to the dynamic linker
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.SH SYNOPSIS
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.nf
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.ft B
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#include <dlfcn.h>
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.LP
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.ft B
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.nf
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void *dlopen(path, mode)
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const char *path; int mode;
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.fi
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.ft R
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.LP
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.ft B
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.nfvoid *dlopen(path, mode)
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.fi
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.ft R
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.LP
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.ft B
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.nf
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void *dlsym(handle, symbol)
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void *handle; const char *symbol;
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.fi
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.ft R
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.LP
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.ft B
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.nf
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char *dlerror(\|)
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.fi
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.ft R
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.LP
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.ft B
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.nf
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int dlclose(handle);
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void *handle;
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.fi
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.ft R
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.ft R
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.fi
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.SH DESCRIPTION
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.IX "dlopen()" "" "\fLdlopen()\fP \(em dynamically load a shared object"
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.IX "programmatic interface to dynamic linker" dlopen() "" \fLdlopen()\fP
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.IX "dlsym()" "" "\fLdlsym()\fP \(em dynamically lookup a symbol"
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.IX "programmatic interface to dynamic linker" dlsym "" \fLdlsym()\fP
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.IX "dlerror()" "" "\fLdlerror()\fP \(em dynamic linking error string"
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.IX "programmatic interface to dynamic linker" dlerror() "" \fLdlerror()\fP
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.IX "dlclose()" "" "\fLdlclose()\fP \(em unload a shared object"
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.IX "programmatic interface to dynamic linker" dlclose() "" \fLdlclose()\fP
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.LP
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These functions provide a simple programmatic interface to the services of the
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dynamic link-editor.
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Operations are provided to add a new shared object to an
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program's address space, obtain the address bindings of symbols defined by such
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objects, and to remove such objects when their use is no longer required.
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.LP
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.B dlopen(\|)
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provides access to the shared object in
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.IR path ,
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returning a descriptor that can be used for later
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references to the object in calls to
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.B dlsym(\|)
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and
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.BR dlclose(\|) .
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If
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.I path
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was not in the address space prior to the call to
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.BR dlopen(\|) ,
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then it will be placed in the address space, and if it defines a function
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with the name
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.I _init
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that function will be called by
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.BR dlopen(\|) .
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If, however,
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.I path
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has already been placed in the address space in a previous call to
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.BR dlopen(\|) ,
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then it will not be added a
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second time, although a count of
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.B dlopen(\|)
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operations on
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.I path
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will be maintained.
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.I mode
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is an integer containing flags describing options to be applied to the opening
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and loading process \(em it is reserved for future expansion and must always have
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the value 1.
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A null pointer supplied for
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.I path
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is interpreted as a reference to the \*(lqmain\*(rq
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executable of the process.
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If
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.B dlopen(\|)
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fails, it will return a null pointer.
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.LP
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.B dlsym(\|)
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returns the address binding of the symbol described in the null-terminated
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character string
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.I symbol
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as it occurs in the shared object identified by
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.IR handle .
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The symbols exported by objects added to the address space by
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.B dlopen(\|)
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can be accessed
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.I only
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through calls to
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.BR dlsym(\|) ,
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such symbols do not supersede any definition of those symbols already present
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in the address space when the object is loaded, nor are they available to
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satisfy \*(lqnormal\*(rq dynamic linking references.
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.B dlsym(\|)
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returns a null pointer if the symbol can not be found.
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A null pointer supplied as the value of
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.I handle
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is interpreted as a reference to the executable from which the call to
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.B dlsym(\|)
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is being made \(em thus a shared object can reference its own symbols.
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.LP
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.B dlerror
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returns a null-terminated character string describing the last error that
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occurred during a
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.BR dlopen(\|) ,
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.BR dlsym(\|) ,
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or
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.BR dlclose(\|) .
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If no such error has occurred, then
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.B dlerror(\|)
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will return a null pointer.
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At each call to
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.BR dlerror(\|) ,
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the \*(lqlast error\*(rq indication will be reset, thus in the case of two calls
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to
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.BR dlerror(\|) ,
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and where the second call follows the first immediately, the second call
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will always return a null pointer.
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.LP
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.B dlclose(\|)
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deletes a reference to the shared object referenced by
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.IR handle .
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If the reference count drops to 0, then if the object referenced by
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.I handle
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defines a function
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.IR _fini ,
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that function will be called, the object
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removed from the address space, and
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.I handle
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destroyed.
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If
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.B dlclose(\|)
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is successful, it will return a value of 0.
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A failing call to
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.B dlclose(\|)
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will return a non-zero value.
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.LP
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The object-intrinsic functions
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.I _init
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and
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.I _fini
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are called with no arguments and treated as though their types were
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.BR void .
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.SH SEE ALSO
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.BR ld (1),
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.BR link (5)
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.SH NOTES
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