[dragonfly.git] / lib / libc / gen / dladdr.3

.\"
.\" Copyright (c) 1998 John D. Polstra
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/libc/gen/dladdr.3,v 1.3.2.4 2003/03/15 15:11:05 trhodes Exp $
.\"
.Dd February 5, 1998
.Os
.Dt DLADDR 3
.Sh NAME
.Nm dladdr
.Nd find the shared object containing a given address
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In dlfcn.h
.Ft int
.Fn dladdr "const void *addr" "Dl_info *info"
.Sh DESCRIPTION
The
.Fn dladdr
function queries the dynamic linker for information about the shared object
containing the address
.Fa addr .
The information is returned in the structure specified by
.Fa info .
The structure contains at least the following members:
.Bl -tag -width "XXXconst char *dli_fname"
.It Li "const char *dli_fname"
The pathname of the shared object containing the address.
.It Li "void *dli_fbase"
The base address at which the shared object is mapped into the
address space of the calling process.
.It Li "const char *dli_sname"
The name of the nearest run-time symbol with a value less than or
equal to
.Fa addr .
When possible, the symbol name is returned as it would appear in C
source code.
.Pp
If no symbol with a suitable value is found, both this field and
.Va dli_saddr
are set to
.Dv NULL .
.It Li "void *dli_saddr"
The value of the symbol returned in
.Li dli_sname .
.El
.Pp
The
.Fn dladdr
function is available only in dynamically linked programs.
.Sh ERRORS
If a mapped shared object containing
.Fa addr
cannot be found,
.Fn dladdr
returns 0.
In that case, a message detailing the failure can be retrieved by
calling
.Fn dlerror .
.Pp
On success, a non-zero value is returned.
.Sh SEE ALSO
.Xr rtld 1 ,
.Xr dlopen 3
.Sh HISTORY
The
.Fn dladdr
function first appeared in the Solaris operating system.
.Sh BUGS
This implementation is bug-compatible with the Solaris
implementation.  In particular, the following bugs are present:
.Bl -bullet
.It
If
.Fa addr
lies in the main executable rather than in a shared library, the
pathname returned in
.Va dli_fname
may not be correct.  The pathname is taken directly from
.Va argv[0]
of the calling process.  When executing a program specified by its
full pathname, most shells set
.Va argv[0]
to the pathname.  But this is not required of shells or guaranteed
by the operating system.
.It
If
.Fa addr
is of the form
.Va &func ,
where
.Va func
is a global function, its value may be an unpleasant surprise.  In
dynamically linked programs, the address of a global function is
considered to point to its program linkage table entry, rather than to
the entry point of the function itself.  This causes most global
functions to appear to be defined within the main executable, rather
than in the shared libraries where the actual code resides.
.It
Returning 0 as an indication of failure goes against long-standing
Unix tradition.
.El
Commit	Line	Data
984263bc MD	1	.\"
	2	.\" Copyright (c) 1998 John D. Polstra
	3	.\" All rights reserved.
	4	.\"
	5	.\" Redistribution and use in source and binary forms, with or without
	6	.\" modification, are permitted provided that the following conditions
	7	.\" are met:
	8	.\" 1. Redistributions of source code must retain the above copyright
	9	.\" notice, this list of conditions and the following disclaimer.
	10	.\" 2. Redistributions in binary form must reproduce the above copyright
	11	.\" notice, this list of conditions and the following disclaimer in the
	12	.\" documentation and/or other materials provided with the distribution.
	13	.\"
	14	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	15	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	16	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	17	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	18	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	19	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	20	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	21	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	22	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	23	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	24	.\" SUCH DAMAGE.
	25	.\"
	26	.\" $FreeBSD: src/lib/libc/gen/dladdr.3,v 1.3.2.4 2003/03/15 15:11:05 trhodes Exp $
	27	.\"
	28	.Dd February 5, 1998
	29	.Os
	30	.Dt DLADDR 3
	31	.Sh NAME
	32	.Nm dladdr
	33	.Nd find the shared object containing a given address
	34	.Sh LIBRARY
	35	.Lb libc
	36	.Sh SYNOPSIS
	37	.In dlfcn.h
	38	.Ft int
	39	.Fn dladdr "const void addr" "Dl_info info"
	40	.Sh DESCRIPTION
	41	The
	42	.Fn dladdr
139b8f34	43	function queries the dynamic linker for information about the shared object
984263bc MD	44	containing the address
	45	.Fa addr .
	46	The information is returned in the structure specified by
	47	.Fa info .
	48	The structure contains at least the following members:
	49	.Bl -tag -width "XXXconst char *dli_fname"
	50	.It Li "const char *dli_fname"
	51	The pathname of the shared object containing the address.
	52	.It Li "void *dli_fbase"
	53	The base address at which the shared object is mapped into the
	54	address space of the calling process.
	55	.It Li "const char *dli_sname"
	56	The name of the nearest run-time symbol with a value less than or
	57	equal to
	58	.Fa addr .
	59	When possible, the symbol name is returned as it would appear in C
	60	source code.
	61	.Pp
	62	If no symbol with a suitable value is found, both this field and
	63	.Va dli_saddr
	64	are set to
	65	.Dv NULL .
	66	.It Li "void *dli_saddr"
	67	The value of the symbol returned in
	68	.Li dli_sname .
	69	.El
	70	.Pp
	71	The
	72	.Fn dladdr
139b8f34	73	function is available only in dynamically linked programs.
984263bc MD	74	.Sh ERRORS
	75	If a mapped shared object containing
	76	.Fa addr
	77	cannot be found,
	78	.Fn dladdr
	79	returns 0.
	80	In that case, a message detailing the failure can be retrieved by
	81	calling
	82	.Fn dlerror .
	83	.Pp
	84	On success, a non-zero value is returned.
	85	.Sh SEE ALSO
	86	.Xr rtld 1 ,
	87	.Xr dlopen 3
	88	.Sh HISTORY
	89	The
	90	.Fn dladdr
	91	function first appeared in the Solaris operating system.
	92	.Sh BUGS
	93	This implementation is bug-compatible with the Solaris
	94	implementation. In particular, the following bugs are present:
	95	.Bl -bullet
	96	.It
	97	If
	98	.Fa addr
	99	lies in the main executable rather than in a shared library, the
	100	pathname returned in
	101	.Va dli_fname
	102	may not be correct. The pathname is taken directly from
	103	.Va argv[0]
	104	of the calling process. When executing a program specified by its
	105	full pathname, most shells set
	106	.Va argv[0]
	107	to the pathname. But this is not required of shells or guaranteed
	108	by the operating system.
	109	.It
	110	If
	111	.Fa addr
	112	is of the form
	113	.Va &func ,
	114	where
	115	.Va func
	116	is a global function, its value may be an unpleasant surprise. In
	117	dynamically linked programs, the address of a global function is
	118	considered to point to its program linkage table entry, rather than to
	119	the entry point of the function itself. This causes most global
	120	functions to appear to be defined within the main executable, rather
	121	than in the shared libraries where the actual code resides.
	122	.It
	123	Returning 0 as an indication of failure goes against long-standing
	124	Unix tradition.
	125	.El