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.\" $FreeBSD$ 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 41The 42.Fn dladdr 43function 44queries the dynamic linker for information about the shared object 45containing the address 46.Fa addr . 47The information is returned in the structure specified by 48.Fa info . 49The structure contains at least the following members: 50.Bl -tag -width "XXXconst char *dli_fname" 51.It Li "const char *dli_fname" 52The pathname of the shared object containing the address. 53.It Li "void *dli_fbase" 54The base address at which the shared object is mapped into the 55address space of the calling process. 56.It Li "const char *dli_sname" 57The name of the nearest run-time symbol with a value less than or 58equal to 59.Fa addr . 60When possible, the symbol name is returned as it would appear in C 61source code. 62.Pp 63If no symbol with a suitable value is found, both this field and 64.Va dli_saddr 65are set to 66.Dv NULL . 67.It Li "void *dli_saddr" 68The value of the symbol returned in 69.Li dli_sname . 70.El 71.Pp 72The 73.Fn dladdr 74function 75is available only in dynamically linked programs. 76.Sh ERRORS 77If a mapped shared object containing 78.Fa addr 79cannot be found, 80.Fn dladdr 81returns 0. 82In that case, a message detailing the failure can be retrieved by 83calling 84.Fn dlerror . 85.Pp 86On success, a non-zero value is returned. 87.Sh SEE ALSO 88.Xr rtld 1 , 89.Xr dlopen 3 90.Sh HISTORY 91The 92.Fn dladdr 93function first appeared in the Solaris operating system. 94.Sh BUGS 95This implementation is bug-compatible with the Solaris 96implementation. In particular, the following bugs are present: 97.Bl -bullet 98.It 99If 100.Fa addr 101lies in the main executable rather than in a shared library, the 102pathname returned in 103.Va dli_fname 104may not be correct. The pathname is taken directly from 105.Va argv[0] 106of the calling process. When executing a program specified by its 107full pathname, most shells set 108.Va argv[0] 109to the pathname. But this is not required of shells or guaranteed 110by the operating system. 111.It 112If 113.Fa addr 114is of the form 115.Va &func , 116where 117.Va func 118is a global function, its value may be an unpleasant surprise. In 119dynamically linked programs, the address of a global function is 120considered to point to its program linkage table entry, rather than to 121the entry point of the function itself. This causes most global 122functions to appear to be defined within the main executable, rather 123than in the shared libraries where the actual code resides. 124.It 125Returning 0 as an indication of failure goes against long-standing 126Unix tradition. 127.El 128