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