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.\" $DragonFly: src/lib/libc/gen/dladdr.3,v 1.2 2003/06/17 04:26:42 dillon Exp $ 28.\" 29.Dd February 5, 1998 30.Os 31.Dt DLADDR 3 32.Sh NAME 33.Nm dladdr 34.Nd find the shared object containing a given address 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In dlfcn.h 39.Ft int 40.Fn dladdr "const void *addr" "Dl_info *info" 41.Sh DESCRIPTION 42The 43.Fn dladdr 44function 45queries the dynamic linker for information about the shared object 46containing the address 47.Fa addr . 48The information is returned in the structure specified by 49.Fa info . 50The structure contains at least the following members: 51.Bl -tag -width "XXXconst char *dli_fname" 52.It Li "const char *dli_fname" 53The pathname of the shared object containing the address. 54.It Li "void *dli_fbase" 55The base address at which the shared object is mapped into the 56address space of the calling process. 57.It Li "const char *dli_sname" 58The name of the nearest run-time symbol with a value less than or 59equal to 60.Fa addr . 61When possible, the symbol name is returned as it would appear in C 62source code. 63.Pp 64If no symbol with a suitable value is found, both this field and 65.Va dli_saddr 66are set to 67.Dv NULL . 68.It Li "void *dli_saddr" 69The value of the symbol returned in 70.Li dli_sname . 71.El 72.Pp 73The 74.Fn dladdr 75function 76is available only in dynamically linked programs. 77.Sh ERRORS 78If a mapped shared object containing 79.Fa addr 80cannot be found, 81.Fn dladdr 82returns 0. 83In that case, a message detailing the failure can be retrieved by 84calling 85.Fn dlerror . 86.Pp 87On success, a non-zero value is returned. 88.Sh SEE ALSO 89.Xr rtld 1 , 90.Xr dlopen 3 91.Sh HISTORY 92The 93.Fn dladdr 94function first appeared in the Solaris operating system. 95.Sh BUGS 96This implementation is bug-compatible with the Solaris 97implementation. In particular, the following bugs are present: 98.Bl -bullet 99.It 100If 101.Fa addr 102lies in the main executable rather than in a shared library, the 103pathname returned in 104.Va dli_fname 105may not be correct. The pathname is taken directly from 106.Va argv[0] 107of the calling process. When executing a program specified by its 108full pathname, most shells set 109.Va argv[0] 110to the pathname. But this is not required of shells or guaranteed 111by the operating system. 112.It 113If 114.Fa addr 115is of the form 116.Va &func , 117where 118.Va func 119is a global function, its value may be an unpleasant surprise. In 120dynamically linked programs, the address of a global function is 121considered to point to its program linkage table entry, rather than to 122the entry point of the function itself. This causes most global 123functions to appear to be defined within the main executable, rather 124than in the shared libraries where the actual code resides. 125.It 126Returning 0 as an indication of failure goes against long-standing 127Unix tradition. 128.El 129