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.Dd February 5, 1998 27.Dt DLADDR 3 28.Os 29.Sh NAME 30.Nm dladdr 31.Nd find the shared object containing a given address 32.Sh LIBRARY 33.Lb libc 34.Sh SYNOPSIS 35.In dlfcn.h 36.Ft int 37.Fn dladdr "const void *addr" "Dl_info *info" 38.Sh DESCRIPTION 39The 40.Fn dladdr 41function 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 70The 71.Fn dladdr 72function 73is available only in dynamically linked programs. 74.Sh ERRORS 75If a mapped shared object containing 76.Fa addr 77cannot be found, 78.Fn dladdr 79returns 0. 80In that case, a message detailing the failure can be retrieved by 81calling 82.Fn dlerror . 83.Pp 84On success, a non-zero value is returned. 85.Sh SEE ALSO 86.Xr rtld 1 , 87.Xr dlopen 3 88.Sh HISTORY 89The 90.Fn dladdr 91function first appeared in the Solaris operating system. 92.Sh BUGS 93This implementation is bug-compatible with the Solaris 94implementation. 95In particular, the following bugs are present: 96.Bl -bullet 97.It 98If 99.Fa addr 100lies in the main executable rather than in a shared library, the 101pathname returned in 102.Va dli_fname 103may not be correct. 104The pathname is taken directly from 105.Va argv[0] 106of the calling process. 107When executing a program specified by its 108full pathname, most shells set 109.Va argv[0] 110to the pathname. 111But this is not required of shells or guaranteed 112by the operating system. 113.It 114If 115.Fa addr 116is of the form 117.Va &func , 118where 119.Va func 120is a global function, its value may be an unpleasant surprise. 121In 122dynamically linked programs, the address of a global function is 123considered to point to its program linkage table entry, rather than to 124the entry point of the function itself. 125This causes most global 126functions to appear to be defined within the main executable, rather 127than in the shared libraries where the actual code resides. 128.It 129Returning 0 as an indication of failure goes against long-standing 130Unix tradition. 131.El 132