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1 .\" $NetBSD: elf_errmsg.3,v 1.2 2014/03/09 16:58:04 christos Exp $
2 .\"
3 .\" Copyright (c) 2006,2008 Joseph Koshy. 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
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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 Joseph Koshy ``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 Joseph Koshy be liable
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22 .\" liability, or tort (including negligence or otherwise) arising in any way
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26 .\" Id: elf_errmsg.3 189 2008-07-20 10:38:08Z jkoshy
27 .\"
28 .Dd June 11, 2006
29 .Os
30 .Dt ELF_ERRMSG 3
31 .Sh NAME
32 .Nm elf_errmsg ,
33 .Nm elf_errno
34 .Nd ELF library error message handling
35 .Sh LIBRARY
36 .Lb libelf
37 .Sh SYNOPSIS
38 .In libelf.h
39 .Ft int
40 .Fn elf_errno "void"
41 .Ft "const char *"
42 .Fn elf_errmsg "int error"
43 .Sh DESCRIPTION
44 When an error occurs during an ELF library API call, the library
45 encodes the error using an error number and stores the error number
46 internally for retrieval by the application at a later point of time.
47 Error numbers may contain an OS supplied error code in addition to
48 an ELF API specific error code.
49 An error number value of zero indicates no error.
50 .Pp
51 Function
52 .Fn elf_errno
53 is used to retrieve the last error recorded by the ELF library.
54 Invoking this function has the side-effect of resetting the
55 ELF library's recorded error number to zero.
56 .Pp
57 The function
58 .Fn elf_errmsg
59 returns a null-terminated string with a human readable
60 description of the error specified in argument
61 .Ar error .
62 A zero value for argument
63 .Ar error
64 retrieves the most recent error encountered by the ELF
65 library.
66 An argument value of -1 behaves identically, except that
67 it guarantees a non-NULL return from
68 .Fn elf_errmsg .
69 .Sh RETURN VALUES
70 Function
71 .Fn elf_errno
72 returns a non-zero value encoding the last error encountered
73 by the ELF library, or zero if no error was encountered.
74 .Pp
75 Function
76 .Fn elf_errmsg
77 returns a pointer to library local storage for non-zero values
78 of argument
79 .Ar error .
80 With a zero argument, the function will return a NULL pointer if no
81 error had been encountered by the library, or will return a pointer to
82 library local storage containing an appropriate message otherwise.
83 .Sh EXAMPLES
84 Clearing the ELF library's recorded error number can be accomplished
85 by invoking
86 .Fn elf_errno
87 and discarding its return value.
88 .Bd -literal -offset indent
89 /* clear error */
90 (void) elf_errno();
91 .Ed
92 .Pp
93 Retrieving a human-readable description of the current error number
94 can be done with the following snippet:
95 .Bd -literal -offset indent
96 int err;
97 const char *errmsg;
98 \&...
99 err = elf_errno();
100 if (err != 0)
101 errmsg = elf_errmsg(err);
102 .Ed
103 .Sh SEE ALSO
104 .Xr elf 3 ,
105 .Xr gelf 3
106 .Sh BUGS
107 Function
108 .Fn elf_errmsg
109 is not localized.