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.\"
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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
44When an error occurs during an ELF library API call, the library
45encodes the error using an error number and stores the error number
46internally for retrieval by the application at a later point of time.
47Error numbers may contain an OS supplied error code in addition to
48an ELF API specific error code.
49An error number value of zero indicates no error.
50.Pp
51Function
52.Fn elf_errno
53is used to retrieve the last error recorded by the ELF library.
54Invoking this function has the side-effect of resetting the
55ELF library's recorded error number to zero.
56.Pp
57The function
58.Fn elf_errmsg
59returns a null-terminated string with a human readable
60description of the error specified in argument
61.Ar error .
62A zero value for argument
63.Ar error
64retrieves the most recent error encountered by the ELF
65library.
66An argument value of -1 behaves identically, except that
67it guarantees a non-NULL return from
68.Fn elf_errmsg .
69.Sh RETURN VALUES
70Function
71.Fn elf_errno
72returns a non-zero value encoding the last error encountered
73by the ELF library, or zero if no error was encountered.
74.Pp
75Function
76.Fn elf_errmsg
77returns a pointer to library local storage for non-zero values
78of argument
79.Ar error .
80With a zero argument, the function will return a NULL pointer if no
81error had been encountered by the library, or will return a pointer to
82library local storage containing an appropriate message otherwise.
83.Sh EXAMPLES
84Clearing the ELF library's recorded error number can be accomplished
85by invoking
86.Fn elf_errno
87and discarding its return value.
88.Bd -literal -offset indent
89/* clear error */
90(void) elf_errno();
91.Ed
92.Pp
93Retrieving a human-readable description of the current error number
94can be done with the following snippet:
95.Bd -literal -offset indent
96int err;
97const char *errmsg;
98\&...
99err = elf_errno();
100if (err != 0)
101	errmsg = elf_errmsg(err);
102.Ed
103.Sh SEE ALSO
104.Xr elf 3 ,
105.Xr gelf 3
106.Sh BUGS
107Function
108.Fn elf_errmsg
109is not localized.
110