1explain_eventfd(3) Library Functions Manual explain_eventfd(3)
2
6 explain_eventfd - explain eventfd(2) errors
7
9 #include <libexplain/eventfd.h>
10 const char *explain_eventfd(unsigned int initval, int flags);
11 const char *explain_errno_eventfd(int errnum, unsigned int initval, int
12 flags);
13 void explain_message_eventfd(char *message, int message_size, unsigned
14 int initval, int flags);
15 void explain_message_errno_eventfd(char *message, int message_size, int
16 errnum, unsigned int initval, int flags);
17
19 These functions may be used to obtain explanations for errors returned
20 by the eventfd(2) system call.
21 explain_eventfd
23 const char *explain_eventfd(unsigned int initval, int flags);
24 The explain_eventfd function is used to obtain an explanation of an
26 error returned by the eventfd(2) system call. The least the message
27 will contain is the value of strerror(errno), but usually it will do
28 much better, and indicate the underlying cause in more detail.
29 The errno global variable will be used to obtain the error value to be
31 decoded.
32 initval The original initval, exactly as passed to the eventfd(2) sys‐
34 tem call.
35 flags The original flags, exactly as passed to the eventfd(2) system
37 call.
38 Returns:
40 The message explaining the error. This message buffer is shared
41 by all libexplain functions which do not supply a buffer in
42 their argument list. This will be overwritten by the next call
43 to any libexplain function which shares this buffer, including
44 other threads.
45 Note: This function is not thread safe, because it shares a return buf‐
47 fer across all threads, and many other functions in this library.
48 Example: This function is intended to be used in a fashion similar to
50 the following example:
51 int result = eventfd(initval, flags);
52 if (result < 0)
53 {
54 fprintf(stderr, "%s\n", explain_eventfd(initval, flags));
55 exit(EXIT_FAILURE);
56 }
57 The above code example is available pre‐packaged as the
59 explain_eventfd_or_die(3) function.
60 explain_errno_eventfd
62 const char *explain_errno_eventfd(int errnum, unsigned int initval, int
63 flags);
64 The explain_errno_eventfd function is used to obtain an explanation of
66 an error returned by the eventfd(2) system call. The least the message
67 will contain is the value of strerror(errno), but usually it will do
68 much better, and indicate the underlying cause in more detail.
69 errnum The error value to be decoded, usually obtained from the errno
71 global variable just before this function is called. This is
72 necessary if you need to call any code between the system call
73 to be explained and this function, because many libc functions
74 will alter the value of errno.
75 initval The original initval, exactly as passed to the eventfd(2) sys‐
77 tem call.
78 flags The original flags, exactly as passed to the eventfd(2) system
80 call.
81 Returns:
83 The message explaining the error. This message buffer is shared
84 by all libexplain functions which do not supply a buffer in
85 their argument list. This will be overwritten by the next call
86 to any libexplain function which shares this buffer, including
87 other threads.
88 Note: This function is not thread safe, because it shares a return buf‐
90 fer across all threads, and many other functions in this library.
91 Example: This function is intended to be used in a fashion similar to
93 the following example:
94 int result = eventfd(initval, flags);
95 if (result < 0)
96 {
97 int err = errno;
98 fprintf(stderr, "%s\n", explain_errno_eventfd(err, initval,
99 flags));
100 exit(EXIT_FAILURE);
101 }
102 The above code example is available pre‐packaged as the
104 explain_eventfd_or_die(3) function.
105 explain_message_eventfd
107 void explain_message_eventfd(char *message, int message_size, unsigned
108 int initval, int flags);
109 The explain_message_eventfd function is used to obtain an explanation
111 of an error returned by the eventfd(2) system call. The least the mes‐
112 sage will contain is the value of strerror(errno), but usually it will
113 do much better, and indicate the underlying cause in more detail.
114 The errno global variable will be used to obtain the error value to be
116 decoded.
117 message The location in which to store the returned message. If a suit‐
119 able message return buffer is supplied, this function is thread
120 safe.
121 message_size
123 The size in bytes of the location in which to store the
124 returned message.
125 initval The original initval, exactly as passed to the eventfd(2) sys‐
127 tem call.
128 flags The original flags, exactly as passed to the eventfd(2) system
130 call.
131 Example: This function is intended to be used in a fashion similar to
133 the following example:
134 int result = eventfd(initval, flags);
135 if (result < 0)
136 {
137 char message[3000];
138 explain_message_eventfd(message, sizeof(message), initval,
139 flags);
140 fprintf(stderr, "%s\n", message);
141 exit(EXIT_FAILURE);
142 }
143 The above code example is available pre‐packaged as the
145 explain_eventfd_or_die(3) function.
146 explain_message_errno_eventfd
148 void explain_message_errno_eventfd(char *message, int message_size, int
149 errnum, unsigned int initval, int flags);
150 The explain_message_errno_eventfd function is used to obtain an expla‐
152 nation of an error returned by the eventfd(2) system call. The least
153 the message will contain is the value of strerror(errno), but usually
154 it will do much better, and indicate the underlying cause in more
155 detail.
156 message The location in which to store the returned message. If a suit‐
158 able message return buffer is supplied, this function is thread
159 safe.
160 message_size
162 The size in bytes of the location in which to store the
163 returned message.
164 errnum The error value to be decoded, usually obtained from the errno
166 global variable just before this function is called. This is
167 necessary if you need to call any code between the system call
168 to be explained and this function, because many libc functions
169 will alter the value of errno.
170 initval The original initval, exactly as passed to the eventfd(2) sys‐
172 tem call.
173 flags The original flags, exactly as passed to the eventfd(2) system
175 call.
176 Example: This function is intended to be used in a fashion similar to
178 the following example:
179 int result = eventfd(initval, flags);
180 if (result < 0)
181 {
182 int err = errno;
183 char message[3000];
184 explain_message_errno_eventfd(message, sizeof(message), err,
185 initval, flags);
186 fprintf(stderr, "%s\n", message);
187 exit(EXIT_FAILURE);
188 }
189 The above code example is available pre‐packaged as the
191 explain_eventfd_or_die(3) function.
192
194 eventfd(2)
195 create a file descriptor for event notification
196 explain_eventfd_or_die(3)
198 create a file descriptor for event notification and report
199 errors
200
202 libexplain version 1.4
203 Copyright (C) 2009 Peter Miller
204 explain_eventfd(3)