Provided by: libexplain-dev_1.4.D001-2_amd64 
NAME
explain_eventfd - explain eventfd(2) errors
SYNOPSIS
#include <libexplain/eventfd.h>
const char *explain_eventfd(unsigned int initval, int flags);
const char *explain_errno_eventfd(int errnum, unsigned int initval, int flags);
void explain_message_eventfd(char *message, int message_size, unsigned int initval, int
flags);
void explain_message_errno_eventfd(char *message, int message_size, int errnum, unsigned
int initval, int flags);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the eventfd(2)
system call.
explain_eventfd
const char *explain_eventfd(unsigned int initval, int flags);
The explain_eventfd function is used to obtain an explanation of an error returned by the
eventfd(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
The errno global variable will be used to obtain the error value to be decoded.
initval The original initval, exactly as passed to the eventfd(2) system call.
flags The original flags, exactly as passed to the eventfd(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain
functions which do not supply a buffer in their argument list. This will be
overwritten by the next call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return buffer across all
threads, and many other functions in this library.
Example: This function is intended to be used in a fashion similar to the following
example:
int result = eventfd(initval, flags);
if (result < 0)
{
fprintf(stderr, "%s\n", explain_eventfd(initval, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_eventfd_or_die(3)
function.
explain_errno_eventfd
const char *explain_errno_eventfd(int errnum, unsigned int initval, int flags);
The explain_errno_eventfd function is used to obtain an explanation of an error returned
by the eventfd(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
errnum The error value to be decoded, usually obtained from the errno global variable
just before this function is called. This is necessary if you need to call any
code between the system call to be explained and this function, because many libc
functions will alter the value of errno.
initval The original initval, exactly as passed to the eventfd(2) system call.
flags The original flags, exactly as passed to the eventfd(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain
functions which do not supply a buffer in their argument list. This will be
overwritten by the next call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return buffer across all
threads, and many other functions in this library.
Example: This function is intended to be used in a fashion similar to the following
example:
int result = eventfd(initval, flags);
if (result < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_eventfd(err, initval, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_eventfd_or_die(3)
function.
explain_message_eventfd
void explain_message_eventfd(char *message, int message_size, unsigned int initval, int
flags);
The explain_message_eventfd function is used to obtain an explanation of an error returned
by the eventfd(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
The errno global variable will be used to obtain the error value to be decoded.
message The location in which to store the returned message. If a suitable message return
buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
initval The original initval, exactly as passed to the eventfd(2) system call.
flags The original flags, exactly as passed to the eventfd(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
int result = eventfd(initval, flags);
if (result < 0)
{
char message[3000];
explain_message_eventfd(message, sizeof(message), initval, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_eventfd_or_die(3)
function.
explain_message_errno_eventfd
void explain_message_errno_eventfd(char *message, int message_size, int errnum, unsigned
int initval, int flags);
The explain_message_errno_eventfd function is used to obtain an explanation of an error
returned by the eventfd(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
message The location in which to store the returned message. If a suitable message return
buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
errnum The error value to be decoded, usually obtained from the errno global variable
just before this function is called. This is necessary if you need to call any
code between the system call to be explained and this function, because many libc
functions will alter the value of errno.
initval The original initval, exactly as passed to the eventfd(2) system call.
flags The original flags, exactly as passed to the eventfd(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
int result = eventfd(initval, flags);
if (result < 0)
{
int err = errno;
char message[3000];
explain_message_errno_eventfd(message, sizeof(message), err, initval, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre‐packaged as the explain_eventfd_or_die(3)
function.
SEE ALSO
eventfd(2)
create a file descriptor for event notification
explain_eventfd_or_die(3)
create a file descriptor for event notification and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2009 Peter Miller
explain_eventfd(3)