libexplain/eventfd.h File Reference

explain eventfd(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
int	explain_eventfd_or_die (unsigned int initval, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
int	explain_eventfd_on_error (unsigned int initval, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_eventfd (unsigned int initval, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_eventfd (int errnum, unsigned int initval, int flags) LIBEXPLAIN_WARN_UNUSED_RESULT
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)

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Detailed Description

explain eventfd(2) errors

These functions may be used to obtain explanations for errors returned by the eventfd(2) system call.

Definition in file eventfd.h.

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Function Documentation

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(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 function.

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.

Parameters:

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 function.

int explain_eventfd_on_error	(	unsigned int	initval,
		int	flags
	)

The explain_eventfd_on_error function is used to call the eventfd(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_eventfd(3) function.

Parameters:

initval	The initval, exactly as to be passed to the eventfd(2) system call.
flags	The flags, exactly as to be passed to the eventfd(2) system call.

Returns:

The value returned by the wrapped eventfd(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 int result = explain_eventfd_on_error(initval, flags);
 if (result < 0)
 {
     ...cope with error
     ...no need to print error message
 }

int explain_eventfd_or_die	(	unsigned int	initval,
		int	flags
	)

The explain_eventfd_or_die function is used to call the eventfd(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_eventfd(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

Parameters:

initval	The initval, exactly as to be passed to the eventfd(2) system call.
flags	The flags, exactly as to be passed to the eventfd(2) system call.

Returns:

This function only returns on success, see eventfd(2) for more information. On failure, prints an explanation and exits, it does not return.

Example:

This function is intended to be used in a fashion similar to the following example:

 int result = explain_eventfd_or_die(initval, flags);

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(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 function.

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(errnum), 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.

Parameters:

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 function.