libexplain/poll.h File Reference

explain poll(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>

Go to the source code of this file.

Functions
int	explain_poll_or_die (struct pollfd *data, int data_size, int timeout)
int	explain_poll_on_error (struct pollfd *data, int data_size, int timeout)
const char *	explain_poll (struct pollfd *data, int data_size, int timeout) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_poll (int errnum, struct pollfd *data, int data_size, int timeout) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_poll (char *message, int message_size, struct pollfd *data, int data_size, int timeout)
void	explain_message_errno_poll (char *message, int message_size, int errnum, struct pollfd *data, int data_size, int timeout)

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Detailed Description

explain poll(2) errors

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

Definition in file poll.h.

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Function Documentation

const char* explain_errno_poll	(	int	errnum,
		struct pollfd *	data,
		int	data_size,
		int	timeout
	)

The explain_errno_poll function is used to obtain an explanation of an error returned by the poll(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.
data	The original data, exactly as passed to the poll(2) system call.
data_size	The original data_size, exactly as passed to the poll(2) system call.
timeout	The original timeout, exactly as passed to the poll(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 = poll(data, data_size, timeout);
 if (result < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_poll(err, data, data_size,
         timeout));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_poll_or_die function.

void explain_message_errno_poll	(	char *	message,
		int	message_size,
		int	errnum,
		struct pollfd *	data,
		int	data_size,
		int	timeout
	)

The explain_message_errno_poll function is used to obtain an explanation of an error returned by the poll(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.
data	The original data, exactly as passed to the poll(2) system call.
data_size	The original data_size, exactly as passed to the poll(2) system call.
timeout	The original timeout, exactly as passed to the poll(2) system call.

Example:

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

 int result = poll(data, data_size, timeout);
 if (result < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_poll(message, sizeof(message), err, data,
         data_size, timeout);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_poll_or_die function.

void explain_message_poll	(	char *	message,
		int	message_size,
		struct pollfd *	data,
		int	data_size,
		int	timeout
	)

The explain_message_poll function is used to obtain an explanation of an error returned by the poll(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.
data	The original data, exactly as passed to the poll(2) system call.
data_size	The original data_size, exactly as passed to the poll(2) system call.
timeout	The original timeout, exactly as passed to the poll(2) system call.

Example:

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

 int result = poll(data, data_size, timeout);
 if (result < 0)
 {
     char message[3000];
     explain_message_poll(message, sizeof(message), data, data_size,
         timeout);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_poll_or_die function.

const char* explain_poll	(	struct pollfd *	data,
		int	data_size,
		int	timeout
	)

The explain_poll function is used to obtain an explanation of an error returned by the poll(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:

data	The original data, exactly as passed to the poll(2) system call.
data_size	The original data_size, exactly as passed to the poll(2) system call.
timeout	The original timeout, exactly as passed to the poll(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 = poll(data, data_size, timeout);
 if (result < 0)
 {
     fprintf(stderr, "%s\n", explain_poll(data, data_size, timeout));
     exit(EXIT_FAILURE);
 }

The above code example is available pre\-packaged as the explain_poll_or_die function.

int explain_poll_on_error	(	struct pollfd *	data,
		int	data_size,
		int	timeout
	)

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

Parameters:

data	The data, exactly as to be passed to the poll(2) system call.
data_size	The data_size, exactly as to be passed to the poll(2) system call.
timeout	The timeout, exactly as to be passed to the poll(2) system call.

Returns:

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

Example:

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

 int result = explain_poll_on_error(data, data_size, timeout);
 if (result < 0)
 {
     ...cope with error
     ...no need to print error message
 }

int explain_poll_or_die	(	struct pollfd *	data,
		int	data_size,
		int	timeout
	)

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

Parameters:

data	The data, exactly as to be passed to the poll(2) system call.
data_size	The data_size, exactly as to be passed to the poll(2) system call.
timeout	The timeout, exactly as to be passed to the poll(2) system call.

Returns:

This function only returns on success, see poll(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_poll_or_die(data, data_size, timeout);