libexplain/shmat.h File Reference

explain shmat(2) errors More...

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

Go to the source code of this file.

Functions
void *	explain_shmat_or_die (int shmid, const void *shmaddr, int shmflg) LIBEXPLAIN_WARN_UNUSED_RESULT
void *	explain_shmat_on_error (int shmid, const void *shmaddr, int shmflg) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_shmat (int shmid, const void *shmaddr, int shmflg) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_shmat (int errnum, int shmid, const void *shmaddr, int shmflg) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_shmat (char *message, int message_size, int shmid, const void *shmaddr, int shmflg)
void	explain_message_errno_shmat (char *message, int message_size, int errnum, int shmid, const void *shmaddr, int shmflg)

---

Detailed Description

explain shmat(2) errors

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

Definition in file shmat.h.

---

Function Documentation

const char* explain_errno_shmat	(	int	errnum,
		int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

The explain_errno_shmat function is used to obtain an explanation of an error returned by the shmat(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.
shmid	The original shmid, exactly as passed to the shmat(2) system call.
shmaddr	The original shmaddr, exactly as passed to the shmat(2) system call.
shmflg	The original shmflg, exactly as passed to the shmat(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:

 void *result = shmat(shmid, shmaddr, shmflg);
 if (!result)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_shmat(err, shmid, shmaddr,
         shmflg));
     exit(EXIT_FAILURE);
 }

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

void explain_message_errno_shmat	(	char *	message,
		int	message_size,
		int	errnum,
		int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

The explain_message_errno_shmat function is used to obtain an explanation of an error returned by the shmat(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.
shmid	The original shmid, exactly as passed to the shmat(2) system call.
shmaddr	The original shmaddr, exactly as passed to the shmat(2) system call.
shmflg	The original shmflg, exactly as passed to the shmat(2) system call.

Example:

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

 void *result = shmat(shmid, shmaddr, shmflg);
 if (!result)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_shmat(message, sizeof(message), err, shmid,
         shmaddr, shmflg);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

void explain_message_shmat	(	char *	message,
		int	message_size,
		int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

The explain_message_shmat function is used to obtain an explanation of an error returned by the shmat(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.
shmid	The original shmid, exactly as passed to the shmat(2) system call.
shmaddr	The original shmaddr, exactly as passed to the shmat(2) system call.
shmflg	The original shmflg, exactly as passed to the shmat(2) system call.

Example:

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

 void *result = shmat(shmid, shmaddr, shmflg);
 if (!result)
 {
     char message[3000];
     explain_message_shmat(message, sizeof(message), shmid, shmaddr, shmflg);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

const char* explain_shmat	(	int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

The explain_shmat function is used to obtain an explanation of an error returned by the shmat(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:

shmid	The original shmid, exactly as passed to the shmat(2) system call.
shmaddr	The original shmaddr, exactly as passed to the shmat(2) system call.
shmflg	The original shmflg, exactly as passed to the shmat(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:

 void *result = shmat(shmid, shmaddr, shmflg);
 if (!result)
 {
     fprintf(stderr, "%s\n", explain_shmat(shmid, shmaddr, shmflg));
     exit(EXIT_FAILURE);
 }

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

void* explain_shmat_on_error	(	int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

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

Parameters:

shmid	The shmid, exactly as to be passed to the shmat(2) system call.
shmaddr	The shmaddr, exactly as to be passed to the shmat(2) system call.
shmflg	The shmflg, exactly as to be passed to the shmat(2) system call.

Returns:

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

Example:

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

 void *result = explain_shmat_on_error(shmid, shmaddr, shmflg);
 if (!result)
 {
     ...cope with error
     ...no need to print error message
 }

void* explain_shmat_or_die	(	int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

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

Parameters:

shmid	The shmid, exactly as to be passed to the shmat(2) system call.
shmaddr	The shmaddr, exactly as to be passed to the shmat(2) system call.
shmflg	The shmflg, exactly as to be passed to the shmat(2) system call.

Returns:

This function only returns on success, see shmat(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:

 void *result = explain_shmat_or_die(shmid, shmaddr, shmflg);