explain_mmap(3)

NAME
explain_mmap - explain mmap(2) errors

SYNOPSIS
#include <libexplain/mmap.h>

const char *explain_mmap(void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);
const char *explain_errno_mmap(int errnum, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);
void explain_message_mmap(char *message, int message_size, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);
void explain_message_errno_mmap(char *message, int message_size, int errnum, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

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

  explain_mmap
const char *explain_mmap(void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

The explain_mmap function is used to obtain an explanation of an error returned by the mmap(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.

data
    The original data, exactly as passed to the mmap(2) system call.

data_size
    The original data_size, exactly as passed to the mmap(2) system call.

prot
    The original prot, exactly as passed to the mmap(2) system call.

flags
    The original flags, exactly as passed to the mmap(2) system call.

fildes
    The original fildes, exactly as passed to the mmap(2) system call.

offset
    The original offset, exactly as passed to the mmap(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 = mmap(data, data_size, prot, flags, fildes, offset);
    if (!result)
    {
    fprintf(stderr, "%s\n", explain_mmap(data, data_size, prot, flags, fildes, offset));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_mmap_or_die(3) function.

  explain_errno_mmap
const char *explain_errno_mmap(int errnum, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

The explain_errno_mmap function is used to obtain an explanation of an error returned by the mmap(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.

data
    The original data, exactly as passed to the mmap(2) system call.

data_size
    The original data_size, exactly as passed to the mmap(2) system call.

prot
    The original prot, exactly as passed to the mmap(2) system call.

flags
    The original flags, exactly as passed to the mmap(2) system call.

fildes
    The original fildes, exactly as passed to the mmap(2) system call.

offset
    The original offset, exactly as passed to the mmap(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 = mmap(data, data_size, prot, flags, fildes, offset);
    if (!result)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_mmap(err, data, data_size, prot, flags, fildes, offset));
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_mmap_or_die(3) function.

  explain_message_mmap
void explain_message_mmap(char *message, int message_size, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

The explain_message_mmap function is used to obtain an explanation of an error returned by the mmap(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.

data
    The original data, exactly as passed to the mmap(2) system call.

data_size
    The original data_size, exactly as passed to the mmap(2) system call.

prot
    The original prot, exactly as passed to the mmap(2) system call.

flags
    The original flags, exactly as passed to the mmap(2) system call.

fildes
    The original fildes, exactly as passed to the mmap(2) system call.

offset
    The original offset, exactly as passed to the mmap(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    void *result = mmap(data, data_size, prot, flags, fildes, offset);
    if (!result)
    {
        char message[3000];
    explain_message_mmap(message, sizeof(message), data, data_size, prot, flags, fildes, offset);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_mmap_or_die(3) function.

  explain_message_errno_mmap
void explain_message_errno_mmap(char *message, int message_size, int errnum, void *data, size_t data_size, int prot, int flags, int fildes, off_t offset);

The explain_message_errno_mmap function is used to obtain an explanation of an error returned by the mmap(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.

data
    The original data, exactly as passed to the mmap(2) system call.

data_size
    The original data_size, exactly as passed to the mmap(2) system call.

prot
    The original prot, exactly as passed to the mmap(2) system call.

flags
    The original flags, exactly as passed to the mmap(2) system call.

fildes
    The original fildes, exactly as passed to the mmap(2) system call.

offset
    The original offset, exactly as passed to the mmap(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    void *result = mmap(data, data_size, prot, flags, fildes, offset);
    if (!result)
    {
        int err = errno;
        char message[3000];
    explain_message_errno_mmap(message, sizeof(message), err, data, data_size, prot, flags, fildes, offset);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

The above code example is available pre-packaged as the explain_mmap_or_die(3) function.

SEE ALSO

mmap(2)
    map file or device into memory

explain_mmap_or_die(3)
    map file or device into memory and report errors

COPYRIGHT
libexplain version 1.1
Copyright (C) 2010 Peter Miller