Provided by: libexplain-dev_1.4.D001-12_amd64 
NAME
explain_vasprintf - explain vasprintf(3) errors
SYNOPSIS
#include <libexplain/vasprintf.h>
const char *explain_vasprintf(char **data, const char *format, va_list ap);
const char *explain_errno_vasprintf(int errnum, char **data, const char *format, va_list
ap);
void explain_message_vasprintf(char *message, int message_size, char **data, const char
*format, va_list ap);
void explain_message_errno_vasprintf(char *message, int message_size, int errnum, char
**data, const char *format, va_list ap);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the vasprintf(3)
system call.
explain_vasprintf
const char *explain_vasprintf(char **data, const char *format, va_list ap);
The explain_vasprintf function is used to obtain an explanation of an error returned by
the vasprintf(3) 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 vasprintf(3) system call.
format The original format, exactly as passed to the vasprintf(3) system call.
ap The original ap, exactly as passed to the vasprintf(3) 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:
errno = 0;
int result = vasprintf(data, format, ap);
if (result < 0 || errno != 0)
{
fprintf(stderr, "%s\n", explain_vasprintf(data, format, ap));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_vasprintf_or_die(3)
function.
explain_errno_vasprintf
const char *explain_errno_vasprintf(int errnum, char **data, const char *format, va_list
ap);
The explain_errno_vasprintf function is used to obtain an explanation of an error returned
by the vasprintf(3) 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 vasprintf(3) system call.
format The original format, exactly as passed to the vasprintf(3) system call.
ap The original ap, exactly as passed to the vasprintf(3) 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:
errno = 0;
int result = vasprintf(data, format, ap);
if (result < 0 || errno != 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_vasprintf(err, data, format, ap));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_vasprintf_or_die(3)
function.
explain_message_vasprintf
void explain_message_vasprintf(char *message, int message_size, char **data, const char
*format, va_list ap);
The explain_message_vasprintf function is used to obtain an explanation of an error
returned by the vasprintf(3) 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 vasprintf(3) system call.
format The original format, exactly as passed to the vasprintf(3) system call.
ap The original ap, exactly as passed to the vasprintf(3) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
errno = 0;
int result = vasprintf(data, format, ap);
if (result < 0 || errno != 0)
{
char message[3000];
explain_message_vasprintf(message, sizeof(message), data, format, ap);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_vasprintf_or_die(3)
function.
explain_message_errno_vasprintf
void explain_message_errno_vasprintf(char *message, int message_size, int errnum, char
**data, const char *format, va_list ap);
The explain_message_errno_vasprintf function is used to obtain an explanation of an error
returned by the vasprintf(3) 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 vasprintf(3) system call.
format The original format, exactly as passed to the vasprintf(3) system call.
ap The original ap, exactly as passed to the vasprintf(3) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
errno = 0;
int result = vasprintf(data, format, ap);
if (result < 0 || errno != 0)
{
int err = errno;
char message[3000];
explain_message_errno_vasprintf(message, sizeof(message), err, data, format,
ap);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_vasprintf_or_die(3)
function.
SEE ALSO
vasprintf(3)
print to allocated string
explain_vasprintf_or_die(3)
print to allocated string and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2013 Peter Miller
explain_vasprintf(3)