explain_errcode_getaddrinfo

The explain_errcode_getaddrinfo function is used to obtain an explanation of an error returned by the getaddrinfo(3) system call. The least the message will contain is the value of gai_strerror(errcode), but usually it will do much better, and indicate the underlying cause in more detail.

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

int errcode = getaddrinfo(node, service, hints, res);
if (errncode == GAI_SYSTEM)
    errcode = errno;
if (errcode)
{
    fprintf(stderr, "%s\n", explain_errcode_getaddrinfo(errcode,
        node, service, hints, res));
    exit(EXIT_FAILURE);
}

The above code example is available as the explain_getaddrinfo_or_die(3) function.

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.

node

The original node, exactly as passed to the getaddrinfo(3) system call.

service

The original service, exactly as passed to the getaddrinfo(3) system call.

hints

The original hints, exactly as passed to the getaddrinfo(3) system call.

res

The original res, exactly as passed to the getaddrinfo(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.

explain_message_errno_getaddrinfo

The explain_message_errno_getaddrinfo function may be used to obtain an explanation of an error returned by the getaddrinfo(3) 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.

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

int errcode = getaddrinfo(node, service, hints, res);
if (errnode == EAI_SYSTEM)
    errcode = errno;
if (errcode)
{
    char message[3000];
    explain_message_errcode_getaddrinfo(message, sizeof(message),
        errcode, node, service, hints, res);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre‐packaged as the explain_getaddrinfo_or_die(3) function.

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.

node

The original node, exactly as passed to the getaddrinfo(3) system call.

service

The original service, exactly as passed to the getaddrinfo(3) system call.

hints

The original hints, exactly as passed to the getaddrinfo(3) system call.

res

The original res, exactly as passed to the getaddrinfo(3) system call.