explain_vasprintf(3)

💖 explain_vasprintf(3) 💖

okay bestie, welcome to explain_vasprintf, from the Library Functions Manual section (that's section 3, the "these are library calls" section, iykyk). This whole little family lives in libexplain and its whole entire job is to tell you why your vasprintf(3) call flopped instead of just leaving you on read with a cryptic errno. it's giving translator. it's giving emotional support for your error messages. 🫶

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✨ NAME ✨

explain_vasprintf — explain vasprintf(3) errors

like, it explains the errors. no cap, that's the whole name.

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🌸 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);

four functions. four little besties. each one hands you an explanation in a slightly different way depending on your vibe. 💅

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🦋 DESCRIPTION 🦋

These functions may be used to obtain explanations for errors returned by the vasprintf(3) system call. That's the mission statement, periodt.

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🎀 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. like it's not just gonna say "something went wrong", it's gonna say what went wrong and honestly? obsessed.

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. so like, be careful out there. 🙈

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. convenient much? 💖

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🌈 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. yes bestie, libc WILL snatch your errno out from under you if you let it, so grab it early.
• 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.

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💜 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. slay, you brought your own buffer, you're so responsible. ✨
• 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.

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⭐ 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.

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👑 SEE ALSO 👑

• vasprintf(3) — print to allocated string
• explain_vasprintf_or_die(3) — print to allocated string and report errors

like yes, go read those too, the crossover episode is real. 🌈

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💅 COPYRIGHT 💅

libexplain version 1.4 Copyright (C) 2013 Peter Miller

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and that's the whole page bestie!! go forth and explain your errors, you absolute icon 🦋✨

libexplain version 1.4, brought to you by Peter Miller, copyright (C) 2013 — mwah, thanks for the lore, we stan a documentation author. 💖