explain_vsprintf(3)

💖 explain_vsprintf — bestie edition 💖

okay so like, this is the page for explain_vsprintf(3) from the Library Functions Manual, and it's basically the glow-up your error messages have been waiting for ✨

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🦋 NAME 🦋

explain_vsprintf — no cap, this explains vsprintf(3) errors 💅

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🌸 SYNOPSIS 🌸

#include <libexplain/vsprintf.h>
const char *explain_vsprintf(char *data, const char *format, va_list
ap);
const char *explain_errno_vsprintf(int errnum, char *data, const char
*format, va_list ap);
void explain_message_vsprintf(char *message, int message_size, char
*data, const char *format, va_list ap);
void explain_message_errno_vsprintf(char *message, int message_size, int
errnum, char *data, const char *format, va_list ap);

four whole functions, four whole vibes, we love to see it 🫶

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✨ DESCRIPTION ✨

okay so listen. these functions? they're literally here to hand you explanations for errors that the vsprintf(3) system call returns. it's giving "your code messed up and we're gonna tell you why" energy 💀

💜 explain_vsprintf

const char *explain_vsprintf(char *data, const char *format, va_list
ap);

so explain_vsprintf is the one you call to get an explanation of an error that came back from the vsprintf(3) system call. the least the message will contain is the value of strerror(errno), but bestie, usually it does so much better and tells you the underlying cause in way more detail. it ate, honestly 👑

the errno global variable is what gets used to grab the error value that needs decoding.

• data — the original data, exactly as passed to the vsprintf(3) system call. like, don't change it, don't spice it up, just pass it through fr fr
• format — the original format, exactly as passed to the vsprintf(3) system call
• ap — the original ap, exactly as passed to the vsprintf(3) system call

Returns:

the message explaining the error. this message buffer is shared by all libexplain functions that don't supply a buffer in their argument list. it will be overwritten by the next call to any libexplain function that shares this buffer — including other threads. so like, screenshot it fast bestie, it's not sticking around 📸

Note: this function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. not me warning you twice 💀

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

errno = 0;
int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    fprintf(stderr, "%s\n", explain_vsprintf(data, format, ap));
    exit(EXIT_FAILURE);
}

and the above code example is available pre-packaged as the explain_vsprintf_or_die(3) function. iconic, convenient, we stan 🎀

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🌈 explain_errno_vsprintf

const char *explain_errno_vsprintf(int errnum, char *data, const char
*format, va_list ap);

explain_errno_vsprintf is here to obtain an explanation of an error returned by the vsprintf(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. lowkey overachiever behavior 💅

• 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. like, errno is fickle bestie, it changes its mind constantly 😭
• data — the original data, exactly as passed to the vsprintf(3) system call
• format — the original format, exactly as passed to the vsprintf(3) system call
• ap — the original ap, exactly as passed to the vsprintf(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 = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_vsprintf(err, data,
    format, ap));
    exit(EXIT_FAILURE);
}

the above code example is available pre-packaged as the explain_vsprintf_or_die(3) function. slay 🦋

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🎀 explain_message_vsprintf

void explain_message_vsprintf(char *message, int message_size, char
*data, const char *format, va_list ap);

explain_message_vsprintf obtains an explanation of an error returned by the vsprintf(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. it's giving thorough ✨

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. ooh she's safe, she's careful, she's considerate 👑
• 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 vsprintf(3) system call
• format — the original format, exactly as passed to the vsprintf(3) system call
• ap — the original ap, exactly as passed to the vsprintf(3) system call

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

errno = 0;
int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    char message[3000];
    explain_message_vsprintf(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_vsprintf_or_die(3) function. main character energy fr fr 💜

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🧚 explain_message_errno_vsprintf

void explain_message_errno_vsprintf(char *message, int message_size, int
errnum, char *data, const char *format, va_list ap);

explain_message_errno_vsprintf is used to obtain an explanation of an error returned by the vsprintf(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 vsprintf(3) system call
• format — the original format, exactly as passed to the vsprintf(3) system call
• ap — the original ap, exactly as passed to the vsprintf(3) system call

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

errno = 0;
int result = vsprintf(data, format, ap);
if (result < 0 && errno != 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_vsprintf(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_vsprintf_or_die(3) function. periodt 💅

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🌟 SEE ALSO 🌟

• vsprintf(3) — formatted output conversion
• explain_vsprintf_or_die(3) — formatted output conversion and report errors

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👑 COPYRIGHT 👑

this is libexplain version 1.4, and the copyright is held by Copyright (C) 2010 Peter Miller.

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and that's the whole page bestie!! 🥳 no cap, you now know explain_vsprintf(3) inside and out. go forth, decode those errors, be the thread-safe queen you were always meant to be 💖🌸✨🦋🎀🫶🔥💜🌈⭐👑