al_fixmul(3)

💅 al_fixmul(3) — Allegro 5 API ✨

okay bestie, so this one lives in the Library Functions Manual and it's part of the Allegro 5 API — yes, that Allegro, the game library one, she's iconic 🎮💖

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🌸 SYNOPSIS 🌸

#include <allegro5/allegro.h>

al_fixed al_fixmul(al_fixed x, al_fixed y);

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🦋 DESCRIPTION 🦋

So here's the tea 🍵 — a fixed point value can be multiplied or divided by a plain old integer using the normal * and / operators, no drama, no special function needed, she's lowkey self-sufficient like that.

But — and this is the main character plot twist — if you wanna multiply two fixed point values together? Nope. You literally cannot just slam a * between them. You must use this function. That's the whole vibe. al_fixmul is the only way. periodt. 💅

Now for the serious part, bestie, don't skip this 🫶: if an overflow happens, Allegro's errno gets set, and the maximum possible value gets returned instead. Cool cool cool — however 🌈, errno is not cleared if the operation succeeds. So if you're planning to actually test for overflow, you gotta call al_set_errno(0) before you call al_fixmul(3). Otherwise you're just out here checking stale errno energy and that's not giving what you think it's giving. 😭

⚠️ seriously, al_set_errno(0) first, or your overflow check is fake news fr fr

✨ Example ✨

al_fixed result;

/* This will put 30000 into `result'. */
result = al_fixmul(al_itofix(10), al_itofix(3000));

/* But this overflows, and sets errno. */
result = al_fixmul(al_itofix(100), al_itofix(3000));
assert(!al_get_errno());

see how the first one is all innocent and gives you a clean 30000, and the second one is out here overflowing and setting errno like it owns the place? that's the whole point of the example, bestie 🎀

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👑 RETURN VALUE 👑

Returns the clamped result of multiplying x by y — and it sets Allegro's errno to ERANGE if there was an overflow. so if you see ERANGE, you know exactly what went down. no cap. 🔥

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💀 SEE ALSO 💀

• al_fixadd(3)
• al_fixsub(3)
• al_fixdiv(3)
• al_get_errno(3)

go read al_get_errno(3) if you're gonna be doing that overflow-checking thing, iykyk 👀

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later bestie — this page came to you straight from the Allegro reference manual, page al_fixmul(3) 💜 stay fixed-point fabulous ✨