check_sub_overflow(9)

💅 check_sub_overflow(9)

okay bestie so you're in the Kernel API Manual and you clicked on check_sub_overflow — welcome, you're gonna do great, this one's actually iconic ✨

🌸 NAME

check_sub_overflow — does subtraction, but like... with overflow checking 🎀

✨ SYNOPSIS

check_sub_overflow (a , b , d );

🦋 ARGUMENTS

• a — the minuend; it's the value you're subtracting from 🫶
• b — the subtrahend; the value you're taking away from a, no cap
• d — a pointer, and it's where the difference gets stored 💾

👑 DESCRIPTION

So it literally returns true on wrap-around and false otherwise. That's the whole vibe check 🔥

And here's the part that matters, bestie: *d holds the results of the attempted subtraction, regardless of whether wrap-around occurred. Like, even if things went sideways, the answer still lands in *d. She doesn't gatekeep 😭💖

🌈 SEE ALSO

The kernel file ./include/linux/overflow.h — go say hi, she's the source of truth 📁✨

Then the whole friend group:

• check_add_overflow(9)
• wrapping_add(9)
• wrapping_assign_add(9)
• wrapping_sub(9)
• wrapping_assign_sub(9)
• check_mul_overflow(9)
• wrapping_mul(9)
• check_shl_overflow(9)
• overflows_type(9)
• range_overflows(9)
• range_overflows_t(9)
• range_end_overflows(9)
• range_end_overflows_t(9)
• castable_to_type(9)
• size_mul(9)
• size_add(9)
• size_sub(9)
• array_size(9)
• array3_size(9)
• flex_array_size(9)
• struct_size(9)
• struct_size_t(9)
• struct_offset(9)
• __DEFINE_FLEX(9)
• _DEFINE_FLEX(9)
• DEFINE_RAW_FLEX(9)
• DEFINE_FLEX(9)
• STACK_FLEX_ARRAY_SIZE(9)
• typeof_flex_counter(9)
• overflows_flex_counter_type(9)
• __set_flex_counter(9)

okay that's the whole page, you ate that 🍓 this one lives in ./include/linux, dated October 2026, and it's filed under check_sub_overflow(9) — mwah, go write some overflow-safe code, i'm obsessed 💜🧚