struct_size_t(9)

✨ NAME ✨

okay so bestie, welcome to struct_size_t(9) from the Kernel API Manual 💖 — this is the little helper whose whole gig is: calculate size of structure with trailing flexible array. yes, it’s giving flexible-array math with main character energy 🎀.

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🌸 SYNOPSIS 🌸

struct_size_t (type , member , count );

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🎀 ARGUMENTS 🎀

• type — structure type name. like, the actual type bestie, no cap.
• member — name of the array member. the flexible-array member in question 💅.
• count — number of elements in the array. how many little elements are living in there 🫶.

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💜 DESCRIPTION 💜

so it calculates size of memory needed for structure type followed by an array of count number of member elements — literally the whole package, structure plus trailing array, sized correctly ✨.

lowkey though: prefer using struct_size when possible instead, because that keeps calculations associated with a specific instance variable of type type — and that association is kind of a big deal, iykyk 🧚.

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🌈 RETURN 🌈

it returns the number of bytes needed, or SIZE_MAX on overflow 😭. overflow said “not today,” and honestly? valid.

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🦋 SEE ALSO 🦋

the Kernel file for all this overflow math is ./include/linux/overflow.h — and the whole squad is here: check_add_overflow(9), wrapping_add(9), wrapping_assign_add(9), check_sub_overflow(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_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) 💖.

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okay bye bestie 💋 — source/version is ./include/linux, date is October 2026, and this struct_size_t(9) page is officially wrapped. go size those flexible arrays with main character energy 🌈👑.