From 7e26443627926bb3bcc88bd790190d5e4e0eda98 Mon Sep 17 00:00:00 2001 From: Tavian Barnes Date: Thu, 11 May 2023 10:38:23 -0400 Subject: config: Properly align flex_sizeof() --- src/config.h | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) (limited to 'src/config.h') diff --git a/src/config.h b/src/config.h index 4408feb..c6dcc1e 100644 --- a/src/config.h +++ b/src/config.h @@ -140,11 +140,12 @@ */ #define countof(array) (sizeof(array) / sizeof(0[array])) -// Lower bound on flex_sizeof() -#define BFS_FLEX_LB(type, member, length) (offsetof(type, member) + sizeof(((type *)NULL)->member[0]) * (length)) - -// Maximum macro for BFS_FLEX_SIZE() -#define BFS_FLEX_MAX(a, b) ((a) > (b) ? (a) : (b)) +/** + * Round up to a multiple of an alignment. + */ +static inline size_t align_ceil(size_t align, size_t size) { + return (size + align - 1) & ~(align - 1); +} /** * Computes the size of a struct containing a flexible array member of the given @@ -154,13 +155,23 @@ * The type of the struct containing the flexible array. * @param member * The name of the flexible array member. - * @param length + * @param count * The length of the flexible array. */ -#define flex_sizeof(type, member, length) \ - (sizeof(type) <= BFS_FLEX_LB(type, member, 0) \ - ? BFS_FLEX_LB(type, member, length) \ - : BFS_FLEX_MAX(sizeof(type), BFS_FLEX_LB(type, member, length))) +#define flex_sizeof(type, member, count) \ + flex_sizeof_impl(alignof(type), sizeof(type), offsetof(type, member), sizeof(((type *)NULL)->member[0]), count) + +static inline size_t flex_sizeof_impl(size_t align, size_t min, size_t offset, size_t size, size_t count) { + size_t ret = align_ceil(align, offset + size * count); + + // Make sure flex_sizeof(type, member, 0) >= sizeof(type), even if the + // type has more padding than necessary for alignment + if (min > align_ceil(align, offset) && ret < min) { + ret = min; + } + + return ret; +} /** * Initialize a variable, unless sanitizers would detect uninitialized uses. -- cgit v1.2.3