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Merge pull request #20489 from jpalus/memory-alignment

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memory: fix memory alignment for dynamic allocation
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bfredl 2022-10-31 17:10:13 +01:00 committed by GitHub
commit bf3cbee630
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2 changed files with 23 additions and 15 deletions
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36
src/nvim/memory.c
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@ -6,6 +6,7 @@
#include <assert.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include "nvim/api/extmark.h"
@ -576,41 +577,48 @@ void alloc_block(Arena *arena)
blk->prev = prev_blk;
}
static size_t arena_align_offset(uint64_t off)
{
return ((off + (ARENA_ALIGN - 1)) & ~(ARENA_ALIGN - 1));
}
/// @param arena if NULL, do a global allocation. caller must then free the value!
/// @param size if zero, will still return a non-null pointer, but not a unique one
/// @param size if zero, will still return a non-null pointer, but not a usable or unique one
void *arena_alloc(Arena *arena, size_t size, bool align)
{
if (!arena) {
return xmalloc(size);
}
if (align) {
arena->pos = (arena->pos + (ARENA_ALIGN - 1)) & ~(ARENA_ALIGN - 1);
if (!arena->cur_blk) {
alloc_block(arena);
}
if (arena->pos + size > arena->size || !arena->cur_blk) {
size_t alloc_pos = align ? arena_align_offset(arena->pos) : arena->pos;
if (alloc_pos + size > arena->size) {
if (size > (ARENA_BLOCK_SIZE - sizeof(struct consumed_blk)) >> 1) {
// if allocation is too big, allocate a large block with the requested
// size, but still with block pointer head. We do this even for
// arena->size / 2, as there likely is space left for the next
// small allocation in the current block.
if (!arena->cur_blk) {
// to simplify free-list management, arena->cur_blk must
// always be a normal, ARENA_BLOCK_SIZE sized, block
alloc_block(arena);
}
arena_alloc_count++;
char *alloc = xmalloc(size + sizeof(struct consumed_blk));
size_t hdr_size = sizeof(struct consumed_blk);
size_t aligned_hdr_size = (align ? arena_align_offset(hdr_size) : hdr_size);
char *alloc = xmalloc(size + aligned_hdr_size);
// to simplify free-list management, arena->cur_blk must
// always be a normal, ARENA_BLOCK_SIZE sized, block
struct consumed_blk *cur_blk = (struct consumed_blk *)arena->cur_blk;
struct consumed_blk *fix_blk = (struct consumed_blk *)alloc;
fix_blk->prev = cur_blk->prev;
cur_blk->prev = fix_blk;
return (alloc + sizeof(struct consumed_blk));
return alloc + aligned_hdr_size;
} else {
alloc_block(arena);
alloc_block(arena); // resets arena->pos
alloc_pos = align ? arena_align_offset(arena->pos) : arena->pos;
}
}
char *mem = arena->cur_blk + arena->pos;
arena->pos += size;
char *mem = arena->cur_blk + alloc_pos;
arena->pos = alloc_pos + size;
return mem;
}

2
src/nvim/memory.h
View File

@ -45,7 +45,7 @@ typedef struct consumed_blk {
struct consumed_blk *prev;
} *ArenaMem;
#define ARENA_ALIGN sizeof(void *)
#define ARENA_ALIGN MAX(sizeof(void *), sizeof(double))
typedef struct {
char *cur_blk;