diff options
| -rw-r--r-- | src/spritecache.cpp | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/src/spritecache.cpp b/src/spritecache.cpp index 990f40726..1470522d2 100644 --- a/src/spritecache.cpp +++ b/src/spritecache.cpp @@ -306,8 +306,18 @@ void DupSprite(SpriteID old_spr, SpriteID new_spr) scnew->warned = false; } +/** + * S_FREE_MASK is used to mask-out lower bits of MemBlock::size + * If they are non-zero, the block is free. + * S_FREE_MASK has to ensure MemBlock is correctly aligned - + * it means 8B (S_FREE_MASK == 7) on 64bit systems! + */ +static const size_t S_FREE_MASK = sizeof(size_t) - 1; -#define S_FREE_MASK 1 +/* to make sure nobody adds things to MemBlock without checking S_FREE_MASK first */ +assert_compile(sizeof(MemBlock) == sizeof(size_t)); +/* make sure it's a power of two */ +assert_compile((sizeof(size_t) & (sizeof(size_t) - 1)) == 0); static inline MemBlock *NextBlock(MemBlock *block) { @@ -439,9 +449,9 @@ void *AllocSprite(size_t mem_req) { mem_req += sizeof(MemBlock); - /* Align this to an uint32 boundary. This also makes sure that the 2 least - * bits are not used, so we could use those for other things. */ - mem_req = Align(mem_req, sizeof(uint32)); + /* Align this to correct boundary. This also makes sure at least one + * bit is not used, so we can use it for other things. */ + mem_req = Align(mem_req, S_FREE_MASK + 1); for (;;) { MemBlock *s; |