[PATCH v4 7/9] ntdll: Introduce a new BLOCK_FLAG_SPLIT heap block flag.

[Rémi Bernon]

From: Rémi Bernon

To avoid coalescing free LFH blocks until their owning thread is
detached.
---
 dlls/ntdll/heap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/dlls/ntdll/heap.c b/dlls/ntdll/heap.c
index 4904dd87544..b2f71316492 100644
--- a/dlls/ntdll/heap.c
+++ b/dlls/ntdll/heap.c
@@ -101,6 +101,7 @@ C_ASSERT( sizeof(struct block) == 8 );
 #define BLOCK_FLAG_PREV_FREE   0x02
 #define BLOCK_FLAG_FREE_LINK   0x03
 #define BLOCK_FLAG_LARGE       0x04
+#define BLOCK_FLAG_SPLIT       0x08 /* block is split and must not be coalesced */
 #define BLOCK_FLAG_USER_INFO   0x10 /* user flags up to 0xf0 */
 #define BLOCK_FLAG_USER_MASK   0xf0

@@ -779,7 +780,7 @@ static inline BOOL subheap_decommit( const struct heap *heap, SUBHEAP *subheap,
 static void block_init_used( struct block *block, ULONG flags, SIZE_T size )
 {
     block_set_type( block, BLOCK_TYPE_USED );
-    block_set_flags( block, 0, BLOCK_USER_FLAGS( flags ) );
+    block_set_flags( block, ~BLOCK_FLAG_SPLIT, BLOCK_USER_FLAGS( flags ) );
     block->tail_size = block_get_size( block ) - sizeof(*block) - size;
     initialize_block( block, 0, size, flags );
     mark_block_tail( block, flags );
@@ -851,7 +852,8 @@ static NTSTATUS heap_free_block( struct heap *heap, ULONG flags, struct block *b

if (category < ARRAY_SIZE(heap->stats) && heap->stats[category].live <= 0x10) heap->stats[category].live--;

-    if ((next = next_block( subheap, block )) && (block_get_flags( next ) & BLOCK_FLAG_FREE))
+    if ((next = next_block( subheap, block )) && (block_get_flags( next ) & BLOCK_FLAG_FREE) &&
+        !(block_get_flags( next ) & BLOCK_FLAG_SPLIT))
     {
         /* merge with next block if it is free */
         entry = (struct entry *)next;
@@ -1120,7 +1122,7 @@ static BOOL validate_free_block( const struct heap *heap, const SUBHEAP *subheap
         err = "invalid previous free block pointer";
     else if (!(block_get_flags( prev ) & BLOCK_FLAG_FREE) || block_get_type( prev ) != BLOCK_TYPE_FREE)
         err = "invalid previous free block header";
-    else if ((next = next_block( subheap, block )))
+    else if ((next = next_block( subheap, block )) && !(block_get_flags( block ) & BLOCK_FLAG_SPLIT))
     {
         if (!(block_get_flags( next ) & BLOCK_FLAG_PREV_FREE))
             err = "invalid next block flags";