ntdll: Match Windows used block filling.

dlls/kernel32/tests/heap.c

@@ -3270,6 +3270,35 @@ static void test_heap_checks( DWORD flags )
     ret = HeapFree( GetProcessHeap(), 0, p );
     ok( ret, "HeapFree failed\n" );
 
+    if (flags & HEAP_FREE_CHECKING_ENABLED)
+    {
+        UINT *p32, tmp = 0;
+
+        size = 4 + 3;
+        p = pHeapAlloc( GetProcessHeap(), 0, size );
+        ok( !!p, "HeapAlloc failed\n" );
+        p32 = (UINT *)p;
+
+        ok( p32[0] == 0xbaadf00d, "got %#x\n", p32[0] );
+        memcpy( &tmp, p + size - 3, 3 );
+        ok( tmp != 0xadf00d, "got %#x\n", tmp );
+        memset( p, 0xcc, size );
+
+        size += 2 * 4;
+        p = pHeapReAlloc( GetProcessHeap(), 0, p, size );
+        ok( !!p, "HeapReAlloc failed\n" );
+        p32 = (UINT *)p;
+
+        ok( p32[0] == 0xcccccccc, "got %#x\n", p32[0] );
+        ok( p32[1] << 8 == 0xcccccc00, "got %#x\n", p32[1] );
+        ok( p32[2] == 0xbaadf00d, "got %#x\n", p32[2] );
+        memcpy( &tmp, p + size - 3, 3 );
+        ok( tmp != 0xadf00d, "got %#x\n", tmp );
+
+        ret = pHeapFree( GetProcessHeap(), 0, p );
+        ok( ret, "failed.\n" );
+    }
+
     p = HeapAlloc( GetProcessHeap(), 0, 37 );
     ok( p != NULL, "HeapAlloc failed\n" );
     memset( p, 0xcc, 37 );

dlls/ntdll/heap.c

@@ -139,7 +139,7 @@ C_ASSERT( sizeof(ARENA_LARGE) == 4 * BLOCK_ALIGN );
 #define BLOCK_TYPE_FREE        'F'
 #define BLOCK_TYPE_LARGE       'L'
 
-#define BLOCK_FILL_USED        0x55
+#define BLOCK_FILL_USED        0xbaadf00d
 #define BLOCK_FILL_TAIL        0xab
 #define BLOCK_FILL_FREE        0xfeeefeee
 
@@ -513,6 +513,7 @@ static inline void mark_block_tail( struct block *block, DWORD flags )
 static inline void initialize_block( struct block *block, SIZE_T old_size, SIZE_T size, DWORD flags )
 {
     char *data = (char *)(block + 1);
+    SIZE_T i;
 
     if (size <= old_size) return;
 
@@ -524,7 +525,8 @@ static inline void initialize_block( struct block *block, SIZE_T old_size, SIZE_
     else if (flags & HEAP_FREE_CHECKING_ENABLED)
     {
         valgrind_make_writable( data + old_size, size - old_size );
-        memset( data + old_size, BLOCK_FILL_USED, size - old_size );
+        i = ROUND_SIZE( old_size, sizeof(DWORD) - 1 ) / sizeof(DWORD);
+        for (; i < size / sizeof(DWORD); ++i) ((DWORD *)data)[i] = BLOCK_FILL_USED;
     }
 }