Cleanup: Remove mem_block_t::magic_n and mem_block_validate()

Use of freed memory is better caught by AddressSanitizer,
especially with ASAN_POISON_MEMORY_REGION that is aliased
by MEM_NOACCESS and UNIV_MEM_FREE.

storage/innobase/include/mem0mem.h

@@ -287,13 +287,6 @@ mem_heap_printf(
 	const char*	format,	/*!< in: format string */
 	...) MY_ATTRIBUTE ((format (printf, 2, 3)));
 
-/** Checks that an object is a memory heap (or a block of it)
-@param[in]	heap	Memory heap to check */
-UNIV_INLINE
-void
-mem_block_validate(
-	const mem_heap_t*	heap);
-
 #ifdef UNIV_DEBUG
 /** Validates the contents of a memory heap.
 Asserts that the memory heap is consistent
@@ -308,7 +301,6 @@ mem_heap_validate(
 
 /** The info structure stored at the beginning of a heap block */
 struct mem_block_info_t {
-	ulint	magic_n;/* magic number for debugging */
 #ifdef UNIV_DEBUG
 	char	file_name[8];/* file name where the mem heap was created */
 	unsigned line;	/*!< line number where the mem heap was created */
@@ -343,9 +335,6 @@ struct mem_block_info_t {
 			otherwise, this is NULL */
 };
 
-#define MEM_BLOCK_MAGIC_N	764741555
-#define MEM_FREED_BLOCK_MAGIC_N	547711122
-
 /* Header size for a memory heap block */
 #define MEM_BLOCK_HEADER_SIZE	UT_CALC_ALIGN(sizeof(mem_block_info_t),\
 					      UNIV_MEM_ALIGNMENT)

storage/innobase/include/mem0mem.ic

 /*****************************************************************************
 
 Copyright (c) 1994, 2014, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -144,16 +144,6 @@ mem_block_get_start(mem_block_t* block)
 	return(block->start);
 }
 
-/** Checks that an object is a memory heap block
-@param[in]	block	Memory block to check. */
-UNIV_INLINE
-void
-mem_block_validate(
-	const mem_block_t*	block)
-{
-	ut_a(block->magic_n == MEM_BLOCK_MAGIC_N);
-}
-
 /** Allocates and zero-fills n bytes of memory from a memory heap.
 @param[in]	heap	memory heap
 @param[in]	n	number of bytes; if the heap is allowed to grow into
@@ -186,8 +176,6 @@ mem_heap_alloc(
 	byte*		buf;
 	ulint		free;
 
-	ut_d(mem_block_validate(heap));
-
 	block = UT_LIST_GET_LAST(heap->base);
 
 	n += REDZONE_SIZE;
@@ -230,8 +218,6 @@ mem_heap_get_heap_top(
 	mem_block_t*	block;
 	byte*		buf;
 
-	ut_d(mem_block_validate(heap));
-
 	block = UT_LIST_GET_LAST(heap->base);
 
 	buf = (byte*) block + mem_block_get_free(block);
@@ -321,8 +307,6 @@ mem_heap_get_top(
 	mem_block_t*	block;
 	byte*		buf;
 
-	ut_d(mem_block_validate(heap));
-
 	block = UT_LIST_GET_LAST(heap->base);
 
 	buf = (byte*) block + mem_block_get_free(block) - MEM_SPACE_NEEDED(n);
@@ -342,8 +326,6 @@ mem_heap_free_top(
 {
 	mem_block_t*	block;
 
-	ut_d(mem_block_validate(heap));
-
 	n += REDZONE_SIZE;
 
 	block = UT_LIST_GET_LAST(heap->base);
@@ -419,8 +401,6 @@ mem_heap_free(
 	mem_block_t*	block;
 	mem_block_t*	prev_block;
 
-	ut_d(mem_block_validate(heap));
-
 	block = UT_LIST_GET_LAST(heap->base);
 
 	if (heap->free_block) {
@@ -447,11 +427,7 @@ mem_heap_get_size(
 /*==============*/
 	mem_heap_t*	heap)	/*!< in: heap */
 {
-	ulint		size	= 0;
-
-	ut_d(mem_block_validate(heap));
-
-	size = heap->total_size;
+	ulint size = heap->total_size;
 
 	if (heap->free_block) {
 		size += UNIV_PAGE_SIZE;

storage/innobase/mem/mem0mem.cc

@@ -222,8 +222,6 @@ mem_heap_validate(
 		block != NULL;
 		block = UT_LIST_GET_NEXT(list, block)) {
 
-		mem_block_validate(block);
-
 		switch (block->type) {
 		case MEM_HEAP_DYNAMIC:
 			break;
@@ -278,7 +276,6 @@ mem_heap_create_block_func(
 	      || (type == MEM_HEAP_BUFFER + MEM_HEAP_BTR_SEARCH));
 
 	if (heap != NULL) {
-		mem_block_validate(heap);
 		ut_d(mem_heap_validate(heap));
 	}
 
@@ -320,7 +317,6 @@ mem_heap_create_block_func(
 	block->buf_block = buf_block;
 	block->free_block = NULL;
 
-	block->magic_n = MEM_BLOCK_MAGIC_N;
 	ut_d(ut_strlcpy_rev(block->file_name, file_name,
 			    sizeof(block->file_name)));
 	ut_d(block->line = line);
@@ -368,8 +364,6 @@ mem_heap_add_block(
 	mem_block_t*	new_block;
 	ulint		new_size;
 
-	ut_d(mem_block_validate(heap));
-
 	block = UT_LIST_GET_LAST(heap->base);
 
 	/* We have to allocate a new block. The size is always at least
@@ -422,8 +416,6 @@ mem_heap_block_free(
 
 	buf_block = static_cast<buf_block_t*>(block->buf_block);
 
-	mem_block_validate(block);
-
 	UT_LIST_REMOVE(heap->base, block);
 
 	ut_ad(heap->total_size >= block->len);
@@ -431,7 +423,6 @@ mem_heap_block_free(
 
 	type = heap->type;
 	len = block->len;
-	block->magic_n = MEM_FREED_BLOCK_MAGIC_N;
 
 	if (type == MEM_HEAP_DYNAMIC || len < UNIV_PAGE_SIZE / 2) {
 		ut_ad(!buf_block);