MDEV-9021: MYSQLD SEGFAULTS WHEN BUILT USING --WITH-MAX-INDEXES=128

The bitmap implementation defines two template Bitmap classes. One
optimized for 64-bit (default) wide bitmaps while the other is used for
all other widths.

In order to optimize the computations, Bitmap<64> class has defined its
own member functions for bitmap operations, the other one, however,
relies on mysys' bitmap implementation (mysys/my_bitmap.c).

Issue 1:
In case of non 64-bit Bitmap class, intersect() wrongly reset the
received bitmap while initialising a new local bitmap structure
(bitmap_init() clears the bitmap buffer) thus, the received bitmap was
getting cleared.

Fixed by initializing the local bitmap structure by using a temporary
buffer and later copying the received bitmap to the initialised bitmap
structure.

Issue 2:
The non 64-bit Bitmap class had the Iterator missing which caused
compilation failure.

Also added a cmake variable to hold the MAX_INDEXES value when supplied
from the command prompt. (eg. cmake .. -DMAX_INDEXES=128U). Checks have
been put in place to trigger build failure if MAX_INDEXES value is
greater than 128.

Test modifications:
* Introduced include/have_max_indexes_[64|128].inc to facilitate
skipping of tests for which the output differs with different
MAX_INDEXES.

* Introduced include/max_indexes.inc which would get modified by cmake
to reflect the MAX_INDEXES value used to build the server. This file
simply sets an mtr variable '$max_indexes' to show the MAX_INDEXES
value, which will then be consumed by the above introduced include file.

* Some tests (portions), dependent on MAX_INDEXES value, have been moved
to separate test files.

1 files changed, 11 insertions, 3 deletions

diff --git a/mysys/my_bitmap.c b/mysys/my_bitmap.c
index 67c478659b5..0eaf1a88aa1 100644
--- a/mysys/my_bitmap.c
+++ b/mysys/my_bitmap.c
@@ -306,6 +306,12 @@ uint bitmap_set_next(MY_BITMAP *map)
 }
 
 
+/**
+  Set the specified number of bits in the bitmap buffer.
+
+  @param map         [IN]       Bitmap
+  @param prefix_size [IN]       Number of bits to be set
+*/
 void bitmap_set_prefix(MY_BITMAP *map, uint prefix_size)
 {
   uint prefix_bytes, prefix_bits, d;
@@ -319,11 +325,12 @@ void bitmap_set_prefix(MY_BITMAP *map, uint prefix_size)
   m+= prefix_bytes;
   if ((prefix_bits= prefix_size & 7))
   {
-    *m++= (1 << prefix_bits)-1;
-    prefix_bytes++;
+    *(m++)= (1 << prefix_bits)-1;
+    // As the prefix bits are set, lets count this byte too as a prefix byte.
+    prefix_bytes ++;
   }
   if ((d= no_bytes_in_map(map)-prefix_bytes))
-    bzero(m, d);
+    memset(m, 0, d);
 }
 
 
@@ -373,6 +380,7 @@ my_bool bitmap_is_clear_all(const MY_BITMAP *map)
   my_bitmap_map *data_ptr= map->bitmap;
   my_bitmap_map *end= map->last_word_ptr;
 
+  DBUG_ASSERT(map->n_bits > 0);
   for (; data_ptr < end; data_ptr++)
     if (*data_ptr)
       return FALSE;