Use a typedef my_bool to improve compatibility across MySQL versions

MySQL 8.0 replaces my_bool with C99 bool. Earlier versions of MySQL had
a typedef to char. Gem users reported failures on big endian systems when
using C99 bool types with older MySQLs due to mismatched behavior.

ext/mysql2/extconf.rb

@@ -105,12 +105,17 @@ def add_ssl_defines(header)
 add_ssl_defines(mysql_h)
 have_struct_member('MYSQL', 'net.vio', mysql_h)
 have_struct_member('MYSQL', 'net.pvio', mysql_h)
+
 # These constants are actually enums, so they cannot be detected by #ifdef in C code.
 have_const('MYSQL_ENABLE_CLEARTEXT_PLUGIN', mysql_h)
 have_const('SERVER_QUERY_NO_GOOD_INDEX_USED', mysql_h)
 have_const('SERVER_QUERY_NO_INDEX_USED', mysql_h)
 have_const('SERVER_QUERY_WAS_SLOW', mysql_h)
 
+# my_bool is replaced by C99 bool in MySQL 8.0, but we want
+# to retain compatibility with the typedef in earlier MySQLs.
+have_type('my_bool', mysql_h)
+
 # This is our wishlist. We use whichever flags work on the host.
 # -Wall and -Wextra are included by default.
 wishlist = [

ext/mysql2/mysql2_ext.h

@@ -28,6 +28,14 @@ void Init_mysql2(void);
 #define RB_MYSQL_UNUSED
 #endif
 
+/* MySQL 8.0 replaces my_bool with C99 bool. Earlier versions of MySQL had
+ * a typedef to char. Gem users reported failures on big endian systems when
+ * using C99 bool types with older MySQLs due to mismatched behavior. */
+#ifndef HAVE_TYPE_MY_BOOL
+#include <stdbool.h>
+typedef bool my_bool;
+#endif
+
 #include <client.h>
 #include <statement.h>
 #include <result.h>