MDEV-20425 Implement Boolean debug build option debug_assert

Commit 536215e3 in MariaDB Server 10.3.1
introduced the compiler flag (not cmake option) DBUG_ASSERT_AS_PRINTF
that converts DBUG_ASSERT in non-debug builds into printouts.

For debug builds, it could be useful to be able to convert DBUG_ASSERT
into a warning or error printout, to allow execution to continue.
This would allow debug builds to be used for reproducing hard failures
that occur with release builds.

my_assert: A Boolean flag (set by default), tied to the new option
debug_assert that is available on debug builds only.
When set, DBUG_ASSERT() will invoke assert(), like it did until now.
When unset, DBUG_ASSERT() will invoke fprintf(stderr, ...)
with the file name, line number and assertion expression.

include/my_dbug.h

 /* Copyright (c) 2000, 2010, Oracle and/or its affiliates. 
-   Copyright (C) 2000, 2017, MariaDB Corporation Ab
+   Copyright (C) 2000, 2019, 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
@@ -35,6 +35,7 @@ struct _db_stack_frame_ {
 };
 
 struct  _db_code_state_;
+extern MYSQL_PLUGIN_IMPORT my_bool my_assert;
 extern  my_bool _dbug_on_;
 extern  my_bool _db_keyword_(struct _db_code_state_ *, const char *, int);
 extern  int _db_explain_(struct _db_code_state_ *cs, char *buf, size_t len);
@@ -103,7 +104,10 @@ extern int (*dbug_sanity)(void);
 #define DBUG_END()  _db_end_ ()
 #define DBUG_LOCK_FILE _db_lock_file_()
 #define DBUG_UNLOCK_FILE _db_unlock_file_()
-#define DBUG_ASSERT(A) do { if (!(A)) { _db_flush_(); assert(A); }} while (0)
+#define DBUG_ASSERT(A) do { if (!(A)) { _db_flush_();                      \
+      if (my_assert) assert(A);                                            \
+      else fprintf(stderr, "%s:%d: assert: %s\n", __FILE__, __LINE__, #A); \
+}} while (0)
 #define DBUG_SLOW_ASSERT(A) DBUG_ASSERT(A)
 #define DBUG_ASSERT_EXISTS
 #define DBUG_EXPLAIN(buf,len) _db_explain_(0, (buf),(len))

include/my_global.h

 /*
    Copyright (c) 2001, 2013, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2017, MariaDB Corporation
+   Copyright (c) 2009, 2019, 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
@@ -1043,6 +1043,19 @@ typedef ulong		myf;	/* Type of MyFlags in my_funcs */
 #define reg16 register
 #endif
 
+/*
+  MYSQL_PLUGIN_IMPORT macro is used to export mysqld data
+  (i.e variables) for usage in storage engine loadable plugins.
+  Outside of Windows, it is dummy.
+*/
+#ifndef MYSQL_PLUGIN_IMPORT
+#if (defined(_WIN32) && defined(MYSQL_DYNAMIC_PLUGIN))
+#define MYSQL_PLUGIN_IMPORT __declspec(dllimport)
+#else
+#define MYSQL_PLUGIN_IMPORT
+#endif
+#endif
+
 #include <my_dbug.h>
 
 /* Some helper macros */
@@ -1169,19 +1182,6 @@ typedef struct { const char *dli_fname, dli_fbase; } Dl_info;
 #endif
 #endif /* !defined(__func__) */
 
-/* 
-  MYSQL_PLUGIN_IMPORT macro is used to export mysqld data
-  (i.e variables) for usage in storage engine loadable plugins.
-  Outside of Windows, it is dummy.
-*/
-#ifndef MYSQL_PLUGIN_IMPORT
-#if (defined(_WIN32) && defined(MYSQL_DYNAMIC_PLUGIN))
-#define MYSQL_PLUGIN_IMPORT __declspec(dllimport)
-#else
-#define MYSQL_PLUGIN_IMPORT
-#endif
-#endif
-
 /* Defines that are unique to the embedded version of MySQL */
 
 #ifdef EMBEDDED_LIBRARY

include/my_sys.h

 /* Copyright (c) 2000, 2013, Oracle and/or its affiliates.
-   Copyright (c) 2010, 2017, MariaDB Corporation.
+   Copyright (c) 2010, 2019, 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
@@ -267,6 +267,7 @@ extern ulong    my_sync_count;
 extern uint	mysys_usage_id;
 extern int32    my_file_opened;
 extern my_bool	my_init_done, my_thr_key_mysys_exists;
+extern MYSQL_PLUGIN_IMPORT my_bool my_assert;
 extern my_bool  my_assert_on_error;
 extern myf      my_global_flags;        /* Set to MY_WME for more error messages */
 					/* Point to current my_message() */

mysys/my_static.c

 /* Copyright (c) 2000, 2011, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2012, Monty Program Ab.
+   Copyright (c) 2009, 2019, 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
@@ -36,6 +36,9 @@ ulong           my_file_total_opened= 0;
 int		my_umask=0664, my_umask_dir=0777;
 
 myf             my_global_flags= 0;
+#ifndef DBUG_OFF
+my_bool         my_assert= 1;
+#endif
 my_bool         my_assert_on_error= 0;
 struct st_my_file_info my_file_info_default[MY_NFILE];
 uint   my_file_limit= MY_NFILE;

sql/mysqld.cc

@@ -7454,6 +7454,10 @@ struct my_option my_long_options[]=
    0, GET_INT, REQUIRED_ARG, 0, 0, 0, 0, 0, 0},
 #endif /* HAVE_REPLICATION */
 #ifndef DBUG_OFF
+  {"debug-assert", 0,
+   "Allow DBUG_ASSERT() to invoke assert()",
+   &my_assert, &my_assert,
+   0, GET_BOOL, OPT_ARG, 1, 0, 0, 0, 0, 0},
   {"debug-assert-on-error", 0,
    "Do an assert in various functions if we get a fatal error",
    &my_assert_on_error, &my_assert_on_error,