MDEV-29152: Assertion failed ... upon TO_CHAR with wrong argument

Item_func_tochar::check_arguments() didn't check if its arguments
each had one column. Failing to make this check and proceeding would
eventually cause either an assertion failure or the execution would
reach "MY_ASSERT_UNREACHABLE();" which would produce a crash with
a misleading stack trace.

* Fixed Item_func_tochar::check_arguments() to do the required check.

* Also fixed MY_ASSERT_UNREACHABLE() to terminate the program. Just
"executing" __builtin_unreachable() used to cause "undefined results",
which in my experience was a crash with corrupted stack trace.

include/my_compiler.h

@@ -40,7 +40,15 @@
 /* GNU C/C++ */
 #if defined __GNUC__
 # define MY_ALIGN_EXT
-# define MY_ASSERT_UNREACHABLE()   __builtin_unreachable()
+
+/*
+  __builtin_unreachable() removes the "statement may fall through" warning-as-
+  error when MY_ASSERT_UNREACHABLE() is used in "case xxx:" in switch (...)
+  statements.
+  abort() is there to prevent the execution from reaching the
+  __builtin_unreachable() as this may cause misleading stack traces.
+*/
+# define MY_ASSERT_UNREACHABLE()  { abort(); __builtin_unreachable(); }
 
 /* Microsoft Visual C++ */
 #elif defined _MSC_VER
@@ -88,7 +96,7 @@
 #endif
 
 #ifndef MY_ASSERT_UNREACHABLE
-# define MY_ASSERT_UNREACHABLE()  do { assert(0); } while (0)
+# define MY_ASSERT_UNREACHABLE()  do { abort(); } while (0)
 #endif
 
 /**

mysql-test/suite/compat/oracle/r/func_to_char.result

@@ -439,3 +439,10 @@ NULL
 NULL
 2021-01-24
 drop table t1,t2;
+set @local.sql_mode=@sql_mode;
+#
+# MDEV-29152: Assertion failed ... upon TO_CHAR with wrong argument
+#
+SELECT TO_CHAR((VALUES('2022-12-12','2020-10-10')));
+ERROR HY000: Illegal parameter data type row for operation 'to_char'
+SELECT TO_CHAR((STR_TO_DATE('2023-01-01', '%d-%m-%Y'), 'YYYY-MM-DD') );

mysql-test/suite/compat/oracle/t/func_to_char.test

@@ -224,3 +224,13 @@ select * from t2;
 drop table t1,t2;
 set @local.sql_mode=@sql_mode;
 
+--echo #
+--echo # MDEV-29152: Assertion failed ... upon TO_CHAR with wrong argument
+--echo #
+
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT TO_CHAR((VALUES('2022-12-12','2020-10-10')));
+
+--error ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATION
+SELECT TO_CHAR((STR_TO_DATE('2023-01-01', '%d-%m-%Y'), 'YYYY-MM-DD') );
+

sql/item_timefunc.h

@@ -996,7 +996,10 @@ class Item_func_tochar :public Item_str_func
 
   bool check_arguments() const override
   {
-    return check_argument_types_can_return_text(1, arg_count);
+    return
+      (args[0]->check_type_can_return_date(func_name_cstring()) &&
+       args[0]->check_type_can_return_time(func_name_cstring())) ||
+      check_argument_types_can_return_text(1, arg_count);
   }
 
 public: