Bug#36027494 Add mtr test for my_print_stacktrace

Add an mtr test which is only inteded to be run manually:
  ./mtr --no-check-testcases print_stacktrace
Inspect output in var/log/msqld.1.err

Change-Id: Ia308592441df0e4a23a18c590df867a15882cbef

mysql-test/collections/disabled.def

@@ -62,6 +62,7 @@ component_keyring_file.mysql_ts_alter_encrypt_1 : BUG#29531106 - ATTACHABLE_TRX(
 # main suite tests
 main.ds_mrr-big @solaris : BUG#14168107 Test leads to timeout on Solaris on slow sparc servers.
 main.gtid_next_xa_binlog_off : BUG#33650776 Failure of XA COMMIT of prepared txn, can result in txn rollback
+main.print_stacktrace : Bug#36027494 Add mtr test for my_print_stacktrace
 
 # Disabled due to InnoDB issues
 

mysql-test/t/print_stacktrace.test

@@ -0,0 +1,12 @@
+# Run manually, to test output from my_print_stacktrace()
+# ./mtr --no-check-testcases print_stacktrace
+# inspect output in var/log/msqld.1.err
+
+--source include/have_debug.inc
+
+--disable_query_log
+SET GLOBAL debug='+d,print_stacktrace';
+SELECT CONCAT("Please inspect mysqld server log,",
+              " look for print_stacktrace.\n") as Hello;
+SET GLOBAL debug='-d,print_stacktrace';
+--enable_query_log

sql/item_strfunc.cc

@@ -69,6 +69,7 @@
 #include "my_md5_size.h"
 #include "my_rnd.h"  // my_rand_buffer
 #include "my_sqlcommand.h"
+#include "my_stacktrace.h"
 #include "my_sys.h"
 #include "my_systime.h"
 #include "myisampack.h"
@@ -1106,6 +1107,9 @@ String *Item_func_concat::val_str(String *str) {
     }
     if (tmp_value.append(*res)) return error_str();
   }
+  DBUG_EXECUTE_IF(
+      "print_stacktrace", fprintf(stderr, "Calling my_print_stacktrace\n");
+      my_print_stacktrace(nullptr, my_thread_stack_size); fflush(stderr););
   tmp_value.set_charset(collation.collation);
   return &tmp_value;
 }