Bug #98854 session tracker
Submitted: 6 Mar 2020 10:57 Modified: 7 Mar 2020 0:45
Reporter: andy zhang Email Updates:
Status: Verified Impact on me:
Category:MySQL Server: Command-line Clients Severity:S3 (Non-critical)
Version:8.0, 5.7 OS:Any
Assigned to: CPU Architecture:Any
Tags: mysqltest

[6 Mar 2020 10:57] andy zhang
read_ok_ex() function in client.cc has problem on boundary check while doing the list_list reversion at the end.

The problem was discovered while I tried to introduce new session trackers, which could have multiple nodes for each command. The information was printed in reverted order.

The code snippet is like this

        if (info) {
          int itype;
          for (itype = SESSION_TRACK_BEGIN; itype < SESSION_TRACK_END;
<<<  It should be 
          for (itype = SESSION_TRACK_BEGIN; itype <= SESSION_TRACK_END;
               itype++) {
            if (info->info_list[itype].head_node) {
              info->info_list[itype].current_node =
                  info->info_list[itype].head_node =


How to repeat:
Not a direct case to report the problem.

Suggested fix:
In read_ok_ex(), change 

          for (itype = SESSION_TRACK_BEGIN; itype < SESSION_TRACK_END;
          for (itype = SESSION_TRACK_BEGIN; itype <= SESSION_TRACK_END;
[6 Mar 2020 13:46] MySQL Verification Team
Hi Mr. zhang,

Thank you for your bug report.

I have checked your analysis and came up to several conclusions.

First of all, this is a code that runs only on MS Windows, so I had to correct the entry to that field.

Second, your analysis of the loop checking condition is quite correct. Indeed, in other places in the code the '<=' conditions is applied.

Verified as reported.
[7 Mar 2020 0:45] andy zhang

Thanks for your reply.

I found the problem on my Linux environment. And I didn't try on MS windows. The problem is a common one. It affects both Windows and Linux, I think.
[9 Mar 2020 12:59] MySQL Verification Team
I agree. You are quite right.

Seemed to me that this is part of the shared memory code, but it is not.

Changed OS.