MySQL Bugs: #10267: mysqltest, wrong number of loops when a script is sourced within a loop

Bug #10267	mysqltest, wrong number of loops when a script is sourced within a loop
Submitted:	29 Apr 2005 16:42	Modified:	1 Sep 2005 19:20
Reporter:	Matthias Leich	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Command-line Clients	Severity:	S3 (Non-critical)
Version:	4.1	OS:
Assigned to:	Magnus Blåudd	CPU Architecture:	Any

Description:
mysqltest performes a wrong number of loops, when I
have the following situation:
let $outer= <n>; # Number of outer loops, <n> >= 2
while ($outer)
{
  --source <inner script>
  dec $outer;
}

If I use the workaround
let $outer= <n>; # Number of outer loops, <n> >= 2
while ($outer)
{
  <inserted code of inner script>
  dec $outer;
}
the number of executed loops is correct.

Slightly edited protocol of my test case:

Test with script within outer while loop
----------------------------------------
2 = outer loop variable after while
     here is the sourced script
2 = outer loop variable before dec
1 = outer loop variable after dec
1 = outer loop variable after while
     here is the sourced script
1 = outer loop variable before dec
0 = outer loop variable after dec
     here is the sourced script  <------ This
                             should never happen

Test with expanded script within outer while loop
-------------------------------------------------
2 = outer loop variable after while
     here is the sourced script
2 = outer loop variable before dec
1 = outer loop variable after dec
1 = outer loop variable after while
     here is the sourced script
1 = outer loop variable before dec
0 = outer loop variable after dec

My environment:
   - Intel PC with Linux(SuSE 9.1)
   - MySQL compiled from source
        Version 5.0 ChangeSet@1.1914, 2005-04-29
        Version 4.1 ChangeSet@1.2214, 2005-04-28

BTW: It looks like this bug is old, because I found an 
        old MySQL 5.0.3-alpha-debug for pc-linux on i686 
        (Source distribution) on my box and it shows the
        same wrong behaviour.
        2005-01-08 18:12 ../libexec/mysqld
        2005-01-08 18:12 ../bin/mysqltest

How to repeat:
Please use the attached test case files 
ml60.test  and ml60i.sub 
  copy them to mysql-test/t
  touch r/ml60.result     # Produce a dummy file with 
                                   # expected results
  ./mysql-test-run ml60
  inspect r/ml60.reject    # The protocol of the execution.

sourced test script

Attachment: ml60i.sub (application/octet-stream, text), 53 bytes.

test case

Attachment: ml60.test (application/test, text), 881 bytes.

I have another testcase with nested scripts within a loop 
where mysqltest crashes.
I guess this crash is another representation of this bug.
# Sourcing of files within a while loop.
#     include/ml031.inc sources include/ml0311.inc
# The loops are harmless until $num exceeds 8 .
let $num= 9;
while ($num)
{
   SELECT 'In loop' AS "";
   --source include/ml031.inc
   dec $num;
}

GDB:      (I hope that I started gdb with the correct options.)
Core was generated by `/home/matthias/Arbeit/mysql-5.0/src-B/client/.libs/lt-mysqltest --no-defaults -'.
Program terminated with signal 11, Segmentation fault.
...
(gdb) bt
#0  0x403860db in getc () from /lib/tls/libc.so.6
#1  0x0804f6b6 in my_getc (file=0x0) at mysqltest.c:2050
#2  0x0804f828 in read_line (buf=0x8068b20 "SELECT 'Leaving        include/ml0311.inc' AS \"\"", size=131072)
    at mysqltest.c:2098
#3  0x0804fddb in read_query (q_ptr=0xbfffe228) at mysqltest.c:2260
#4  0x08053956 in main (argc=13, argv=0xbfffe2c4) at mysqltest.c:3770
(gdb)

Workaround 1: Alter mysqltest.c from
      #define MAX_INCLUDE_DEPTH 16    to 32.
      But this is no real bug fix, because the number of logical open files
      is independend of the number of loops and definitely below 16. 
Workaround 2: Alter the testscript and replace the while loop
      by the necessary number of 
      --source ....
      --source ....
      But that's bad testscript architecture :(

testscripts

Attachment: ml031.test (application/test, text), 320 bytes.

testscript

Attachment: ml031.inc (application/octet-stream, text), 117 bytes.

testscript

Attachment: ml0311.inc (application/octet-stream, text), 100 bytes.

Problem occurs becuse the dynamic array q_lines that contains a cache of already read lines are overwritten by the lines read from the sourced file.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/internals/28339

No changelog entry needed.