StdioClose with $STDERR_MERGED memory leak

[jvanegmond]

The following AutoIt code when run on my machine by AutoIt v3.3.15.0 leaks several MB of memory per minute:

#include <Constants.au3>

While 1
    $pid = Run("ping localhost","", @SW_HIDE, $STDERR_MERGED)
    ProcessWait($pid)
    StdioClose($pid)
    ProcessClose($pid)
    ProcessWaitClose($pid)
WEnd

Originally reported here ​https://www.autoitscript.com/forum/topic/177671-stdoutread-memory-problem-edit-and-stdioclose/

[Jpm]

If I understand well you just miss a StdIoClose($pid) at the right place
as suggested by Jos

[jvanegmond]

Jpm, the problem is solved. However, AutoIt methods should never leak memory. They should prevent the memory leak or catch the conditions where they can leak and return and set @error instead. Doing otherwise is unnecessarily confusing and placing the burden on end-users which we should not want.

In this particular case, because the problem only happens with $STDERR_MERGED defined, I would guess it is probably an oversight inside of StdioClose or ProcessClose for that particular case.

[anonymous]

Agree there is a bug there somewhere.
Firstly the posted script is what the helpfile also advertises and has a memory leak, but it seems there is also a leak when you comment the StdioClose()statement. Could it be that ProcessClose() isn't cleaning up when STDIO is used for the process?

Jos

[jvanegmond]

Replying to anonymous:

but it seems there is also a leak when you comment the StdioClose()statement. Could it be that ProcessClose() isn't cleaning up when STDIO is used for the process?

Interestingly, the only order which does seem to work is the exact one you posted on the forum where you call StdioClose after ProcessWaitClose. Any other order and it leaks memory.

[Jos]

Correct or the other option is to replace the StdioClose() by a loop that reads the STDIO buffer until it has read everything. This will also avoid the leaking.

Jos

[Jpm]

For me the StdIoClose() can do a definitive cleaning only if the process is really close so that normal it should be post after to have a complete cleaning
The Stream reading must be available by StdOutRead() or StdErrRead() after the process closing. So If you don't do it StdIoClose() will do it for you.

I hope I understand the AutoIt implementation. I leave to Jon the final answer

[Valik]

JP, the documentation clearly states that StdioClose() releases all resources. It shouldn't matter if the process is closed or not, AutoIt should internally close the handles and release any buffers.

It's been years since I wrote the STDIO code and I don't have access to it any longer (and it may have changed in the years since I left the project). I have an idea where the leak may be, though. Remember that when the buffer fills up the child program and AutoIt will deadlock. There's a pretty good chance I wrote the feature to always read the buffer and store the data internally to prevent the deadlock. I suspect it may be this internal buffer that's causing the problem. It's probably being dynamically allocated on each call which could theoretically cause an artificial inflation in the working set.

[Jpm]

Thanks Valik for the info just PM me if you want I PM you the actual code you re thinking about
Cheers

[Valik]

Sorry, JP. I'm not interested in looking at the code.

[Jpm]

Anyway thanks Valik for the info
Cheers

[Jpm]

Fix sent to Jon

[Jon]

Fixed by revision [12557] in version: 3.3.15.4