xmerl_sax_parser:stream/2 stack keeps growing until the VM is OOM

[leoliu]

Describe the bug
The stack_size of the process running xmerl_sax_parser:stream/2 keeps growing.

To Reproduce
Use xmerl_sax_parser:stream/2 on a large file and observe the stack growing by checking process_info(Pid, stack_size).

Expected behavior
I expect the stream parser to handle infinite stream without blowing up the stack.

Affected versions
Tested on 27.2 but seems all versions are affected.

Additional context
I used xmerl_sax_parser:stream/2 to parse the XML stream from an ejabberd server and noticed after a while the VM is killed by the OOM killer. After some inspection the process has a huge stack_size that keeps growing.

I also verified that removing the error handling in the first two clauses of xmerl_sax_parser_utf8:parse_content/4 and keeping just the cf/5 calls i.e. making it tail-recursive, the stack size is constant.

[lthor]

This is planned to fix in the next sprint.

[leoliu]

I wonder if a fix may be ready for OTP 27.3?

[dgud]

A guess based on Lars workload is no, but a PR might help

[lthor]

I plan to look at it during Februari, so it could be possible must check the exact date for code stop.

[leoliu]

Thanks for the replies. Sounds like a good plan. I locally modified xmerl to work around this bug but it’s hackish.

[lthor]

Hi,
the correction is pushed to maint and master so it will be delivered in OTP 27.3 (it will also be released in OTP 26 maintenance branch later).
In addition to fixing the tail recursion problem I also changed all old style catch in xmerl to try.

[leoliu]

Thank you. I can confirm the fix.