Re: Memory continusely increase

[Eduardo Bustamante]

+ Adding Abhishek

Hi Chen and Abhishek, it seems you might work on the same team since
you sent the exact same bug report:

- http://lists.gnu.org/archive/html/bug-bash/2018-12/msg00059.html
- http://lists.gnu.org/archive/html/bug-bash/2018-12/msg00058.html
- http://lists.gnu.org/archive/html/bug-bash/2018-12/msg00057.html

On Wed, Dec 19, 2018 at 6:45 AM jake <chen.liu.opensource@gmail.com> wrote:
>
> Hi all,
>
> I did a test about run a bash scriplt never quit,but met a memory usage
> issue that cause used memory continuous increase.
> This issue was present in bash-3.2.x, bash-4.0.x, bash-4.1.x, bash-4.2.x,
> bash-4.3.x. However, This issue was disappeared in bash-4.4.0, I can't trace
> which patch fixed the issue or which new feature was introduced in
> bash-4.4.0.

These versions (3.2, 4.0, 4.1, 4.2 and 4.3) are fairly old. Any
particular reason you're not upgrading to 4.4 instead?

> Could someone help to tell me which part of changes in bash-4.4.0, that
> would be give me a direction backport code changes from bash-4.4 to
> bash-3.2.x and bash-4.3.x.

(...)

> while(true);do
>  while (true); do
>    ls > /dev/null
>  done
> done

My guess is that it's a memory leak in subshell creation. You don't
need that subshell by the way, the following should work just fine:

while :; do
 ...
done

The parenthesis are not only not needed, but they add overhead because
a new subshell is created every time.


Anyways, looking at the changelog for 4.4, it looks like it's going to
be time consuming to find / backport this, since there are many memory
leaks that were fixed:

$ grep -i leak ./CHANGES-4.4
c.  Fixed several memory leaks.
a.  Fixed a memory leak when processing ${!var[@]}.
i.  Fixed a memory leak in the code that removes duplicate history entries.
b.  Fixed a memory leak in programmable completion.
i.  Fixed a memory leak when processing declare commands that perform compound
s.  Fixed a memory leak that occurred when interrupting brace expansions
dd. Fixed a memory leak when creating local array variables and assigning to
p.  Fixed a potential file descriptor leak when dup2() fails while performing a
i.  Some memory leaks caused by signals interrupting filename completion have


I'll try to go through some of these changes later today to see if
anything evident comes up. I still recommend just upgrading to 4.4 if
you can though. Running outdated versions is never fun.