[Toybox] setenv memory leak.

[enh]

why does toysh care? shells i've seen don't call setenv at all ---
they maintain an "environ" of their own for their children.

On Mon, Apr 8, 2019 at 11:42 AM Rob Landley <rob at landley.net> wrote:
>
> I'm inching towards reopening the toysh can of worms, and last time I opened it
> there was a problem with environment variable memory leaking in libc:
>
>   https://landley.net/notes-2006.html#24-10-2006
>
> Over the years I griped about this to Rich Felker, who fixed it in musl:
>
>   http://git.musl-libc.org/cgit/musl/tree/src/env/setenv.c
>
> But bionic still leaks each entry when you replace it:
>
>
> https://android.googlesource.com/platform/bionic/+/refs/heads/master/libc/upstream-openbsd/lib/libc/stdlib/setenv.c
>
> Meaning if you do:
>
>   for (i = 0; i<999999999; i++) setenv("this", "that", 1);
>
> It'll leak 9 gigabytes.
>
> This seems suboptimal, and is bad for long-running shell scripts.
>
> I'm also trying to redo the tar "command mode" (does anyone _use_ this? It was
> submitted so I _assume_ so but I've never encountered it in the wild) to use
> nommu-friendly xpopen_both() and the _easy_ way is to just set the environment
> variables in the host before the vfork() but that's resetting the same variables
> an aribtrary number of times and if libc can't free the variable memory...
>
> Rob
>
> P.S. I can do it myself with putenv() or my own direct environ() manipulation
> but that's not my first choice? Nor is rewriting xpopen() to have a callback
> doing arbitrary stuff in the vfork context before it execs, kinda defeats the
> point of that function...
>
> P.P.S. I honestly don't care if glibc gets this right or I'd have poked them
> about it sometime over the past 15 years. If they can't gnu/do the basic "wait,
> how does this work and what happens if" stuff a civilian like me does in passing
> that's _their_ gnu/problem.
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