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Re: [BUG] RETURN trap with -o functrace: infinite recursion on 'eval ret

From: Chet Ramey
Subject: Re: [BUG] RETURN trap with -o functrace: infinite recursion on 'eval return'
Date: Fri, 13 Apr 2018 21:49:49 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.7.0

On 4/10/18 5:56 AM, Martijn Dekker wrote:
> $ bash -o functrace -c 'fn() { eval "return"; }; trap "fn" RETURN; fn'
> Result: segfault due to infinite recursion.

Thanks for the report; I'll fix this.

> Even apart from this bug with 'eval return', the effect of '-o functrace'
> is a bit strange:
> $ bash -o functrace -c 'fn() { printf foo; fn2; };
>     fn2() { printf bar; fn3; };
>     fn3() { printf baz\\n; };
>     trap fn RETURN; fn'
> foobarbaz
> foobarbaz
> foobarbaz
> foobarbaz
> (I'd expect one 'foobarbaz', not four)
> It seems odd that the RETURN trap would be triggered while a RETURN trap
> action is still being executed. Might it be better to temporarily
> deactivate the effect of '-o functrace' while a RETURN trap action is being
> executed?

Well, trap handlers are recursive, in the sense that you can execute a trap
on signal X from a signal X trap handler. If the RETURN trap is inherited
by functions, and traps are recursive, wouldn't the bash behavior be the
logical thing to do? (Yes, I know there are problems with recursive signal
handler invocations in bash-4.4.)

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://tiswww.cwru.edu/~chet/

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