cc: [email protected]
Subject: Re: problem in ksh93
--------
> Hello,
>
> I found a problem in ksh93 where over-shifting in a function puts the
> interpreter into an indeterminate state.
> Adding *any* redirection to a function call seems to suppress the
> bailout and leads to undefined behavior.
>
> *Here is the test-case:**
> *<snip>
>
> #!/usr/bin/ksh
> some_func() {
> shift 10
> }
>
> for i in a b c d e f; do
> echo "read $i"
> [ "$i" != "c" ] && continue
> some_func 2>&1
> echo "$i = c"
> done
>
> </snip>
>
>
> *Output on ksh88 (Correct):**
> *read a
> read b
> read c
> test.ksh: shift: bad number
>
>
> *Output on ksh93 (Undefined behavior):**
> *read a
> read b
> read c
> test.ksh[4]: shift: 10: bad number
> c = c
> read d
> test.ksh[4]: shift: 10: bad number
> d = c
> read e
> test.ksh[4]: shift: 10: bad number
> e = c
> read f
> test.ksh[4]: shift: 10: bad number
> f = c
>
>
> *Output on ksh93 (Undefined behavior):**
> *Redirecting STDERR to /dev/null to show the program flow more clearly.
> read a
> read b
> read c
> c = c
> read d
> d = c
> read e
> e = c
> read f
> f = c
>
>
>
> *Here is the fix:**
> *--- a/src/cmd/ksh93/sh/xec.c Tue Jul 16 12:43:53 2013
> +++ b/src/cmd/ksh93/sh/xec.c Tue Jul 16 12:44:07 2013
> @@ -1572,7 +1572,7 @@
> unset_instance(nq,&node,&nr,mode);
> sh_funstaks(slp->slchild,-1);
> stkclose(slp->slptr);
> - if(jmpval > SH_JMPFUN)
> + if(jmpval > SH_JMPFUN || (io &&
> jmpval > SH_JMPIO) )
> siglongjmp(*shp->jmplist,jmpval);
> goto setexit;
> }
>
> I am also attaching the patch file with this email. Please let me know
> on the fix.
>
>
> Thanks,
> Vijay
>
Good catch. The patch is looks correct.
David Korn
[email protected]
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