From 3e3f6b0f12dd846956e388b27c6afa749f9651bf Mon Sep 17 00:00:00 2001
From: Martijn Dekker <martijn@inlv.org>
Date: Thu, 18 Jun 2020 02:48:51 +0200
Subject: [PATCH] Restore #22 'unset -f' fix minus segfault (re: b7932e87,
 97511748)

Applying the fix for 'unset -f' exposed a crashing bug in lookup()
in sh/nvdisc.c, which is the function for looking up discipline
functions. This is what caused tests/variables.sh to crash.
Ref.: https://github.com/ksh93/ksh/issues/23#issuecomment-645699614

src/cmd/ksh93/sh/nvdisc.c: lookup():
- To avoid segfault, check that the function pointer nq->nvalue.rp
  is actually set before checking if nq->nvalue.rp->running==1.

src/cmd/ksh93/sh/xec.c,
src/cmd/ksh93/tests/functions.sh:
- Uncomment the 'unset -f' fix from b7932e87.

Resolves #21 (again).
---
 NEWS                             | 8 ++++++++
 src/cmd/ksh93/sh/nvdisc.c        | 2 +-
 src/cmd/ksh93/sh/xec.c           | 5 -----
 src/cmd/ksh93/tests/functions.sh | 2 --
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/NEWS b/NEWS
index 28dc7a2c5..41464aa3b 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,14 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2020-06-17:
+
+- A bug in 'unset -f' was fixed that prevented shell functions from
+  unsetting themselves while they were running. A POSIX function no longer
+  crashes when doing so, and a KornShell-style function no longer silently
+  ignores an 'unset -f' on itself. A function of either form now continues
+  running after unsetting itself, and is removed at the end of the run.
+
 2020-06-16:
 
 - Passing the '-d' flag to the read builtin will no longer cause the '-r'
diff --git a/src/cmd/ksh93/sh/nvdisc.c b/src/cmd/ksh93/sh/nvdisc.c
index d054cc4e4..927db34de 100644
--- a/src/cmd/ksh93/sh/nvdisc.c
+++ b/src/cmd/ksh93/sh/nvdisc.c
@@ -417,7 +417,7 @@ static char*	lookup(Namval_t *np, int type, Sfdouble_t *dp,Namfun_t *handle)
 	}
 	if(bp== &block)
 		block_done(bp);
-	if(nq && nq->nvalue.rp->running==1)
+	if(nq && nq->nvalue.rp && nq->nvalue.rp->running==1)
 	{
 		nq->nvalue.rp->running=0;
 		_nv_unset(nq,0);
diff --git a/src/cmd/ksh93/sh/xec.c b/src/cmd/ksh93/sh/xec.c
index d2e660820..6bb4355eb 100644
--- a/src/cmd/ksh93/sh/xec.c
+++ b/src/cmd/ksh93/sh/xec.c
@@ -3505,16 +3505,11 @@ static void sh_funct(Shell_t *shp,Namval_t *np,int argn, char *argv[],struct arg
 	nv_putval(SH_PATHNAMENOD,shp->st.filename,NV_NOFREE);
 	shp->pipepid = pipepid;
 	np->nvalue.rp->running  -= 2;
-/*
- * TODO: fix https://github.com/ksh93/ksh/issues/21
- * Following causes a memory fault in: bin/shtests -p variables
- *
 	if(np->nvalue.rp && np->nvalue.rp->running==1)
 	{
 		np->nvalue.rp->running = 0;
 		_nv_unset(np, NV_RDONLY);
 	}
-*/
 }
 
 /*
diff --git a/src/cmd/ksh93/tests/functions.sh b/src/cmd/ksh93/tests/functions.sh
index 7b081027c..ca51e026d 100755
--- a/src/cmd/ksh93/tests/functions.sh
+++ b/src/cmd/ksh93/tests/functions.sh
@@ -1253,12 +1253,10 @@ expect_status=0
 # When a function unsets itself, it should not fail to be unset
 $SHELL -c 'PATH=/dev/null; fn() { unset -f fn; true; }; fn' || err_exit 'unset of POSIX function in the calling stack fails'
 $SHELL -c 'PATH=/dev/null; function ftest { ftest2; }; function ftest2 { unset -f ftest; }; ftest' || err_exit 'unset of ksh function in the calling stack fails'
-: <<\end_disabled  # TODO: re-enable when https://github.com/ksh93/ksh/issues/21 is fixed
 $SHELL -c 'PATH=/dev/null; fn() { unset -f fn; true; }; fn; fn' 2> /dev/null
 [[ $? != 127 ]] && err_exit 'unset of POSIX function fails when it is still running'
 $SHELL -c 'PATH=/dev/null; function fn { unset -f fn; true; }; fn; fn' 2> /dev/null
 [[ $? != 127 ]] && err_exit 'unset of ksh function fails when it is still running'
-end_disabled
 
 # ======
 exit $((Errors<125?Errors:125))