From 4c7d82f1f11a3e122befccde505a1dc4519a22e7 Mon Sep 17 00:00:00 2001
From: Pádraig Brady <P@draigBrady.com>
Date: Thu, 14 Jan 2016 14:21:53 +0000
Subject: tests: simplify invalid signal determination for kill -l

* src/operand2sig.c (operand2sig): Add a detailed comment explaining
why we validate even very large shell exit status values.
* tests/misc/kill.sh: Add a test case for the ksh scheme.
Simplify the INVALID signal number determination which also avoids
a false failure on systems like FreeBSD 10 with incomplete
signal list (caused by inaccurate NSIG).
---
 src/operand2sig.c  | 11 +++++++++++
 tests/misc/kill.sh | 11 ++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/operand2sig.c b/src/operand2sig.c
index a9fede54b..62039db28 100644
--- a/src/operand2sig.c
+++ b/src/operand2sig.c
@@ -39,6 +39,17 @@ operand2sig (char const *operand, char *signame)
 
   if (ISDIGIT (*operand))
     {
+      /* Note we don't put a limit on the maximum value passed,
+         because we're checking shell $? values here, and ksh for
+         example will add 256 to the signal value, thus being wider
+         than the number of WEXITSTATUS bits.
+         We could validate that values were not above say
+         ((WEXITSTATUS (~0) << 1) + 1), which would cater for ksh.
+         But some shells may use other adjustments in future to be
+         (forward) compatible with systems that support
+         wider exit status values as discussed at
+         http://austingroupbugs.net/view.php?id=947  */
+
       char *endp;
       long int l = (errno = 0, strtol (operand, &endp, 10));
       int i = l;
diff --git a/tests/misc/kill.sh b/tests/misc/kill.sh
index 27d550ec8..779ce3e8f 100755
--- a/tests/misc/kill.sh
+++ b/tests/misc/kill.sh
@@ -49,10 +49,15 @@ env kill -t TERM HUP || fail=1
 SIGTERM=$(env kill -l HUP TERM | tail -n1) || fail=1
 test $(env kill -l "$SIGTERM") = TERM || fail=1
 
+# Verify we only consider the lower "signal" bits,
+# to support ksh which just adds 256 to the signal value
+STD_TERM_STATUS=$(expr "$SIGTERM" + 128)
+KSH_TERM_STATUS=$(expr "$SIGTERM" + 256)
+test $(env kill -l $STD_TERM_STATUS $KSH_TERM_STATUS | uniq) = TERM || fail=1
+
 # Verify invalid signal spec is diagnosed
-SIGINVAL=$(env kill -t | tail -n1 | cut -f1 -d' ')
-SIGINVAL=$(expr "$SIGINVAL" + 1)
-returns_ 1 env kill -l "$SIGINVAL" 0 || fail=1
+returns_ 1 env kill -l -1 || fail=1
+returns_ 1 env kill -l -1 0 || fail=1
 returns_ 1 env kill -l INVALID TERM || fail=1
 
 Exit $fail
-- 
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