38024: Improve POSIX and native EXIT traps compatibility.

Allow a nested function trap to leave save and restore a POSIX
trap.

Still fails if the POSIX trap was defined in a function.

ChangeLog

@@ -1,3 +1,9 @@
+2016-02-25  Peter Stephenson  <p.stephenson@samsung.com>
+
+	* 38024: Src/signals.c, Test/C03traps.ztst: improve 37999 to
+	allow nested zsh-mode EXIT traps not to remove a POSIX EXIT
+	trap.
+
 2016-02-19  Daniel Shahaf  <d.s@daniel.shahaf.name>
 
 	* unposted: Etc/completion-style-guide: Clarify the term "variant".

Src/signals.c

@@ -920,9 +920,14 @@ removetrap(int sig)
      * Note that we save the trap here even if there isn't an existing
      * one, to aid in removing this one.  However, if there's
      * already one at the current locallevel we just overwrite it.
+     *
+     * Note we save EXIT traps based on the *current* setting of
+     * POSIXTRAPS --- so if there is POSIX EXIT trap set but
+     * we are in native mode it can be saved, replaced by a function
+     * trap, and then restored.
      */
     if (!dontsavetrap &&
-	(sig == SIGEXIT ? !exit_trap_posix : isset(LOCALTRAPS)) &&
+	(sig == SIGEXIT ? !isset(POSIXTRAPS) : isset(LOCALTRAPS)) &&
 	locallevel &&
 	(!trapped || locallevel > (sigtrapped[sig] >> ZSIG_SHIFT)))
 	dosavetrap(sig, locallevel);

Test/C03traps.ztst

@@ -419,6 +419,23 @@
 >end of program
 >EXIT TRAP TRIGGERED
 
+   (cd ..; $ZTST_exe -fc '
+     echo entering program
+     emulate sh -c '\''trap "echo POSIX exit trap triggered" EXIT'\''
+     fn() {
+        trap "echo native zsh function-local exit trap triggered" EXIT
+        echo entering native zsh function
+     }
+     fn
+     echo exiting program
+   ')
+0:POSX EXIT trap can have nested native mode EXIT trap
+>entering program
+>entering native zsh function
+>native zsh function-local exit trap triggered
+>exiting program
+>POSIX exit trap triggered
+
    (set -e
     printf "a\nb\n" | while read line
     do