sh: Fix execution of multiple statements in a trap when evalskip is set

Before this fix, only the first statement of the trap was executed if
evalskip was set. This is for example the case when:
    o  "-e" is set for this shell
    o  a trap is set on EXIT
    o  a function returns 1 and causes the script to abort

Reviewed by:	jilles
MFC after:	2 weeks

3 files changed, 34 insertions, 2 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index ea23a9d..f4f69d9 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -75,7 +75,7 @@ __FBSDID("$FreeBSD$");
 
 
 int evalskip;			/* set if we are skipping commands */
-static int skipcount;		/* number of levels to skip */
+int skipcount;			/* number of levels to skip */
 MKINIT int loopnest;		/* current loop nesting level */
 int funcnest;			/* depth of function calls */
 static int builtin_flags;	/* evalcommand flags for builtins */
diff --git a/bin/sh/eval.h b/bin/sh/eval.h
index fba6f9a..724e157 100644
--- a/bin/sh/eval.h
+++ b/bin/sh/eval.h
@@ -60,6 +60,7 @@ void evalbackcmd(union node *, struct backcmd *);
 #define in_function()	funcnest
 extern int funcnest;
 extern int evalskip;
+extern int skipcount;
 
 /* reasons for skipping commands (see comment on breakcmd routine) */
 #define SKIPBREAK	1
diff --git a/bin/sh/trap.c b/bin/sh/trap.c
index a6f929d..834992f 100644
--- a/bin/sh/trap.c
+++ b/bin/sh/trap.c
@@ -412,7 +412,7 @@ void
 dotrap(void)
 {
 	int i;
-	int savestatus;
+	int savestatus, prev_evalskip, prev_skipcount;
 
 	in_dotrap++;
 	for (;;) {
@@ -427,10 +427,36 @@ dotrap(void)
 					 */
 					if (i == SIGCHLD)
 						ignore_sigchld++;
+
+					/*
+					 * Backup current evalskip
+					 * state and reset it before
+					 * executing a trap, so that the
+					 * trap is not disturbed by an
+					 * ongoing break/continue/return
+					 * statement.
+					 */
+					prev_evalskip  = evalskip;
+					prev_skipcount = skipcount;
+					evalskip = 0;
+
 					last_trapsig = i;
 					savestatus = exitstatus;
 					evalstring(trap[i], 0);
 					exitstatus = savestatus;
+
+					/*
+					 * If such a command was not
+					 * already in progress, allow a
+					 * break/continue/return in the
+					 * trap action to have an effect
+					 * outside of it.
+					 */
+					if (prev_evalskip != 0) {
+						evalskip  = prev_evalskip;
+						skipcount = prev_skipcount;
+					}
+
 					if (i == SIGCHLD)
 						ignore_sigchld--;
 				}
@@ -501,6 +527,11 @@ exitshell_savedstatus(void)
 	}
 	handler = &loc1;
 	if ((p = trap[0]) != NULL && *p != '\0') {
+		/*
+		 * Reset evalskip, or the trap on EXIT could be
+		 * interrupted if the last command was a "return".
+		 */
+		evalskip = 0;
 		trap[0] = NULL;
 		evalstring(p, 0);
 	}