ash: eval: Return status in eval functions

Backported from dash:

    eval: Return status in eval functions

    The exit status is currently clobbered too early for case statements
    and loops.  This patch fixes it by making the eval functions return
    the current exit status and setting them in one place -- evaltree.

    Harald van Dijk pointed out a number of bugs in the original patch.

function                                             old     new   delta
evalcommand                                         1226    1242     +16
cmdloop                                              383     398     +15
evalfor                                              223     227      +4
evalcase                                             271     275      +4
localcmd                                             348     350      +2
evaltreenr                                           927     928      +1
evaltree                                             927     928      +1
evalsubshell                                         150     151      +1
evalpipe                                             356     357      +1
parse_command                                       1585    1584      -1
evalloop                                             177     164     -13
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 9/2 up/down: 45/-14)             Total: 31 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 81 insertions, 55 deletions

diff --git a/shell/ash.c b/shell/ash.c
index a113ff1..ec006af 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -5864,7 +5864,7 @@ struct backcmd {                /* result of evalbackcmd */
 /* These forward decls are needed to use "eval" code for backticks handling: */
 static uint8_t back_exitstatus; /* exit status of backquoted command */
 #define EV_EXIT 01              /* exit after evaluating tree */
-static void evaltree(union node *, int);
+static int evaltree(union node *, int);
 
 static void FAST_FUNC
 evalbackcmd(union node *n, struct backcmd *result)
@@ -8412,13 +8412,13 @@ dotrap(void)
 }
 
 /* forward declarations - evaluation is fairly recursive business... */
-static void evalloop(union node *, int);
-static void evalfor(union node *, int);
-static void evalcase(union node *, int);
-static void evalsubshell(union node *, int);
+static int evalloop(union node *, int);
+static int evalfor(union node *, int);
+static int evalcase(union node *, int);
+static int evalsubshell(union node *, int);
 static void expredir(union node *);
-static void evalpipe(union node *, int);
-static void evalcommand(union node *, int);
+static int evalpipe(union node *, int);
+static int evalcommand(union node *, int);
 static int evalbltin(const struct builtincmd *, int, char **);
 static void prehash(union node *);
 
@@ -8426,14 +8426,14 @@ static void prehash(union node *);
  * Evaluate a parse tree.  The value is left in the global variable
  * exitstatus.
  */
-static void
+static int
 evaltree(union node *n, int flags)
 {
 	struct jmploc *volatile savehandler = exception_handler;
 	struct jmploc jmploc;
 	int checkexit = 0;
-	void (*evalfn)(union node *, int);
-	int status;
+	int (*evalfn)(union node *, int);
+	int status = 0;
 	int int_level;
 
 	SAVE_INT(int_level);
@@ -8470,15 +8470,13 @@ evaltree(union node *n, int flags)
 		break;
 #endif
 	case NNOT:
-		evaltree(n->nnot.com, EV_TESTED);
-		status = !exitstatus;
+		status = !evaltree(n->nnot.com, EV_TESTED);
 		goto setstatus;
 	case NREDIR:
 		expredir(n->nredir.redirect);
 		status = redirectsafe(n->nredir.redirect, REDIR_PUSH);
 		if (!status) {
-			evaltree(n->nredir.n, flags & EV_TESTED);
-			status = exitstatus;
+			status = evaltree(n->nredir.n, flags & EV_TESTED);
 		}
 		popredir(/*drop:*/ 0, /*restore:*/ 0 /* not sure */);
 		goto setstatus;
@@ -8518,27 +8516,24 @@ evaltree(union node *n, int flags)
 #error NOR + 1 != NSEMI
 #endif
 		unsigned is_or = n->type - NAND;
-		evaltree(
+		status = evaltree(
 			n->nbinary.ch1,
 			(flags | ((is_or >> 1) - 1)) & EV_TESTED
 		);
-		if ((!exitstatus) == is_or)
+		if (!status == is_or || evalskip)
 			break;
-		if (!evalskip) {
-			n = n->nbinary.ch2;
+		n = n->nbinary.ch2;
  evaln:
-			evalfn = evaltree;
+		evalfn = evaltree;
  calleval:
-			evalfn(n, flags);
-			break;
-		}
-		break;
+		status = evalfn(n, flags);
+		goto setstatus;
 	}
 	case NIF:
-		evaltree(n->nif.test, EV_TESTED);
+		status = evaltree(n->nif.test, EV_TESTED);
 		if (evalskip)
 			break;
-		if (exitstatus == 0) {
+		if (!status) {
 			n = n->nif.ifpart;
 			goto evaln;
 		}
@@ -8546,11 +8541,14 @@ evaltree(union node *n, int flags)
 			n = n->nif.elsepart;
 			goto evaln;
 		}
-		goto success;
+		status = 0;
+		goto setstatus;
 	case NDEFUN:
 		defun(n->narg.text, n->narg.next);
- success:
-		status = 0;
+		/* Not necessary. To test it:
+		 * "false; f() { qwerty; }; echo $?" should print 0.
+		 */
+		/* status = 0; */
  setstatus:
 		exitstatus = status;
 		break;
@@ -8565,7 +8563,7 @@ evaltree(union node *n, int flags)
 	 */
 	if (pending_sig && dotrap())
 		goto exexit;
-	if (checkexit & exitstatus)
+	if (checkexit & status)
 		evalskip |= SKIPEVAL;
 
 	if (flags & EV_EXIT) {
@@ -8575,14 +8573,16 @@ evaltree(union node *n, int flags)
 
 	RESTORE_INT(int_level);
 	TRACE(("leaving evaltree (no interrupts)\n"));
+
+	return exitstatus;
 }
 
 #if !defined(__alpha__) || (defined(__GNUC__) && __GNUC__ >= 3)
 static
 #endif
-void evaltreenr(union node *, int) __attribute__ ((alias("evaltree"),__noreturn__));
+int evaltreenr(union node *, int) __attribute__ ((alias("evaltree"),__noreturn__));
 
-static void
+static int
 evalloop(union node *n, int flags)
 {
 	int status;
@@ -8593,7 +8593,7 @@ evalloop(union node *n, int flags)
 	for (;;) {
 		int i;
 
-		evaltree(n->nbinary.ch1, EV_TESTED);
+		i = evaltree(n->nbinary.ch1, EV_TESTED);
 		if (evalskip) {
  skipping:
 			if (evalskip == SKIPCONT && --skipcount <= 0) {
@@ -8604,27 +8604,28 @@ evalloop(union node *n, int flags)
 				evalskip = 0;
 			break;
 		}
-		i = exitstatus;
 		if (n->type != NWHILE)
 			i = !i;
 		if (i != 0)
 			break;
-		evaltree(n->nbinary.ch2, flags);
-		status = exitstatus;
+		status = evaltree(n->nbinary.ch2, flags);
 		if (evalskip)
 			goto skipping;
 	}
-	loopnest--;
 	exitstatus = status;
+	loopnest--;
+
+	return status;
 }
 
-static void
+static int
 evalfor(union node *n, int flags)
 {
 	struct arglist arglist;
 	union node *argp;
 	struct strlist *sp;
 	struct stackmark smark;
+	int status = 0;
 
 	setstackmark(&smark);
 	arglist.list = NULL;
@@ -8637,12 +8638,11 @@ evalfor(union node *n, int flags)
 	}
 	*arglist.lastp = NULL;
 
-	exitstatus = 0;
 	loopnest++;
 	flags &= EV_TESTED;
 	for (sp = arglist.list; sp; sp = sp->next) {
 		setvar0(n->nfor.var, sp->text);
-		evaltree(n->nfor.body, flags);
+		status = evaltree(n->nfor.body, flags);
 		if (evalskip) {
 			if (evalskip == SKIPCONT && --skipcount <= 0) {
 				evalskip = 0;
@@ -8656,26 +8656,32 @@ evalfor(union node *n, int flags)
 	loopnest--;
  out:
 	popstackmark(&smark);
+
+	return status;
 }
 
-static void
+static int
 evalcase(union node *n, int flags)
 {
 	union node *cp;
 	union node *patp;
 	struct arglist arglist;
 	struct stackmark smark;
+	int status = 0;
 
 	setstackmark(&smark);
 	arglist.list = NULL;
 	arglist.lastp = &arglist.list;
 	expandarg(n->ncase.expr, &arglist, EXP_TILDE);
-	exitstatus = 0;
 	for (cp = n->ncase.cases; cp && evalskip == 0; cp = cp->nclist.next) {
 		for (patp = cp->nclist.pattern; patp; patp = patp->narg.next) {
 			if (casematch(patp, arglist.list->text)) {
-				if (evalskip == 0) {
-					evaltree(cp->nclist.body, flags);
+				/* Ensure body is non-empty as otherwise
+				 * EV_EXIT may prevent us from setting the
+				 * exit status.
+				 */
+				if (evalskip == 0 && cp->nclist.body) {
+					status = evaltree(cp->nclist.body, flags);
 				}
 				goto out;
 			}
@@ -8683,12 +8689,14 @@ evalcase(union node *n, int flags)
 	}
  out:
 	popstackmark(&smark);
+
+	return status;
 }
 
 /*
  * Kick off a subshell to evaluate a tree.
  */
-static void
+static int
 evalsubshell(union node *n, int flags)
 {
 	struct job *jp;
@@ -8714,8 +8722,8 @@ evalsubshell(union node *n, int flags)
 	status = 0;
 	if (!backgnd)
 		status = waitforjob(jp);
-	exitstatus = status;
 	INT_ON;
+	return status;
 }
 
 /*
@@ -8788,7 +8796,7 @@ expredir(union node *n)
  * of the shell, which make the last process in a pipeline the parent
  * of all the rest.)
  */
-static void
+static int
 evalpipe(union node *n, int flags)
 {
 	struct job *jp;
@@ -8796,6 +8804,7 @@ evalpipe(union node *n, int flags)
 	int pipelen;
 	int prevfd;
 	int pip[2];
+	int status = 0;
 
 	TRACE(("evalpipe(0x%lx) called\n", (long)n));
 	pipelen = 0;
@@ -8838,10 +8847,12 @@ evalpipe(union node *n, int flags)
 			close(pip[1]);
 	}
 	if (n->npipe.pipe_backgnd == 0) {
-		exitstatus = waitforjob(jp);
-		TRACE(("evalpipe:  job done exit status %d\n", exitstatus));
+		status = waitforjob(jp);
+		TRACE(("evalpipe:  job done exit status %d\n", status));
 	}
 	INT_ON;
+
+	return status;
 }
 
 /*
@@ -9328,7 +9339,7 @@ bltincmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 	 * as POSIX mandates */
 	return back_exitstatus;
 }
-static void
+static int
 evalcommand(union node *cmd, int flags)
 {
 	static const struct builtincmd null_bltin = {
@@ -9511,9 +9522,9 @@ evalcommand(union node *cmd, int flags)
 			jp = makejob(/*cmd,*/ 1);
 			if (forkshell(jp, cmd, FORK_FG) != 0) {
 				/* parent */
-				exitstatus = waitforjob(jp);
+				status = waitforjob(jp);
 				INT_ON;
-				TRACE(("forked child exited with %d\n", exitstatus));
+				TRACE(("forked child exited with %d\n", status));
 				break;
 			}
 			/* child */
@@ -9559,7 +9570,7 @@ evalcommand(union node *cmd, int flags)
 			}
 			FORCE_INT_ON;
 		}
-		break;
+		goto readstatus;
 
 	case CMDFUNCTION:
 		listsetvar(varlist.list, 0);
@@ -9567,6 +9578,8 @@ evalcommand(union node *cmd, int flags)
 		dowait(DOWAIT_NONBLOCK, NULL);
 		if (evalfun(cmdentry.u.func, argc, argv, flags))
 			goto raise;
+ readstatus:
+		status = exitstatus;
 		break;
 	} /* switch */
 
@@ -9580,6 +9593,8 @@ evalcommand(union node *cmd, int flags)
 		setvar0("_", lastarg);
 	}
 	popstackmark(&smark);
+
+	return status;
 }
 
 static int
@@ -12205,13 +12220,18 @@ evalstring(char *s, int mask)
 	union node *n;
 	struct stackmark smark;
 	int skip;
+//	int status;
 
 	setinputstring(s);
 	setstackmark(&smark);
 
 	skip = 0;
 	while ((n = parsecmd(0)) != NODE_EOF) {
-		evaltree(n, 0);
+		int i;
+
+		i = evaltree(n, 0);
+//		if (n)
+//			status = i;
 		popstackmark(&smark);
 		skip = evalskip;
 		if (skip)
@@ -12222,6 +12242,7 @@ evalstring(char *s, int mask)
 	skip &= mask;
 	evalskip = skip;
 	return skip;
+//	return status;
 }
 
 /*
@@ -12264,6 +12285,7 @@ cmdloop(int top)
 	union node *n;
 	struct stackmark smark;
 	int inter;
+	int status = 0;
 	int numeof = 0;
 
 	TRACE(("cmdloop(%d) called\n", top));
@@ -12295,10 +12317,14 @@ cmdloop(int top)
 			}
 			numeof++;
 		} else if (nflag == 0) {
+			int i;
+
 			/* job_warning can only be 2,1,0. Here 2->1, 1/0->0 */
 			job_warning >>= 1;
 			numeof = 0;
-			evaltree(n, 0);
+			i = evaltree(n, 0);
+			if (n)
+				status = i;
 		}
 		popstackmark(&smark);
 		skip = evalskip;
@@ -12308,7 +12334,7 @@ cmdloop(int top)
 			return skip & SKIPEVAL;
 		}
 	}
-	return 0;
+	return status;
 }
 
 /*