From a256b373624d3c6c6f38bce03b58cc38fab7e1e2 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 28 Apr 2020 01:15:26 +1000
Subject: parser: Fix handling of empty aliases

Dash was incorrectly handling empty aliases. When attempting to use an
empty alias with nothing else, I'm (incorrectly) prompted for more
input:

```
$ alias empty=''
$ empty
>
```

Other shells (e.g., bash, yash) correctly handle the lone, empty alias as an
empty command:

```
$ alias empty=''
$ empty
$
```

The problem here is that we incorrectly enter the loop eating TNLs
in readtoken().  This patch fixes it by setting checkkwd correctly.

Reported-by: Michael Greenberg <michael.greenberg@pomona.edu>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 src/parser.c | 29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/src/parser.c b/src/parser.c
index b318b08..5c9e9a0 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -115,7 +115,6 @@ STATIC union node *simplecmd(void);
 STATIC union node *makename(void);
 STATIC void parsefname(void);
 STATIC void parseheredoc(void);
-STATIC int peektoken(void);
 STATIC int readtoken(void);
 STATIC int xxreadtoken(void);
 STATIC int pgetc_eatbnl();
@@ -161,21 +160,23 @@ parsecmd(int interact)
 STATIC union node *
 list(int nlflag)
 {
+	int chknl = nlflag & 1 ? 0 : CHKNL;
 	union node *n1, *n2, *n3;
 	int tok;
 
 	n1 = NULL;
 	for (;;) {
-		switch (readtoken()) {
+		checkkwd = chknl | CHKKWD | CHKALIAS;
+		tok = readtoken();
+		switch (tok) {
 		case TNL:
-			if (!(nlflag & 1))
-				break;
 			parseheredoc();
 			return n1;
 
 		case TEOF:
-			if (!n1 && (nlflag & 1))
+			if (!n1 && !chknl)
 				n1 = NEOF;
+out_eof:
 			parseheredoc();
 			tokpushback++;
 			lasttoken = TEOF;
@@ -183,8 +184,7 @@ list(int nlflag)
 		}
 
 		tokpushback++;
-		checkkwd = CHKNL | CHKKWD | CHKALIAS;
-		if (nlflag == 2 && tokendlist[peektoken()])
+		if (nlflag == 2 && tokendlist[tok])
 			return n1;
 		nlflag |= 2;
 
@@ -214,15 +214,16 @@ list(int nlflag)
 			n1 = n3;
 		}
 		switch (tok) {
-		case TNL:
 		case TEOF:
+			goto out_eof;
+		case TNL:
 			tokpushback++;
 			/* fall through */
 		case TBACKGND:
 		case TSEMI:
 			break;
 		default:
-			if ((nlflag & 1))
+			if (!chknl)
 				synexpect(-1);
 			tokpushback++;
 			return n1;
@@ -685,16 +686,6 @@ parseheredoc(void)
 	}
 }
 
-STATIC int
-peektoken(void)
-{
-	int t;
-
-	t = readtoken();
-	tokpushback++;
-	return (t);
-}
-
 STATIC int
 readtoken(void)
 {
-- 
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