sh: Solve the alias recursion problem in a less hackish way.

Add the space to avoid alias recursion when the alias is expanded, not when
it is added.

As a result, displaying an alias via command -v, command -V or type no
longer erroneously appends a space. Adjust the tests so they now require
this bug to be absent.

bin/sh/alias.c

@@ -68,18 +68,7 @@ setalias(const char *name, const char *val)
 		if (equal(name, ap->name)) {
 			INTOFF;
 			ckfree(ap->val);
-			/* See HACK below. */
-#ifdef notyet
 			ap->val	= savestr(val);
-#else
-			{
-			size_t len = strlen(val);
-			ap->val = ckmalloc(len + 2);
-			memcpy(ap->val, val, len);
-			ap->val[len] = ' ';
-			ap->val[len+1] = '\0';
-			}
-#endif
 			INTON;
 			return;
 		}
@@ -88,34 +77,7 @@ setalias(const char *name, const char *val)
 	INTOFF;
 	ap = ckmalloc(sizeof (struct alias));
 	ap->name = savestr(name);
-	/*
-	 * XXX - HACK: in order that the parser will not finish reading the
-	 * alias value off the input before processing the next alias, we
-	 * dummy up an extra space at the end of the alias.  This is a crock
-	 * and should be re-thought.  The idea (if you feel inclined to help)
-	 * is to avoid alias recursions.  The mechanism used is: when
-	 * expanding an alias, the value of the alias is pushed back on the
-	 * input as a string and a pointer to the alias is stored with the
-	 * string.  The alias is marked as being in use.  When the input
-	 * routine finishes reading the string, it marks the alias not
-	 * in use.  The problem is synchronization with the parser.  Since
-	 * it reads ahead, the alias is marked not in use before the
-	 * resulting token(s) is next checked for further alias sub.  The
-	 * H A C K is that we add a little fluff after the alias value
-	 * so that the string will not be exhausted.  This is a good
-	 * idea ------- ***NOT***
-	 */
-#ifdef notyet
 	ap->val = savestr(val);
-#else /* hack */
-	{
-	size_t len = strlen(val);
-	ap->val = ckmalloc(len + 2);
-	memcpy(ap->val, val, len);
-	ap->val[len] = ' ';	/* fluff */
-	ap->val[len+1] = '\0';
-	}
-#endif
 	ap->flag = 0;
 	ap->next = *app;
 	*app = ap;
@@ -207,14 +169,8 @@ comparealiases(const void *p1, const void *p2)
 static void
 printalias(const struct alias *a)
 {
-	char *p;
-
 	out1fmt("%s=", a->name);
-	/* Don't print the space added above. */
-	p = a->val + strlen(a->val) - 1;
-	*p = '\0';
 	out1qstr(a->val);
-	*p = ' ';
 	out1c('\n');
 }
 

bin/sh/input.c

@@ -226,7 +226,14 @@ preadbuffer(void)
 	int more;
 	char savec;
 
-	if (parsefile->strpush) {
+	while (parsefile->strpush) {
+		/*
+		 * Add a space to the end of an alias to ensure that the
+		 * alias remains in use while parsing its last word.
+		 * This avoids alias recursions.
+		 */
+		if (parsenleft == -1 && parsefile->strpush->ap != NULL)
+			return ' ';
 		popstring();
 		if (--parsenleft >= 0)
 			return (*parsenextc++);

bin/sh/tests/builtins/command3.0.stdout

@@ -4,4 +4,4 @@ true
 fun
 break
 if
-alias foo='bar '
+alias foo=bar

bin/sh/tests/builtins/command5.0.stdout

@@ -5,4 +5,4 @@ fun is a shell function
 break is a special shell builtin
 if is a shell keyword
 { is a shell keyword
-foo is an alias for bar 
+foo is an alias for bar

bin/sh/tests/builtins/command6.0.stdout

@@ -4,4 +4,4 @@ fun is a shell function
 break is a special shell builtin
 if is a shell keyword
 { is a shell keyword
-foo is an alias for bar 
+foo is an alias for bar