From 2d50b7f2ccf6faeaa22d735066d915956f3117a0 Mon Sep 17 00:00:00 2001
From: espie <espie@openbsd.org>
Date: Sun, 21 Dec 2014 09:33:12 +0000
Subject: [PATCH] fix test-redef2: - introduce explicit STORAGE classes for the
 shadow stack entries - delay freeing definitions if they're in-use, keep them
 in a simple array.

okay millert@
---
 usr.bin/m4/look.c | 68 +++++++++++++++++++++++++++++++++++++++++++++--
 usr.bin/m4/main.c |  4 +--
 usr.bin/m4/mdef.h | 21 ++++++++++++---
 usr.bin/m4/misc.c |  4 +--
 4 files changed, 87 insertions(+), 10 deletions(-)

diff --git a/usr.bin/m4/look.c b/usr.bin/m4/look.c
index eeec6569430..ac504570a9f 100644
--- a/usr.bin/m4/look.c
+++ b/usr.bin/m4/look.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: look.c,v 1.23 2014/05/12 19:11:19 espie Exp $	*/
+/*	$OpenBSD: look.c,v 1.24 2014/12/21 09:33:12 espie Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -53,6 +53,9 @@ static void hash_free(void *, void *);
 static void *element_alloc(size_t, void *);
 static void setup_definition(struct macro_definition *, const char *,
     const char *);
+static void free_definition(char *);
+static void keep(char *);
+static int string_in_use(const char *);
 
 static struct ohash_info macro_info = {
 	offsetof(struct ndblock, name),
@@ -152,7 +155,7 @@ macro_define(const char *name, const char *defn)
 	ndptr n = create_entry(name);
 	if (n->d != NULL) {
 		if (n->d->defn != null)
-			free(n->d->defn);
+			free_definition(n->d->defn);
 	} else {
 		n->d = xalloc(sizeof(struct macro_definition), NULL);
 		n->d->next = NULL;
@@ -270,3 +273,64 @@ macro_getbuiltin(const char *name)
 	else
 		return p;
 }
+
+/* XXX things are slightly more complicated than they seem.
+ * a macro may actually be "live" (in the middle of an expansion
+ * on the stack.
+ * So we actually may need to place it in an array for later...
+ */
+
+static int kept_capacity = 0;
+static int kept_size = 0;
+static char **kept = NULL;
+
+static void
+keep(char *ptr)
+{
+	if (kept_capacity <= kept_size) {
+		if (kept_capacity)
+			kept_capacity *= 2;
+		else
+			kept_capacity = 50;
+		kept = xreallocarray(kept, kept_capacity, 
+		    sizeof(char *), "Out of memory while saving %d strings\n", 
+		    kept_capacity);
+	}
+	kept[kept_size++] = ptr;
+}
+
+static int
+string_in_use(const char *ptr) 
+{
+	int i;
+	for (i = 0; i <= sp; i++) {
+		if (sstack[i] == STORAGE_MACRO && mstack[i].sstr == ptr)
+			return 1;
+		}
+	return 0;
+}
+
+
+static void
+free_definition(char *ptr)
+{
+	int i;
+
+	/* first try to free old strings */
+	for (i = 0; i < kept_size; i++) {
+		if (!string_in_use(kept[i])) {
+			kept_size--;
+			free(kept[i]);
+			if (i != kept_size) 
+				kept[i] = kept[kept_size];
+			i--;
+		}
+	}
+
+	/* then deal with us */
+	if (string_in_use(ptr))
+		keep(ptr);
+	else
+		free(ptr);
+}
+
diff --git a/usr.bin/m4/main.c b/usr.bin/m4/main.c
index 1dce48e50e0..b75877fbf9a 100644
--- a/usr.bin/m4/main.c
+++ b/usr.bin/m4/main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: main.c,v 1.83 2014/05/12 19:11:19 espie Exp $	*/
+/*	$OpenBSD: main.c,v 1.84 2014/12/21 09:33:12 espie Exp $	*/
 /*	$NetBSD: main.c,v 1.12 1997/02/08 23:54:49 cgd Exp $	*/
 
 /*-
@@ -397,7 +397,7 @@ macro(void)
 		/*
 		 * now push the string arguments:
 		 */
-				pushs1(macro_getdef(p)->defn);	/* defn string */
+				pushdef(p);			/* defn string */
 				pushs1((char *)macro_name(p));	/* macro name  */
 				pushs(ep);			/* start next..*/
 
diff --git a/usr.bin/m4/mdef.h b/usr.bin/m4/mdef.h
index a4a2bbdc1e6..3185dcb38fa 100644
--- a/usr.bin/m4/mdef.h
+++ b/usr.bin/m4/mdef.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mdef.h,v 1.31 2011/09/27 07:24:02 espie Exp $	*/
+/*	$OpenBSD: mdef.h,v 1.32 2014/12/21 09:33:12 espie Exp $	*/
 /*	$NetBSD: mdef.h,v 1.7 1996/01/13 23:25:27 pk Exp $	*/
 
 /*
@@ -163,6 +163,10 @@ struct input_file {
 	int		c;
 };
 
+#define STORAGE_STRSPACE 0
+#define STORAGE_MACRO 1
+#define STORAGE_OTHER 2
+
 #define CURRENT_NAME	(infile[ilevel].name)
 #define CURRENT_LINE	(infile[ilevel].lineno)
 /*
@@ -178,7 +182,7 @@ struct input_file {
 		if (++sp == STACKMAX)	\
 			enlarge_stack();\
 		mstack[sp].sfra = (x);	\
-		sstack[sp] = 0; \
+		sstack[sp] = STORAGE_OTHER; \
 	} while (0)
 
 #define pushs(x)			\
@@ -186,7 +190,7 @@ struct input_file {
 		if (++sp == STACKMAX)	\
 			enlarge_stack();\
 		mstack[sp].sstr = (x);	\
-		sstack[sp] = 1; \
+		sstack[sp] = STORAGE_STRSPACE; \
 	} while (0)
 
 #define pushs1(x)			\
@@ -194,8 +198,17 @@ struct input_file {
 		if (++sp == STACKMAX)	\
 			enlarge_stack();\
 		mstack[sp].sstr = (x);	\
-		sstack[sp] = 0; \
+		sstack[sp] = STORAGE_OTHER; \
+	} while (0)
+
+#define pushdef(p)			\
+	do {				\
+		if (++sp == STACKMAX)	\
+			enlarge_stack();\
+		mstack[sp].sstr = macro_getdef(p)->defn;\
+		sstack[sp] = STORAGE_MACRO; \
 	} while (0)
+		
 
 /*
  *	    .				   .
diff --git a/usr.bin/m4/misc.c b/usr.bin/m4/misc.c
index 556ecd637b9..122cf0b3dc5 100644
--- a/usr.bin/m4/misc.c
+++ b/usr.bin/m4/misc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: misc.c,v 1.44 2014/05/12 19:11:19 espie Exp $	*/
+/*	$OpenBSD: misc.c,v 1.45 2014/12/21 09:33:12 espie Exp $	*/
 /*	$NetBSD: misc.c,v 1.6 1995/09/28 05:37:41 tls Exp $	*/
 
 /*
@@ -184,7 +184,7 @@ enlarge_strspace()
 		errx(1, "string space overflow");
 	memcpy(newstrspace, strspace, strsize/2);
 	for (i = 0; i <= sp; i++)
-		if (sstack[i])
+		if (sstack[i] == STORAGE_STRSPACE)
 			mstack[i].sstr = (mstack[i].sstr - strspace)
 			    + newstrspace;
 	ep = (ep-strspace) + newstrspace;
-- 
2.20.1