Check for double-chaining of types.

Chaining a type twice will form a loop in the type list, causing find_type
to go into an infinite loop.

tools/qfcc/include/type.h

@@ -74,6 +74,7 @@ typedef struct type_s {
 	} t;
 	struct type_s *next;
 	int         freeable;
+	int         allocated;
 	const char *encoding;	///< Objective-QC encoding
 	struct def_s *type_def;	///< offset of qfo encodoing
 } type_t;

tools/qfcc/source/class.c

@@ -336,7 +336,10 @@ get_class (symbol_t *sym, int create)
 	c = calloc (sizeof (class_t), 1);
 	if (sym)
 		c->name = sym->name;
-	new = type_Class;
+	memset (&new, 0, sizeof (new));
+	new.type = ev_invalid;
+	new.name = c->name;
+	new.meta = ty_class;
 	new.t.class = c;
 	c->type = find_type (&new);
 	c->methods = new_methodlist ();

tools/qfcc/source/qfcc.c

@@ -124,10 +124,13 @@ static void
 InitData (void)
 {
 	pr_lineno_t *line;
-	type_t     *type;
+	type_t     *type, *ntype;
 
-	for (type = pr.types; type; type = type->next)
+	for (type = pr.types; type; type = ntype) {
+		ntype = type->next;
+		free_type (type);
 		type->type_def = 0;
+	}
 
 	if (pr.code) {
 		codespace_delete (pr.code);

tools/qfcc/source/type.c

@@ -39,6 +39,7 @@
 #endif
 #include <stdlib.h>
 #include <ctype.h>
+#include <ctype.h>
 
 #include "QF/dstring.h"
 #include "QF/hash.h"
@@ -113,6 +114,8 @@ low_level_type (type_t *type)
 void
 chain_type (type_t *type)
 {
+	if (type->next)
+		internal_error (0, "type already chained");
 	type->next = pr.types;
 	pr.types = type;
 	if (!type->encoding) {
@@ -135,13 +138,18 @@ new_type (void)
 	type_t     *type;
 	ALLOC (1024, type_t, types, type);
 	type->freeable = 1;
+	type->allocated = 1;
 	return type;
 }
 
 void
 free_type (type_t *type)
 {
-	if (!type || !type->freeable)
+	if (!type)
+		return;
+	if (!type->allocated)		// for statically allocated types
+		type->next = 0;
+	if (!type->freeable)
 		return;
 	switch (type->type) {
 		case ev_void: