[qfcc] Clean up the last general uses of expr's next

It's now meant only for ALLOC. Interestingly, when DEBUG_QF_MEMORY is
defined in expr.c, something breaks badly with vkgen (no sniffles out of
valgrind, though), but everything is fine with it not defined. It seems
there may be some unpleasant UB going on somewhere.

tools/qfcc/include/expr.h

@@ -129,7 +129,7 @@ typedef struct {
 
 typedef struct {
 	type_t     *type;			///< Type of vector (vector/quaternion)
-	const expr_t *list;			///< Linked list of element expressions.
+	ex_list_t   list;			///< Linked list of element expressions.
 } ex_vector_t;
 
 typedef struct {
@@ -310,7 +310,7 @@ typedef struct {
 #define POINTER_VAL(p) (((p).def ? (p).def->offset : 0) + (p).val)
 
 typedef struct expr_s {
-	expr_t *next;
+	expr_t     *next;
 	expr_type   type;			///< the type of the result of this expression
 	int         line;			///< source line that generated this expression
 	pr_string_t file;			///< source file that generated this expression

tools/qfcc/source/dot_expr.c

@@ -178,8 +178,6 @@ print_bool (dstring_t *dstr, const expr_t *e, int level, int id, const expr_t *n
 				   i);
 	dasprintf (dstr, "%*s</table>\n", indent + 2, "");
 	dasprintf (dstr, "%*s>];\n", indent, "");
-	if (e->next)
-		next = e->next;
 	_print_expr (dstr, e->boolean.e, level, id, next);
 	for (i = 0; i < tl_count; i++)
 		dasprintf (dstr, "%*se_%p:t%d -> e_%p;\n", indent, "", e, i,
@@ -195,8 +193,6 @@ print_label (dstring_t *dstr, const expr_t *e, int level, int id, const expr_t *
 {
 	int         indent = level * 2 + 2;
 
-	if (e->next)
-		next = e->next;
 	if (next)
 		dasprintf (dstr, "%*se_%p -> e_%p [constraint=true,style=dashed];\n",
 				   indent, "", e, next);
@@ -209,8 +205,6 @@ print_labelref (dstring_t *dstr, const expr_t *e, int level, int id, const expr_
 {
 	int         indent = level * 2 + 2;
 
-	if (e->next)
-		next = e->next;
 	if (next)
 		dasprintf (dstr, "%*se_%p -> e_%p [constraint=true,style=dashed];\n",
 				   indent, "", e, next);
@@ -227,7 +221,7 @@ print_block (dstring_t *dstr, const expr_t *e, int level, int id,
 	const expr_t *exprs[num_exprs + 1];
 
 	list_scatter (&e->block.list, exprs);
-	exprs[num_exprs] = 0;
+	exprs[num_exprs] = next;
 
 	int colspan = num_exprs ? num_exprs : 1;
 
@@ -397,9 +391,6 @@ print_conditional (dstring_t *dstr, const expr_t *e, int level, int id, const ex
 			   e->branch.test);
 	dasprintf (dstr, "%*se_%p -> \"e_%p\" [label=\"g\"];\n", indent, "", e,
 			   e->branch.target);
-	if (e->next) {
-		next = e->next;
-	}
 	if (next) {
 		dasprintf (dstr, "%*se_%p -> e_%p [constraint=true,"
 				   "style=dashed];\n", indent, "", e, next);
@@ -520,7 +511,8 @@ print_vector (dstring_t *dstr, const expr_t *e, int level, int id, const expr_t
 {
 	int         indent = level * 2 + 2;
 
-	for (const expr_t *ele = e->vector.list; ele; ele = ele->next) {
+	for (auto li = e->vector.list.head; li; li = li->next) {
+		auto ele = li->expr;
 		_print_expr (dstr, ele, level, id, next);
 		dasprintf (dstr, "%*se_%p -> \"e_%p\";\n", indent, "", e, ele);
 	}

tools/qfcc/source/expr.c

@@ -1384,9 +1384,6 @@ append_expr (expr_t *block, const expr_t *e)
 	if (!e || e->type == ex_error)
 		return block;
 
-	if (e->next)
-		internal_error (e, "append_expr: expr loop detected");
-
 	auto li = new_listitem (e);
 	*block->block.tail = li;
 	block->block.tail = &li->next;
@@ -1403,9 +1400,6 @@ prepend_expr (expr_t *block, const expr_t *e)
 	if (!e || e->type == ex_error)
 		return block;
 
-	if (e->next)
-		internal_error (e, "append_expr: expr loop detected");
-
 	auto li = new_listitem (e);
 	li->next = block->block.head;
 	block->block.head = li;
@@ -1591,7 +1585,6 @@ convert_from_bool (const expr_t *e, type_t *type)
 	}
 	auto cond = new_expr ();
 	*cond = *e;
-	cond->next = 0;
 
 	return conditional_expr (cond, one, zero);
 }

tools/qfcc/source/expr_assign.c

@@ -230,12 +230,15 @@ copy_qv_elements (expr_t *block, const expr_t *dst, const expr_t *src)
 	const expr_t *dw, *sw;
 	const expr_t *ds, *ss;
 	const expr_t *dv, *sv;
+	int         count = list_count (&src->vector.list);
+	const expr_t *components[count];
+	list_scatter (&src->vector.list, components);
 
 	if (is_vector (src->vector.type)) {
 		// guaranteed to have three elements
-		sx = src->vector.list;
-		sy = sx->next;
-		sz = sy->next;
+		sx = components[0];
+		sy = components[1];
+		sz = components[2];
 		dx = field_expr (dst, new_name_expr ("x"));
 		dy = field_expr (dst, new_name_expr ("y"));
 		dz = field_expr (dst, new_name_expr ("z"));
@@ -244,12 +247,12 @@ copy_qv_elements (expr_t *block, const expr_t *dst, const expr_t *src)
 		append_expr (block, assign_expr (dz, sz));
 	} else {
 		// guaranteed to have two or four elements
-		if (src->vector.list->next->next) {
+		if (count == 4) {
 			// four vals: x, y, z, w
-			sx = src->vector.list;
-			sy = sx->next;
-			sz = sy->next;
-			sw = sz->next;
+			sx = components[0];
+			sy = components[1];
+			sz = components[2];
+			sw = components[3];
 			dx = field_expr (dst, new_name_expr ("x"));
 			dy = field_expr (dst, new_name_expr ("y"));
 			dz = field_expr (dst, new_name_expr ("z"));
@@ -260,8 +263,8 @@ copy_qv_elements (expr_t *block, const expr_t *dst, const expr_t *src)
 			append_expr (block, assign_expr (dw, sw));
 		} else {
 			// v, s
-			sv = src->vector.list;
-			ss = sv->next;
+			sv = components[0];
+			ss = components[1];
 			dv = field_expr (dst, new_name_expr ("v"));
 			ds = field_expr (dst, new_name_expr ("s"));
 			append_expr (block, assign_expr (dv, sv));
@@ -274,7 +277,8 @@ static int
 copy_elements (expr_t *block, const expr_t *dst, const expr_t *src, int base)
 {
 	int         index = 0;
-	for (const expr_t *e = src->vector.list; e; e = e->next) {
+	for (auto li = src->vector.list.head; li; li = li->next) {
+		auto e = li->expr;
 		if (e->type == ex_vector) {
 			index += copy_elements (block, dst, e, index + base);
 		} else {

tools/qfcc/source/expr_vector.c

@@ -132,14 +132,9 @@ new_vector_list (const expr_t *expr_list)
 		return vec;
 	}
 
-	for (int i = 0; i < count; i++) {
-		//FIXME this should use ex_list
-		((expr_t *) elements[i])->next = (expr_t *) elements[i + 1];
-	}
-
 	expr_t     *vec = new_expr ();
 	vec->type = ex_vector;
 	vec->vector.type = vector_type (ele_type, width);
-	vec->vector.list = elements[0];
+	list_gather (&vec->vector.list, elements, count);
 	return vec;
 }

tools/qfcc/source/statements.c

@@ -1926,7 +1926,8 @@ static int
 statement_copy_elements (sblock_t **sblock, const expr_t *dst, const expr_t *src, int base)
 {
 	int         index = 0;
-	for (const expr_t *e = src->vector.list; e; e = e->next) {
+	for (auto li = src->vector.list.head; li; li = li->next) {
+		auto e = li->expr;
 		if (e->type == ex_vector) {
 			index += statement_copy_elements (sblock, dst, e, index + base);
 		} else {
@@ -2073,15 +2074,12 @@ build_bool_block (expr_t *block, expr_t *e)
 			build_bool_block (block, (expr_t *) e->boolean.e);
 			return;
 		case ex_label:
-			e->next = 0;
 			append_expr (block, e);
 			return;
 		case ex_assign:
-			e->next = 0;
 			append_expr (block, e);
 			return;
 		case ex_branch:
-			e->next = 0;
 			append_expr (block, e);
 			return;
 		case ex_expr:
@@ -2089,7 +2087,6 @@ build_bool_block (expr_t *block, expr_t *e)
 				build_bool_block (block, (expr_t *) e->expr.e1);
 				build_bool_block (block, (expr_t *) e->expr.e2);
 			} else {
-				e->next = 0;
 				append_expr (block, e);
 			}
 			return;