cgen: fix autofree used vars on return (fix #25196) (#25198)

vlib/v/gen/c/autofree.v

@@ -62,7 +62,7 @@ fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int
 		match obj {
 			ast.Var {
 				g.trace_autofree('// var "${obj.name}" var.pos=${obj.pos.pos} var.line_nr=${obj.pos.line_nr}')
-				if obj.name == g.returned_var_name {
+				if obj.name in g.returned_var_names {
 					g.print_autofree_var(obj, 'returned from function')
 					g.trace_autofree('// skipping returned var')
 					continue
@@ -247,3 +247,17 @@ fn (mut g Gen) autofree_var_call(free_fn_name string, v ast.Var) {
 	}
 	g.autofree_scope_stmts << af.str()
 }
+
+fn (mut g Gen) detect_used_var_on_return(expr ast.Expr) {
+	match expr {
+		ast.Ident {
+			g.returned_var_names[expr.name] = true
+		}
+		ast.StructInit {
+			for field_expr in expr.init_fields {
+				g.detect_used_var_on_return(field_expr.expr)
+			}
+		}
+		else {}
+	}
+}

vlib/v/gen/c/cgen.v

@@ -231,11 +231,11 @@ mut:
 	// where an aggregate (at least two types) is generated
 	// sum type deref needs to know which index to deref because unions take care of the correct field
 	aggregate_type_idx  int
-	arg_no_auto_deref   bool     // smartcast must not be dereferenced
-	branch_parent_pos   int      // used in BranchStmt (continue/break) for autofree stop position
-	returned_var_name   string   // to detect that a var doesn't need to be freed since it's being returned
-	infix_left_var_name string   // a && if expr
-	curr_var_name       []string // curr var name on assignment
+	arg_no_auto_deref   bool            // smartcast must not be dereferenced
+	branch_parent_pos   int             // used in BranchStmt (continue/break) for autofree stop position
+	returned_var_names  map[string]bool // to detect that vars doesn't need to be freed since it's being returned
+	infix_left_var_name string          // a && if expr
+	curr_var_name       []string        // curr var name on assignment
 	called_fn_name      string
 	timers              &util.Timers = util.get_timers()
 	force_main_console  bool              // true when @[console] used on fn main()
@@ -6241,6 +6241,9 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				g.writeln(' }, (${option_name}*)(&${tmpvar}), sizeof(${styp}));')
 			}
 			g.write_defer_stmts_when_needed()
+			if g.is_autofree {
+				g.detect_used_var_on_return(expr0)
+			}
 			g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
 			g.writeln('return ${tmpvar};')
 			return
@@ -6286,6 +6289,9 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 				g.writeln(' }, (${result_name}*)(&${tmpvar}), sizeof(${styp}));')
 			}
 			g.write_defer_stmts_when_needed()
+			if g.is_autofree {
+				g.detect_used_var_on_return(expr0)
+			}
 			g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
 			g.writeln('return ${tmpvar};')
 			return
@@ -6294,9 +6300,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 		// set free_parent_scopes to true, since all variables defined in parent
 		// scopes need to be freed before the return
 		if g.is_autofree {
-			if expr0 is ast.Ident {
-				g.returned_var_name = expr0.name
-			}
+			g.detect_used_var_on_return(expr0)
 			if !use_tmp_var && !g.is_builtin_mod {
 				use_tmp_var = expr0 is ast.CallExpr
 			}

vlib/v/gen/c/fn.v

@@ -196,7 +196,7 @@ fn (mut g Gen) gen_fn_decl(node &ast.FnDecl, skip bool) {
 	}
 	*/
 
-	g.returned_var_name = ''
+	g.returned_var_names.clear()
 	old_g_autofree := g.is_autofree
 	if node.is_manualfree {
 		g.is_autofree = false

vlib/v/gen/c/testdata/autofree_toml.c.must_have

@@ -0,0 +1,9 @@
+_result_toml__scanner__Scanner_ptr toml__scanner__new_scanner(toml__scanner__Config config) {
+	_result_toml__scanner__Scanner_ptr _t3 = {0};
+	_result_ok(&(toml__scanner__Scanner*[]) { s }, (_result*)(&_t3), sizeof(toml__scanner__Scanner*));
+	return _t3;
+}
+toml__ast__Quoted toml__parser__Parser_quoted(toml__parser__Parser* p) {
+	return ((toml__ast__Quoted){.text =  string_clone_static(lit),.pos = toml__token__Token_pos(&p->tok),.is_multiline = is_multiline,.quote = quote,});
+}
+

vlib/v/gen/c/testdata/autofree_toml.vv

@@ -0,0 +1,15 @@
+// vtest vflags: -autofree
+import toml
+import os
+
+fn main() {
+	config_fname := 'config.toml'
+	tab_title := 'test tab title'
+	if !os.exists(config_fname) {
+		mut f := os.create(config_fname) or { panic(err) }
+		f.writeln('tab_title = "${tab_title}"') or { panic(err) }
+		f.close()
+	}
+	doc := toml.parse_file(config_fname) or { panic(err) }
+	assert doc.value('tab_title').string() == tab_title
+}

vlib/v/slow_tests/valgrind/1.strings_and_arrays.v

@@ -398,6 +398,7 @@ fn advanced_options() {
 	s2 := parse_header1('foo:bar') or { return }
 	_ := s.len + s2.len // avoid warning for unused variables
 	// TODO: fix -autofree, so that it adds this free automatically:
+	unsafe { s.free() }
 	unsafe { s2.free() }
 }