v.gen.c: implement `-d trace_autofree` for conditional tracing comments about autofree

vlib/v/gen/c/cgen.v

@@ -1034,8 +1034,8 @@ fn (mut g Gen) stmts_with_tmp_var(stmts []ast.Stmt, tmp_var string) {
 		stmt := stmts[0]
 		// stmt := stmts[stmts.len-1]
 		if stmt !is ast.FnDecl && g.inside_ternary == 0 {
-			// g.writeln('// autofree scope')
-			// g.writeln('// autofree_scope_vars($stmt.pos.pos) | ${typeof(stmt)}')
+			// g.trace_autofree('// autofree scope')
+			// g.trace_autofree('// autofree_scope_vars($stmt.pos.pos) | ${typeof(stmt)}')
 			// go back 1 position is important so we dont get the
 			// internal scope of for loops and possibly other nodes
 			// g.autofree_scope_vars(stmt.pos.pos - 1)
@@ -1116,7 +1116,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 			} else {
 				// continue or break
 				if g.is_autofree && !g.is_builtin_mod {
-					g.writeln('// free before continue/break')
+					g.trace_autofree('// free before continue/break')
 					g.autofree_scope_vars_stop(node.pos.pos - 1, node.pos.line_nr, true,
 						g.branch_parent_pos)
 				}
@@ -2719,11 +2719,16 @@ fn (mut g Gen) autofree_scope_vars_stop(pos int, line_nr int, free_parent_scopes
 		// TODO why can scope.pos be 0? (only outside fns?)
 		return
 	}
-	g.writeln('// autofree_scope_vars(pos=$pos line_nr=$line_nr scope.pos=$scope.start_pos scope.end_pos=$scope.end_pos)')
+	g.trace_autofree('// autofree_scope_vars(pos=$pos line_nr=$line_nr scope.pos=$scope.start_pos scope.end_pos=$scope.end_pos)')
 	g.autofree_scope_vars2(scope, scope.start_pos, scope.end_pos, line_nr, free_parent_scopes,
 		stop_pos)
 }
 
+[if trace_autofree]
+fn (mut g Gen) trace_autofree(line string) {
+	g.writeln(line)
+}
+
 // fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, end_pos int) {
 fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int, line_nr int, free_parent_scopes bool, stop_pos int) {
 	if isnil(scope) {
@@ -2732,20 +2737,20 @@ fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int
 	for _, obj in scope.objects {
 		match obj {
 			ast.Var {
-				g.writeln('// var "$obj.name" var.pos=$obj.pos.pos var.line_nr=$obj.pos.line_nr')
+				g.trace_autofree('// var "$obj.name" var.pos=$obj.pos.pos var.line_nr=$obj.pos.line_nr')
 				if obj.name == g.returned_var_name {
-					g.writeln('// skipping returned var')
+					g.trace_autofree('// skipping returned var')
 					continue
 				}
 				if obj.is_or {
 					// Skip vars inited with the `or {}`, since they are generated
 					// after the or block in C.
-					g.writeln('// skipping `or{}` var "$obj.name"')
+					g.trace_autofree('// skipping `or{}` var "$obj.name"')
 					continue
 				}
 				if obj.is_tmp {
 					// Skip for loop vars
-					g.writeln('// skipping tmp var "$obj.name"')
+					g.trace_autofree('// skipping tmp var "$obj.name"')
 					continue
 				}
 				// if var.typ == 0 {
@@ -2778,7 +2783,7 @@ fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int
 	// if !isnil(scope.parent) && line_nr > 0 {
 	if free_parent_scopes && !isnil(scope.parent)
 		&& (stop_pos == -1 || scope.parent.start_pos >= stop_pos) {
-		g.writeln('// af parent scope:')
+		g.trace_autofree('// af parent scope:')
 		g.autofree_scope_vars2(scope.parent, start_pos, end_pos, line_nr, true, stop_pos)
 	}
 }
@@ -2801,7 +2806,7 @@ fn (mut g Gen) autofree_variable(v ast.Var) {
 		// Don't free simple string literals.
 		match v.expr {
 			ast.StringLiteral {
-				g.writeln('// str literal')
+				g.trace_autofree('// str literal')
 			}
 			else {
 				// NOTE/TODO: assign_stmt multi returns variables have no expr
@@ -4771,7 +4776,7 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			g.writeln('return ($styp){0};')
 		} else {
 			if g.is_autofree {
-				g.writeln('// free before return (no values returned)')
+				g.trace_autofree('// free before return (no values returned)')
 				g.autofree_scope_vars(node.pos.pos - 1, node.pos.line_nr, true)
 			}
 			g.writeln('return;')

vlib/v/gen/c/comptime.v

@@ -65,7 +65,7 @@ fn (mut g Gen) comptime_call(node ast.ComptimeCall) {
 		}
 		return
 	}
-	g.writeln('// \$method call. sym="$node.sym.name"')
+	g.trace_autofree('// \$method call. sym="$node.sym.name"')
 	if node.method_name == 'method' {
 		// `app.$method()`
 		m := node.sym.find_method(g.comp_for_method) or { return }