cgen: fix autofree inserting string declarations for multiple functions calls (#18723)

vlib/v/gen/c/cgen.v

@@ -3121,7 +3121,12 @@ fn (mut g Gen) expr(node_ ast.Expr) {
 					g.writeln('(${shared_styp}*)__dup${shared_styp}(&(${shared_styp}){.mtx = {0}, .val =')
 				}
 			}
-			last_stmt_pos := if g.stmt_path_pos.len > 0 { g.stmt_path_pos.last() } else { 0 }
+			stmt_before_call_expr_pos := if g.stmt_path_pos.len > 0 {
+				g.stmt_path_pos.last()
+			} else {
+				0
+			}
+
 			g.call_expr(node)
 			if g.is_autofree && !g.is_builtin_mod && !g.is_js_call && g.strs_to_free0.len == 0
 				&& !g.inside_lambda {
@@ -3130,7 +3135,8 @@ fn (mut g Gen) expr(node_ ast.Expr) {
 				// so just skip it
 				g.autofree_call_pregen(node)
 				if g.strs_to_free0.len > 0 {
-					g.insert_at(last_stmt_pos, g.strs_to_free0.join('\n') + '/* inserted before */')
+					g.insert_at(stmt_before_call_expr_pos, g.strs_to_free0.join('\n') +
+						'/* inserted before */')
 				}
 				g.strs_to_free0 = []
 			}

vlib/v/gen/c/fn.v

@@ -2021,7 +2021,7 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 					fn_name := node.name.replace('.', '_')
 					// name := '_tt${g.tmp_count_af}_arg_expr_${fn_name}_$i'
 					name := '_arg_expr_${fn_name}_${i + 1}_${node.pos.pos}'
-					g.write('/*af arg*/' + name)
+					g.write('/*autofree arg*/' + name)
 				}
 			} else {
 				g.ref_or_deref_arg(arg, expected_types[i], node.language)

vlib/v/gen/c/text_manipulation.v

@@ -84,4 +84,14 @@ fn (mut g Gen) insert_at(pos int, s string) {
 	// g.out_parallel[g.out_idx].cut_to(pos)
 	g.writeln(s)
 	g.write(cur_line)
+
+	// After modifying the code in the buffer, we need to adjust the positions of the statements
+	// to account for the added line of code.
+	// This is necessary to ensure that autofree can properly insert string declarations
+	// in the correct positions, considering the surgically made changes.
+	for index, stmt_pos in g.stmt_path_pos {
+		if stmt_pos >= pos {
+			g.stmt_path_pos[index] += s.len + 1
+		}
+	}
 }

vlib/v/slow_tests/valgrind/multiple_fn_calls.v

@@ -0,0 +1,13 @@
+import strconv
+
+fn color_code_to_rgb(color string) []int {
+	clr := color.replace('#', '')
+	return [int(strconv.parse_int(clr[0..2], 16, 0) or { return [0, 0, 0] }),
+		int(strconv.parse_int(clr[2..4], 16, 0) or { return [0, 0, 0] }),
+		int(strconv.parse_int(clr[4..6],
+			16, 0) or { return [0, 0, 0] })]
+}
+
+fn main() {
+	dump(color_code_to_rgb('#abcdef'))
+}

vlib/v/slow_tests/valgrind/valgrind_test.v

@@ -27,6 +27,7 @@ const skip_valgrind_files = [
 	'vlib/v/slow_tests/valgrind/struct_field.v',
 	'vlib/v/slow_tests/valgrind/fn_returning_string_param.v',
 	'vlib/v/slow_tests/valgrind/fn_with_return_should_free_local_vars.v',
+	'vlib/v/slow_tests/valgrind/multiple_fn_calls.v',
 	'vlib/v/slow_tests/valgrind/option_simple.v',
 	'vlib/v/slow_tests/valgrind/string_plus_string_plus.v',
 	'vlib/v/slow_tests/valgrind/import_x_json2.v',