From 5db3330069617c4be85df44ffce5ea0538812f53 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 26 Feb 2026 11:42:16 +0300
Subject: [PATCH] cgen: fix -autofree C compiler error (fixes #23527)

---
 vlib/v/gen/c/cgen.v                           |  2 +-
 vlib/v/gen/c/fn.v                             | 18 ++++++++++--
 ...tofree_compare_strings_if_expr.c.must_have |  4 +++
 .../autofree_compare_strings_if_expr.vv       | 29 +++++++++++++++++++
 4 files changed, 49 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.vv

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index fcc36e78d..f7fdab2e9 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -4021,7 +4021,7 @@ fn (mut g Gen) expr(node_ ast.Expr) {
 			}
 			g.call_expr(node)
 			if g.is_autofree && !g.is_builtin_mod && !g.is_js_call && g.strs_to_free0.len == 0
-				&& !g.is_autofree_tmp && !g.inside_lambda {
+				&& !g.is_autofree_tmp && !g.inside_lambda && g.inside_ternary == 0 {
 				// if len != 0, that means we are handling call expr inside call expr (arg)
 				// and it'll get messed up here, since it's handled recursively in autofree_call_pregen()
 				// so just skip it
diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index b68f36405..9cc8e34d4 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -2414,7 +2414,6 @@ fn (mut g Gen) autofree_call_pregen(node ast.CallExpr) {
 		if arg.expr is ast.CallExpr && arg.expr.is_method && arg.expr.left is ast.CallExpr {
 			g.is_autofree = false
 		}
-
 		tmp_arg_init := g.autofree_tmp_arg_init_stmt(s, arg.expr)
 		g.is_autofree = old_is_autofree
 		g.is_autofree_tmp = false
@@ -2637,7 +2636,7 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 			}
 		}
 		use_tmp_var_autofree := g.is_autofree && arg.typ == ast.string_type && arg.is_tmp_autofree
-			&& !g.inside_const && !g.is_builtin_mod
+			&& !g.inside_const && !g.is_builtin_mod && g.inside_ternary == 0
 		// g.write('/* af=${arg.is_tmp_autofree} */')
 		// some c fn definitions dont have args (cfns.v) or are not updated in checker
 		// when these are fixed we wont need this check
@@ -2653,7 +2652,20 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 				name := '_arg_expr_${fn_name}_${i + 1}_${node.pos.pos}'
 				scope := g.file.scope.innermost(node.pos.pos)
 				if !g.is_autofree_tmp || scope.known_var(name) {
-					g.write('/*autofree arg*/' + name)
+					tmp_arg := ast.CallArg{
+						typ:    arg.typ
+						is_mut: arg.is_mut
+						expr:   ast.Ident{
+							name: name
+							kind: .variable
+							info: ast.IdentVar{
+								typ:    arg.typ
+								is_mut: arg.is_mut
+							}
+						}
+					}
+					g.write('/*autofree arg*/')
+					g.ref_or_deref_arg(tmp_arg, expected_types[i], node.language, is_smartcast)
 					wrote_tmp_arg = true
 				}
 			}
diff --git a/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.c.must_have b/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.c.must_have
new file mode 100644
index 000000000..f4338018a
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.c.must_have
@@ -0,0 +1,4 @@
+builtin__compare_strings(/*autofree arg*/(voidptr)&_arg_expr_compare_strings_1_
+builtin__compare_strings(ADDR(string, builtin__string_to_lower(a)), ADDR(string, builtin__string_to_lower(b)))
+string _arg_expr_main_right_pad_end_1_
+right_pad_end(/*autofree arg*/_arg_expr_main_right_pad_end_1_
diff --git a/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.vv b/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.vv
new file mode 100644
index 000000000..e3780939f
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_compare_strings_if_expr.vv
@@ -0,0 +1,29 @@
+// vtest vflags: -autofree
+import os
+
+fn string_compare(a string, b string, ignore_case bool) int {
+	return match ignore_case {
+		true { compare_strings(a.to_lower(), b.to_lower()) }
+		else { compare_strings(a, b) }
+	}
+}
+
+fn right_pad_end(s string, width int) string {
+	pad := width - s.len
+	if pad > 0 {
+		return s + ' '.repeat(pad)
+	}
+	return s
+}
+
+fn main() {
+	ext_cmp := compare_strings(os.file_ext('foo.v'), os.file_ext('bar.md'))
+	println(ext_cmp)
+	println(string_compare('Ab', 'aB', true))
+	show_header := true
+	title := 'name'
+	mut buffer := '>'
+	buffer += right_pad_end(if show_header { title } else { '' }, 6)
+	buffer += '<'
+	println(buffer)
+}
-- 
2.39.5