From d86b523aa920e239028bbb91546eb7591051f4c8 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 26 Feb 2026 11:31:32 +0300
Subject: [PATCH] cgen: fix C error when passing expression directly as
 argument instead of variable (fixes #19152)

---
 vlib/v/gen/c/fn.v                             | 22 +++++++++++++++++--
 vlib/v/gen/c/testdata/autofree_ifexpr_arg.out |  1 +
 vlib/v/gen/c/testdata/autofree_ifexpr_arg.vv  |  9 ++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/autofree_ifexpr_arg.out
 create mode 100644 vlib/v/gen/c/testdata/autofree_ifexpr_arg.vv

diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index ec974fe13..b68f36405 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -2325,6 +2325,24 @@ fn (mut g Gen) gen_trace_call(node ast.CallExpr, name string) {
 	}
 }
 
+fn (mut g Gen) autofree_tmp_arg_init_stmt(prepend string, expr ast.Expr) string {
+	saved_out := g.out
+	saved_stmt_path_pos := g.stmt_path_pos.clone()
+	saved_empty_line := g.empty_line
+	saved_indent := g.indent
+	g.out = strings.new_builder(256)
+	g.stmt_path_pos = [0]
+	g.empty_line = true
+	g.indent = 0
+	defer {
+		g.out = saved_out
+		g.stmt_path_pos = saved_stmt_path_pos
+		g.empty_line = saved_empty_line
+		g.indent = saved_indent
+	}
+	return g.expr_string_surround(prepend, expr, ';').trim_space()
+}
+
 fn (mut g Gen) autofree_call_pregen(node ast.CallExpr) {
 	// g.writeln('// autofree_call_pregen()')
 	// Create a temporary var before fn call for each argument in order to free it (only if it's a complex expression,
@@ -2397,10 +2415,10 @@ fn (mut g Gen) autofree_call_pregen(node ast.CallExpr) {
 			g.is_autofree = false
 		}
 
-		s = g.expr_string_surround(s, arg.expr, ';').trim_space()
+		tmp_arg_init := g.autofree_tmp_arg_init_stmt(s, arg.expr)
 		g.is_autofree = old_is_autofree
 		g.is_autofree_tmp = false
-		g.strs_to_free0 << s
+		g.strs_to_free0 << tmp_arg_init
 		// This tmp arg var will be freed with the rest of the vars at the end of the scope.
 	}
 }
diff --git a/vlib/v/gen/c/testdata/autofree_ifexpr_arg.out b/vlib/v/gen/c/testdata/autofree_ifexpr_arg.out
new file mode 100644
index 000000000..d00491fd7
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_ifexpr_arg.out
@@ -0,0 +1 @@
+1
diff --git a/vlib/v/gen/c/testdata/autofree_ifexpr_arg.vv b/vlib/v/gen/c/testdata/autofree_ifexpr_arg.vv
new file mode 100644
index 000000000..f5fac0f94
--- /dev/null
+++ b/vlib/v/gen/c/testdata/autofree_ifexpr_arg.vv
@@ -0,0 +1,9 @@
+// vtest vflags: -autofree
+import strings
+
+fn main() {
+	mut sb := strings.new_builder(16)
+	hour := 13
+	sb.write_string(if hour > 12 { hour - 12 } else { hour }.str())
+	println(sb.str())
+}
-- 
2.39.5