From 95f27d11022a82a0d23931d1e8240fde42ae35cc Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 14 Apr 2026 23:02:18 +0300
Subject: [PATCH] cgen: fix cgen error with `-cstrict -cc clang` and defer in
 match branch (fixes #19092)

---
 vlib/v/gen/c/fn.v                             | 14 ++++++++-
 .../defer_fn_match_branch_capture.out         |  3 ++
 .../testdata/defer_fn_match_branch_capture.vv | 30 +++++++++++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/gen/c/testdata/defer_fn_match_branch_capture.out
 create mode 100644 vlib/v/gen/c/testdata/defer_fn_match_branch_capture.vv

diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index 8c8a1e883..df5351983 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -1176,7 +1176,19 @@ fn (mut g Gen) gen_fn_decl(node &ast.FnDecl, skip bool) {
 						if info.is_volatile {
 							g.write('volatile ')
 						}
-						g.writeln('${g.styp(info.typ)}${deref} ${c_name(var.name)};')
+						decl_typ := if deref == '*' {
+							info.typ.ref()
+						} else {
+							info.typ
+						}
+						default_expr := g.type_default(decl_typ)
+						if g.type_default_vars.len > 0 {
+							for decl in g.type_default_vars.str().trim_right('\n').split_into_lines() {
+								g.writeln(decl)
+							}
+							g.type_default_vars.clear()
+						}
+						g.writeln('${g.styp(info.typ)}${deref} ${c_name(var.name)} = ${default_expr};')
 					}
 				}
 			}
diff --git a/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.out b/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.out
new file mode 100644
index 000000000..98ca40704
--- /dev/null
+++ b/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.out
@@ -0,0 +1,3 @@
+42 false
+123 false
+42 false
diff --git a/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.vv b/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.vv
new file mode 100644
index 000000000..6bb569cf5
--- /dev/null
+++ b/vlib/v/gen/c/testdata/defer_fn_match_branch_capture.vv
@@ -0,0 +1,30 @@
+// vtest vflags: -cstrict -cc clang
+
+struct Object {
+mut:
+	context bool
+}
+
+fn (mut o Object) f(x int) int {
+	match x {
+		0 {
+			old := o.context
+			defer(fn) {
+				o.context = old
+			}
+			o.context = true
+		}
+		1 {
+			return 123
+		}
+		else {}
+	}
+	return 42
+}
+
+fn main() {
+	mut o := Object{}
+	println('${o.f(0)} ${o.context}')
+	println('${o.f(1)} ${o.context}')
+	println('${o.f(2)} ${o.context}')
+}
-- 
2.39.5