From ce10c140c6b6975c5d543b8e6a5bac5bdd6a6939 Mon Sep 17 00:00:00 2001
From: Denys Smirnov <dennwc@pm.me>
Date: Sat, 9 Nov 2024 14:48:59 +0200
Subject: [PATCH] cxgo: Fix panic in switch with unreachable stmt. Fixes #80.

---
 c_stmt.go     |  7 ++++++-
 parse_test.go | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/c_stmt.go b/c_stmt.go
index 7723679..474fdec 100644
--- a/c_stmt.go
+++ b/c_stmt.go
@@ -358,7 +358,12 @@ func (s *CSwitchStmt) addStmts(stmts []CStmt) {
 				s.addStmts(sub)
 			}
 		} else {
-			last := s.Cases[len(s.Cases)-1]
+			ci := len(s.Cases) - 1
+			if ci < 0 {
+				// statement before any cases - ignore
+				continue
+			}
+			last := s.Cases[ci]
 			last.Stmts = append(last.Stmts, st)
 		}
 	}
diff --git a/parse_test.go b/parse_test.go
index b364ae6..cf59f5c 100644
--- a/parse_test.go
+++ b/parse_test.go
@@ -150,6 +150,62 @@ func foo(a int32) {
 		foo(6)
 	}
 }
+`,
+	},
+	{
+		name: "switch unreachable",
+		src: `
+void foo(int a) {
+	switch (a) {
+		a++;
+	case 1:
+		foo(1);
+		break;
+		a++;
+	case 2:
+		foo(2);
+	default:
+		foo(0);
+	case 3:
+		foo(3);
+		break;
+	case 4:
+	case 5:
+		foo(5);
+		return;
+		a++;
+	case 6:
+		foo(6);
+	}
+}
+`,
+		exp: `
+func foo(a int32) {
+	switch a {
+	case 1:
+		foo(1)
+		break
+		a++
+		fallthrough
+	case 2:
+		foo(2)
+		fallthrough
+	default:
+		foo(0)
+		fallthrough
+	case 3:
+		foo(3)
+	case 4:
+		fallthrough
+	case 5:
+		foo(5)
+		return
+		a++
+		fallthrough
+	case 6:
+		foo(6)
+	}
+}
 `,
 	},
 	{