[llvm-branch-commits] [clang] release/23.x: [Clang][CodeGen] Fix crash in EmitParmDecl for bodyless destructors with -fextend-variable-liveness (#218830) (PR #221603)

[via llvm-branch-commits]

https://github.com/AZero13 created https://github.com/llvm/llvm-project/pull/221603

The fake-use coroutine check in EmitParmDecl calls FnDecl->getBody()->getStmtClass() without guarding against a null getBody(). This crashes when processing implicit parameters (e.g. should_call_delete) of MSVC deleting destructors whose base destructor is only declared, not defined.

>From 9cb39933030d5081fde92c2c1dfe0621e4615a9e Mon Sep 17 00:00:00 2001
From: AZero13 <gfunni234 at gmail.com>
Date: Wed, 26 Aug 2026 14:24:55 -0400
Subject: [PATCH] [Clang][CodeGen] Fix crash in EmitParmDecl for bodyless
 destructors with -fextend-variable-liveness (#218830)

The fake-use coroutine check in EmitParmDecl calls
FnDecl->getBody()->getStmtClass() without guarding against a null
getBody(). This crashes when processing implicit parameters (e.g.
should_call_delete) of MSVC deleting destructors whose base destructor
is only declared, not defined.
---
 clang/docs/ReleaseNotes.md                |  1 +
 clang/lib/CodeGen/CGDecl.cpp              |  2 +-
 clang/test/CodeGen/fake-use-msvc-dtor.cpp | 17 +++++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/fake-use-msvc-dtor.cpp

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index 6928e8ab4bffb..d3039f0091e91 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -998,6 +998,7 @@ latest release, please see the [Clang Web Site](https://clang.llvm.org) or the
 - Fixed a crash when passing one sized implicitly casted vector to a `abs` function. (#GH204777)
 - Fixed a crash when diagnosing an invalid out-of-line definition of a member class template. (#GH201490)
 - Fixed a crash in the parser when a missing semicolon after a tag definition is followed by a template-id not preceded by `::`. (#GH207992)
+- Fixed a crash when generating fake uses for parameters of bodyless destructors with `-fextend-variable-liveness`.
 
 ### OpenACC Specific Changes
 
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 29bc47130c4cd..e84e05e8ee0fd 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -2856,7 +2856,7 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
        &D == CXXABIThisDecl)) {
     // We don't emit fake uses for coroutine parameters, other than `this`.
     if (auto *FnDecl = dyn_cast_or_null<FunctionDecl>(CurCodeDecl);
-        &D == CXXABIThisDecl || !FnDecl ||
+        &D == CXXABIThisDecl || !FnDecl || !FnDecl->getBody() ||
         FnDecl->getBody()->getStmtClass() != Stmt::CoroutineBodyStmtClass) {
       if (shouldExtendLifetime(getContext(), CurCodeDecl, D, CXXABIThisDecl))
         EHStack.pushCleanup<FakeUse>(NormalFakeUse, DeclPtr);
diff --git a/clang/test/CodeGen/fake-use-msvc-dtor.cpp b/clang/test/CodeGen/fake-use-msvc-dtor.cpp
new file mode 100644
index 0000000000000..3988b4b2242ec
--- /dev/null
+++ b/clang/test/CodeGen/fake-use-msvc-dtor.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 %s -triple x86_64-pc-windows-msvc -emit-llvm -fextend-variable-liveness=all -O1 -mconstructor-aliases -o /dev/null
+// Verify that we do not crash when generating fake uses for parameters
+// of destructor declarations that have no body (the should_call_delete
+// implicit parameter in MSVC deleting destructors).
+
+struct A {
+  virtual ~A(void);
+};
+struct B {
+  virtual ~B(void);
+};
+
+struct C : A, B {};
+
+void foo() {
+  C c;
+}