[clang] [Clang] Fixed a crash when __PRETTY_FUNCTION__ or __FUNCSIG__ (clang-cl) appears in the trailing return type of the lambda (PR #122611)

[via cfe-commits]

https://github.com/TilakChad updated https://github.com/llvm/llvm-project/pull/122611

>From 4e5935f6631f0f0cd828559ec29ed931bc0333d3 Mon Sep 17 00:00:00 2001
From: Tilak Chad <tilakchad111 at gmail.com>
Date: Sun, 12 Jan 2025 00:03:32 +0545
Subject: [PATCH 1/2] [Clang] Fixed a crash when __PRETTY_FUNCTION__ or
 __FUNCSIG__ (clang-cl) appears in the trailing return type of the lambda

---
 clang/lib/AST/Expr.cpp                |  7 ++++++-
 clang/test/SemaCXX/crash-GH121274.cpp | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/SemaCXX/crash-GH121274.cpp

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 5331357b5d1fef..0caff41c8a8cf6 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -774,7 +774,12 @@ std::string PredefinedExpr::ComputeName(PredefinedIdentKind IK,
     const FunctionDecl *Decl = FD;
     if (const FunctionDecl* Pattern = FD->getTemplateInstantiationPattern())
       Decl = Pattern;
-    const FunctionType *AFT = Decl->getType()->getAs<FunctionType>();
+
+    const Type *Ty = Decl->getType().getTypePtrOrNull();
+    if (!Ty)
+      return "";
+
+    const FunctionType *AFT = Ty->getAs<FunctionType>();
     const FunctionProtoType *FT = nullptr;
     if (FD->hasWrittenPrototype())
       FT = dyn_cast<FunctionProtoType>(AFT);
diff --git a/clang/test/SemaCXX/crash-GH121274.cpp b/clang/test/SemaCXX/crash-GH121274.cpp
new file mode 100644
index 00000000000000..28677a0949bf9e
--- /dev/null
+++ b/clang/test/SemaCXX/crash-GH121274.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+// expected-no-diagnostics
+
+// Do not crash when __PRETTY_FUNCTION__ appears in the trailing return type of the lambda
+void foo() {
+	[]() -> decltype(static_cast<const char*>(__PRETTY_FUNCTION__)) {
+		return nullptr;
+	}();
+
+#ifdef MS
+	[]() -> decltype(static_cast<const char*>(__FUNCSIG__)) {
+		return nullptr;
+	}();
+#endif
+}

>From cea9b5dc4b8440d738609abab93eb6fdfd0eead6 Mon Sep 17 00:00:00 2001
From: Tilak Chad <tilakchad111 at gmail.com>
Date: Sun, 12 Jan 2025 11:47:10 +0545
Subject: [PATCH 2/2] [Clang] Added comment and updated the clang release notes

---
 clang/docs/ReleaseNotes.rst | 1 +
 clang/lib/AST/Expr.cpp      | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 197b3692b8a181..a14fb189c8e132 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -926,6 +926,7 @@ Bug Fixes to C++ Support
   (`LWG3929 <https://wg21.link/LWG3929>`__.) (#GH121278)
 - Clang now identifies unexpanded parameter packs within the type constraint on a non-type template parameter. (#GH88866)
 - Fixed an issue while resolving type of expression indexing into a pack of values of non-dependent type (#GH121242)
+- Fixed a crash when __PRETTY_FUNCTION__ or __FUNCSIG__ (clang-cl) appears in the trailing return type of the lambda (#GH121274)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 0caff41c8a8cf6..b5dfc4bfe6dcb8 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -775,6 +775,9 @@ std::string PredefinedExpr::ComputeName(PredefinedIdentKind IK,
     if (const FunctionDecl* Pattern = FD->getTemplateInstantiationPattern())
       Decl = Pattern;
 
+    // The type may not be fully initialized at this point.
+    // For example, in the trailing return type context of the lambda
+    // expression.
     const Type *Ty = Decl->getType().getTypePtrOrNull();
     if (!Ty)
       return "";