[clang] d080f78 - [Clang] Fixed a crash when __PRETTY_FUNCTION__ or __FUNCSIG__ (clang-cl) appears in the trailing return type of the lambda (#122611)

[via cfe-commits]

Author: TilakChad
Date: 2025-01-12T15:42:04+01:00
New Revision: d080f78772acf9de4961b89062c02fdd5f82186a

URL: https://github.com/llvm/llvm-project/commit/d080f78772acf9de4961b89062c02fdd5f82186a
DIFF: https://github.com/llvm/llvm-project/commit/d080f78772acf9de4961b89062c02fdd5f82186a.diff

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

The (function) type of the lambda function is null while parsing
trailing return type. The type is filled-in when the lambda body is
entered. So, resolving `__PRETTY_FUNCTION__` before the lambda body is
entered causes the crash.

Fixes #121274.

Added: 
    clang/test/SemaCXX/crash-GH121274.cpp

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/AST/Expr.cpp

Removed: 
    


################################################################################
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 5331357b5d1fef..f6a4ed970cb23f 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -774,7 +774,15 @@ 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>();
+
+    // Bail out if the type of the function has not been set yet.
+    // This can notably happen in the trailing return type of a lambda
+    // expression.
+    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
+}