[clang] 8f768ec - [Clang] Fix crash when visting a fold expression in a default argument (#67514)

[via cfe-commits]

Author: Shafik Yaghmour
Date: 2023-09-28T12:20:22-07:00
New Revision: 8f768ec00592009cda496c8f7bfeef013887b5f3

URL: https://github.com/llvm/llvm-project/commit/8f768ec00592009cda496c8f7bfeef013887b5f3
DIFF: https://github.com/llvm/llvm-project/commit/8f768ec00592009cda496c8f7bfeef013887b5f3.diff

LOG: [Clang] Fix crash when visting a fold expression in a default argument (#67514)

CheckDefaultArgumentVisitor::Visit(...) assumes that the children of
Expr will not be NULL. This is not a valid assumption and when we have a
CXXFoldExpr the children can be NULL and this causes a crash.

Fixes: https://github.com/llvm/llvm-project/issues/67395

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Sema/SemaDeclCXX.cpp
    clang/test/SemaTemplate/cxx1z-fold-expressions.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f314c9c72fa28b7..1d74c492845a6c3 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -363,6 +363,10 @@ Bug Fixes to C++ Support
   in the enclosing expression of a lambda expression with a noexcept specifier.
   (`#67492 <https://github.com/llvm/llvm-project/issues/67492>`_)
 
+- Fix crash when fold expression was used in the initialization of default
+  argument. Fixes:
+  (`#67395 <https://github.com/llvm/llvm-project/issues/67395>`_)
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.

diff  --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 0091e0ecf6f3986..302e944d5d74f1c 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -86,7 +86,8 @@ class CheckDefaultArgumentVisitor
 bool CheckDefaultArgumentVisitor::VisitExpr(const Expr *Node) {
   bool IsInvalid = false;
   for (const Stmt *SubStmt : Node->children())
-    IsInvalid |= Visit(SubStmt);
+    if (SubStmt)
+      IsInvalid |= Visit(SubStmt);
   return IsInvalid;
 }
 

diff  --git a/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp b/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
index 518eaf0e05239e0..47a252eb335f6e5 100644
--- a/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
+++ b/clang/test/SemaTemplate/cxx1z-fold-expressions.cpp
@@ -124,3 +124,11 @@ namespace PR30738 {
   int test_h3 = h<struct X>(1, 2, 3);
   N::S test_h4 = h<struct X>(N::S(), N::S(), N::S()); // expected-note {{instantiation of}}
 }
+
+namespace GH67395 {
+template <typename>
+bool f();
+
+template <typename... T>
+void g(bool = (f<T>() || ...));
+}