[PATCH] D132906: [Clang] Fix lambda CheckForDefaultedFunction(...) so that it checks the CXXMethodDecl is a special member function before attempting to call DefineDefaultedFunction(...)

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik created this revision.
shafik added reviewers: erichkeane, aaron.ballman.
Herald added a project: All.
shafik requested review of this revision.

In `Sema::CheckCompletedCXXClass(...)` It used a lambda `CheckForDefaultedFunction` the `CXXMethodDecl` passed to `CheckForDefaultedFunction` may not be a special member function and so before attempting to apply functions that only apply to special member functions it needs to check. It fails to do this before calling `DefineDefaultedFunction(...)`. This PR adds that check and test to verify we no longer crash.

This fixes https://github.com/llvm/llvm-project/issues/57431


https://reviews.llvm.org/D132906

Files:
  clang/lib/Sema/SemaDeclCXX.cpp
  clang/test/SemaCXX/constant-expression-cxx2a.cpp


Index: clang/test/SemaCXX/constant-expression-cxx2a.cpp
===================================================================
--- clang/test/SemaCXX/constant-expression-cxx2a.cpp
+++ clang/test/SemaCXX/constant-expression-cxx2a.cpp
@@ -1473,3 +1473,13 @@
   }
   static_assert(g()); // expected-error {{constant expression}} expected-note {{in call}}
 }
+
+namespace GH57431 {
+class B{
+  virtual int constexpr f() = 0;
+};
+
+class D : B{
+  virtual int constexpr f() = default; // expected-error {{only special member functions and comparison operators may be defaulted}}
+};
+}
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -6954,7 +6954,8 @@
     // Define defaulted constexpr virtual functions that override a base class
     // function right away.
     // FIXME: We can defer doing this until the vtable is marked as used.
-    if (M->isDefaulted() && M->isConstexpr() && M->size_overridden_methods())
+    if (CSM != CXXInvalid && M->isDefaulted() && M->isConstexpr() &&
+        M->size_overridden_methods())
       DefineDefaultedFunction(*this, M, M->getLocation());
 
     if (!Incomplete)


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