[Clang] Fix lambda CheckForDefaultedFunction(...) so that it checks the CXXMethodDecl...

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

Differential Revision: https://reviews.llvm.org/D132906

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f946018..944d88d 100644 (file)
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -86,6 +86,9 @@ Bug Fixes
   `Issue 57387 <https://github.com/llvm/llvm-project/issues/57387>`_.
 - Fix a crash when emitting a concept-related diagnostic. This fixes
   `Issue 57415 <https://github.com/llvm/llvm-project/issues/57415>`_.
+- Fix a crash when attempting to default a virtual constexpr non-special member
+  function in a derived class. This fixes
+  `Issue 57431 <https://github.com/llvm/llvm-project/issues/57431>`_
 
 
 Improvements to Clang's diagnostics

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 198de68..04d06c1 100644 (file)
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -6954,7 +6954,8 @@ void Sema::CheckCompletedCXXClass(Scope *S, CXXRecordDecl *Record) {
     // 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)

diff --git a/clang/test/SemaCXX/constant-expression-cxx2a.cpp b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
index 6ebec5d..63ea429 100644 (file)
--- a/clang/test/SemaCXX/constant-expression-cxx2a.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
@@ -1473,3 +1473,13 @@ namespace PR45879 {
   }
   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}}
+};
+}