[clang] a4edc2c - Constexpr evaluator should treat [[gnu::weak]] member pointer comparisons as evaluation failure

[Aaron Ballman via cfe-commits]

Author: Takuya Shimizu
Date: 2023-04-17T09:50:46-04:00
New Revision: a4edc2c9fa35a763fc5f4c9cf6383096a13a9cf6

URL: https://github.com/llvm/llvm-project/commit/a4edc2c9fa35a763fc5f4c9cf6383096a13a9cf6
DIFF: https://github.com/llvm/llvm-project/commit/a4edc2c9fa35a763fc5f4c9cf6383096a13a9cf6.diff

LOG: Constexpr evaluator should treat [[gnu::weak]] member pointer comparisons as evaluation failure

This patch fixes the wrong signal from the constexpr evaluator that
[[gnu::weak]] member pointer comparison is valid, while it is emitting
notes on them.

I found a crashing case fixed by this change and added it as a test
case: https://godbolt.org/z/8391fGjGn

I noticed this while I was working on D146358.

Differential Revision: https://reviews.llvm.org/D148419

Added: 
    clang/test/SemaCXX/crash-lambda-weak-attr.cpp

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

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 9c8a0e1faa32..05189bfb6aba 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -312,6 +312,8 @@ Bug Fixes in This Version
   (`#61417 <https://github.com/llvm/llvm-project/issues/61417>`_)
 - Fix crash after suggesting typo correction to constexpr if condition.
   (`#61885 <https://github.com/llvm/llvm-project/issues/61885>`_)
+- Clang constexpr evaluator now treats comparison of [[gnu::weak]]-attributed
+  member pointer as an invalid expression.
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index fbe92d054d6b..6bfb3a37b243 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -13142,12 +13142,12 @@ EvaluateComparisonBinaryOperator(EvalInfo &Info, const BinaryOperator *E,
     if (LHSValue.getDecl() && LHSValue.getDecl()->isWeak()) {
       Info.FFDiag(E, diag::note_constexpr_mem_pointer_weak_comparison)
           << LHSValue.getDecl();
-      return true;
+      return false;
     }
     if (RHSValue.getDecl() && RHSValue.getDecl()->isWeak()) {
       Info.FFDiag(E, diag::note_constexpr_mem_pointer_weak_comparison)
           << RHSValue.getDecl();
-      return true;
+      return false;
     }
 
     // C++11 [expr.eq]p2:

diff  --git a/clang/test/SemaCXX/crash-lambda-weak-attr.cpp b/clang/test/SemaCXX/crash-lambda-weak-attr.cpp
new file mode 100644
index 000000000000..28a516942393
--- /dev/null
+++ b/clang/test/SemaCXX/crash-lambda-weak-attr.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct Weak {
+    [[gnu::weak]]void weak_method();
+};
+static_assert([](){ return &Weak::weak_method != nullptr; }()); // expected-error {{static assertion expression is not an integral constant expression}} \
+                                                                // expected-note {{comparison against pointer to weak member 'Weak::weak_method' can only be performed at runtime}} \
+                                                                // expected-note {{in call to}}
+