[llvm-branch-commits] [clang] f6fb6a9 - [clang][ExprConst] Fix crash on uninitialized array subobject (#67817)

[Tobias Hieta via llvm-branch-commits]

Author: Takuya Shimizu
Date: 2023-10-30T12:59:49+01:00
New Revision: f6fb6a996c7fe7962bbfbc7bbdb42d690b1f630f

URL: https://github.com/llvm/llvm-project/commit/f6fb6a996c7fe7962bbfbc7bbdb42d690b1f630f
DIFF: https://github.com/llvm/llvm-project/commit/f6fb6a996c7fe7962bbfbc7bbdb42d690b1f630f.diff

LOG: [clang][ExprConst] Fix crash on uninitialized array subobject (#67817)

https://reviews.llvm.org/D146358 was assuming that all subobjects have
their own name (`SubobjectDecl`), but it was not true for array
elements.

Fixes https://github.com/llvm/llvm-project/issues/67317

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/include/clang/Basic/DiagnosticASTKinds.td
    clang/lib/AST/ExprConstant.cpp
    clang/lib/AST/Interp/Interp.cpp
    clang/test/SemaCXX/constant-expression-cxx2a.cpp
    clang/test/SemaCXX/eval-crashes.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 88844ad9b4c5566..a06302531bc2eef 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -719,6 +719,8 @@ Bug Fixes in This Version
   points (i.e., uses function descriptor objects instead).
 - Fixes a ``clang-17`` regression where ``LLVM_UNREACHABLE_OPTIMIZE=OFF``
   cannot be used with ``Release`` mode builds. (`#68237 <https://github.com/llvm/llvm-project/issues/68237>`_).
+- Fix crash from constexpr evaluator evaluating uninitialized arrays as rvalue.
+  Fixes (`#67317 <https://github.com/llvm/llvm-project/issues/67317>`_)
 - No longer use C++ ``thread_local`` semantics in C23 when using
   ``thread_local`` instead of ``_Thread_local``.
   Fixes (`#70068 <https://github.com/llvm/llvm-project/issues/70068>`_) and

diff  --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index 0794ed7ba683730..694e6a5840bcb8b 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -69,7 +69,7 @@ def note_consteval_address_accessible : Note<
   "%select{pointer|reference}0 to a consteval declaration "
   "is not a constant expression">;
 def note_constexpr_uninitialized : Note<
-  "subobject %0 is not initialized">;
+  "subobject %select{of type |}0%1 is not initialized">;
 def note_constexpr_uninitialized_base : Note<
   "constructor of base class %0 is not called">;
 def note_constexpr_static_local : Note<

diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index c62044f36194c68..99ae88a6cd69241 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2379,10 +2379,15 @@ static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                   const FieldDecl *SubobjectDecl,
                                   CheckedTemporaries &CheckedTemps) {
   if (!Value.hasValue()) {
-    assert(SubobjectDecl && "SubobjectDecl shall be non-null");
-    Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized) << SubobjectDecl;
-    Info.Note(SubobjectDecl->getLocation(),
-              diag::note_constexpr_subobject_declared_here);
+    if (SubobjectDecl) {
+      Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
+          << /*(name)*/ 1 << SubobjectDecl;
+      Info.Note(SubobjectDecl->getLocation(),
+                diag::note_constexpr_subobject_declared_here);
+    } else {
+      Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
+          << /*of type*/ 0 << Type;
+    }
     return false;
   }
 

diff  --git a/clang/lib/AST/Interp/Interp.cpp b/clang/lib/AST/Interp/Interp.cpp
index 4917f43f9512ec2..59108b8575774d7 100644
--- a/clang/lib/AST/Interp/Interp.cpp
+++ b/clang/lib/AST/Interp/Interp.cpp
@@ -382,7 +382,8 @@ bool CheckPure(InterpState &S, CodePtr OpPC, const CXXMethodDecl *MD) {
 static void DiagnoseUninitializedSubobject(InterpState &S, const SourceInfo &SI,
                                            const FieldDecl *SubObjDecl) {
   assert(SubObjDecl && "Subobject declaration does not exist");
-  S.FFDiag(SI, diag::note_constexpr_uninitialized) << SubObjDecl;
+  S.FFDiag(SI, diag::note_constexpr_uninitialized)
+      << /*(name)*/ 1 << SubObjDecl;
   S.Note(SubObjDecl->getLocation(),
          diag::note_constexpr_subobject_declared_here);
 }

diff  --git a/clang/test/SemaCXX/constant-expression-cxx2a.cpp b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
index 09f17d5b3894998..e4d97dcb73562d6 100644
--- a/clang/test/SemaCXX/constant-expression-cxx2a.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
@@ -1492,3 +1492,9 @@ class B{
 class D : B{}; // expected-error {{deleted function '~D' cannot override a non-deleted function}}
 // expected-note at -1 {{destructor of 'D' is implicitly deleted because base class 'B' has an inaccessible destructor}}
 }
+
+namespace GH67317 {
+  constexpr unsigned char a = // expected-error {{constexpr variable 'a' must be initialized by a constant expression}} \
+                              // expected-note {{subobject of type 'const unsigned char' is not initialized}}
+    __builtin_bit_cast(unsigned char, *new char[3][1]);
+};

diff  --git a/clang/test/SemaCXX/eval-crashes.cpp b/clang/test/SemaCXX/eval-crashes.cpp
index 3e59ad31c559da8..ac04b113f99b7aa 100644
--- a/clang/test/SemaCXX/eval-crashes.cpp
+++ b/clang/test/SemaCXX/eval-crashes.cpp
@@ -54,3 +54,10 @@ namespace pr33140_10 {
   int a(const int &n = 0);
   bool b() { return a() == a(); }
 }
+
+namespace GH67317 {
+struct array {
+  int (&data)[2];
+  array() : data(*new int[1][2]) {}
+};
+}