[clang] d8c8c8c - [clang][Interp] Diagnose dummy assignments differently

[Timm Bäder via cfe-commits]

Author: Timm Bäder
Date: 2024-05-24T16:40:38+02:00
New Revision: d8c8c8c7b91ce51f3e2fc088a5fd365b23cd9889

URL: https://github.com/llvm/llvm-project/commit/d8c8c8c7b91ce51f3e2fc088a5fd365b23cd9889
DIFF: https://github.com/llvm/llvm-project/commit/d8c8c8c7b91ce51f3e2fc088a5fd365b23cd9889.diff

LOG: [clang][Interp] Diagnose dummy assignments differently

Incremental change here, but a step in the right direction. Before,
an assignment to a dummy variable was diagnosed as a "read of a
non-const variable".

Added: 
    

Modified: 
    clang/lib/AST/Interp/Interp.cpp
    clang/lib/AST/Interp/Interp.h
    clang/lib/AST/Interp/InterpBuiltin.cpp
    clang/test/AST/Interp/cxx03.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/AST/Interp/Interp.cpp b/clang/lib/AST/Interp/Interp.cpp
index de5390596d632..145fa65791da2 100644
--- a/clang/lib/AST/Interp/Interp.cpp
+++ b/clang/lib/AST/Interp/Interp.cpp
@@ -457,7 +457,7 @@ bool CheckLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!CheckConstant(S, OpPC, Ptr))
     return false;
 
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Read))
     return false;
   if (!CheckExtern(S, OpPC, Ptr))
     return false;
@@ -477,7 +477,7 @@ bool CheckLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
 bool CheckStore(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!CheckLive(S, OpPC, Ptr, AK_Assign))
     return false;
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Assign))
     return false;
   if (!CheckExtern(S, OpPC, Ptr))
     return false;
@@ -660,7 +660,8 @@ bool CheckDeclRef(InterpState &S, CodePtr OpPC, const DeclRefExpr *DR) {
   return diagnoseUnknownDecl(S, OpPC, D);
 }
 
-bool CheckDummy(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
+bool CheckDummy(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
+                AccessKinds AK) {
   if (!Ptr.isDummy())
     return true;
 
@@ -669,7 +670,15 @@ bool CheckDummy(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!D)
     return false;
 
-  return diagnoseUnknownDecl(S, OpPC, D);
+  if (AK == AK_Read || AK == AK_Increment || AK == AK_Decrement)
+    return diagnoseUnknownDecl(S, OpPC, D);
+
+  assert(AK == AK_Assign);
+  if (S.getLangOpts().CPlusPlus11) {
+    const SourceInfo &E = S.Current->getSource(OpPC);
+    S.FFDiag(E, diag::note_constexpr_modify_global);
+  }
+  return false;
 }
 
 bool CheckNonNullArgs(InterpState &S, CodePtr OpPC, const Function *F,

diff  --git a/clang/lib/AST/Interp/Interp.h b/clang/lib/AST/Interp/Interp.h
index bcb6fb4d65218..eca1792e64718 100644
--- a/clang/lib/AST/Interp/Interp.h
+++ b/clang/lib/AST/Interp/Interp.h
@@ -56,7 +56,8 @@ bool CheckLive(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
                AccessKinds AK);
 
 /// Checks if a pointer is a dummy pointer.
-bool CheckDummy(InterpState &S, CodePtr OpPC, const Pointer &Ptr);
+bool CheckDummy(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
+                AccessKinds AK);
 
 /// Checks if a pointer is null.
 bool CheckNull(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
@@ -588,7 +589,7 @@ bool IncDecHelper(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool Inc(InterpState &S, CodePtr OpPC) {
   const Pointer &Ptr = S.Stk.pop<Pointer>();
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Increment))
     return false;
   if (!CheckInitialized(S, OpPC, Ptr, AK_Increment))
     return false;
@@ -602,7 +603,7 @@ bool Inc(InterpState &S, CodePtr OpPC) {
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool IncPop(InterpState &S, CodePtr OpPC) {
   const Pointer &Ptr = S.Stk.pop<Pointer>();
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Increment))
     return false;
   if (!CheckInitialized(S, OpPC, Ptr, AK_Increment))
     return false;
@@ -617,7 +618,7 @@ bool IncPop(InterpState &S, CodePtr OpPC) {
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool Dec(InterpState &S, CodePtr OpPC) {
   const Pointer &Ptr = S.Stk.pop<Pointer>();
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Decrement))
     return false;
   if (!CheckInitialized(S, OpPC, Ptr, AK_Decrement))
     return false;
@@ -631,7 +632,7 @@ bool Dec(InterpState &S, CodePtr OpPC) {
 template <PrimType Name, class T = typename PrimConv<Name>::T>
 bool DecPop(InterpState &S, CodePtr OpPC) {
   const Pointer &Ptr = S.Stk.pop<Pointer>();
-  if (!CheckDummy(S, OpPC, Ptr))
+  if (!CheckDummy(S, OpPC, Ptr, AK_Decrement))
     return false;
   if (!CheckInitialized(S, OpPC, Ptr, AK_Decrement))
     return false;

diff  --git a/clang/lib/AST/Interp/InterpBuiltin.cpp b/clang/lib/AST/Interp/InterpBuiltin.cpp
index 565c85bc2e0c2..00206d09c113d 100644
--- a/clang/lib/AST/Interp/InterpBuiltin.cpp
+++ b/clang/lib/AST/Interp/InterpBuiltin.cpp
@@ -214,7 +214,7 @@ static bool interp__builtin_strlen(InterpState &S, CodePtr OpPC,
   if (!CheckLive(S, OpPC, StrPtr, AK_Read))
     return false;
 
-  if (!CheckDummy(S, OpPC, StrPtr))
+  if (!CheckDummy(S, OpPC, StrPtr, AK_Read))
     return false;
 
   assert(StrPtr.getFieldDesc()->isPrimitiveArray());

diff  --git a/clang/test/AST/Interp/cxx03.cpp b/clang/test/AST/Interp/cxx03.cpp
index b6aaf0840cfb3..70ae4134842b5 100644
--- a/clang/test/AST/Interp/cxx03.cpp
+++ b/clang/test/AST/Interp/cxx03.cpp
@@ -24,3 +24,8 @@ namespace NonLValueMemberExpr {
 
   const int &TT1::subobj_init = PODType().value;
 }
+
+void LambdaAccessingADummy() {
+  int d;
+  int a9[1] = {[d = 0] = 1}; // both-error {{is not an integral constant expression}}
+}