[clang][Interp] Diagnose casts from void pointers

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -325,8 +325,11 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
 
     assert(isPtrType(*FromT));
     assert(isPtrType(*ToT));
-    if (FromT == ToT)
+    if (FromT == ToT) {
+      if (SubExpr->getType()->isVoidPointerType())
+        return this->visit(SubExpr) && this->emitVoidPtrCast(CE);
       return this->delegate(SubExpr);
+    }
 
     if (!this->visit(SubExpr))
       return false;

clang/lib/AST/Interp/Interp.h

@@ -1980,6 +1980,13 @@ static inline bool CastPointerIntegralAPS(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static inline bool VoidPtrCast(InterpState &S, CodePtr OpPC) {
+  const SourceInfo &E = S.Current->getSource(OpPC);
+  S.CCEDiag(E, diag::note_constexpr_invalid_cast)
+      << 2 << S.getLangOpts().CPlusPlus << S.Current->getRange(OpPC);
+  return true;
+}
+
 //===----------------------------------------------------------------------===//
 // Zero, Nullptr
 //===----------------------------------------------------------------------===//

clang/lib/AST/Interp/Opcodes.td

@@ -665,6 +665,7 @@ def CastPointerIntegralAPS : Opcode {
   let HasGroup = 0;
   let Args = [ArgUint32];
 }
+def VoidPtrCast : Opcode;
 
 def DecayPtr : Opcode {
   let Types = [PtrTypeClass, PtrTypeClass];

clang/test/AST/Interp/c.c

@@ -66,12 +66,10 @@ _Static_assert((&a - 100) != 0, ""); // pedantic-ref-warning {{is a GNU extensio
                                      // pedantic-ref-note {{-100 of non-array}} \
                                      // pedantic-expected-note {{-100 of non-array}}
 /// extern variable of a composite type.
-/// FIXME: The 'this conversion is not allowed' note is missing in the new interpreter.
 extern struct Test50S Test50;
 _Static_assert(&Test50 != (void*)0, ""); // all-warning {{always true}} \
-                                         // pedantic-ref-warning {{is a GNU extension}} \
-                                         // pedantic-ref-note {{this conversion is not allowed in a constant expression}} \
-                                         // pedantic-expected-warning {{is a GNU extension}}
+                                         // pedantic-warning {{is a GNU extension}} \
+                                         // pedantic-note {{this conversion is not allowed in a constant expression}}
 
 struct y {int x,y;};
 int a2[(intptr_t)&((struct y*)0)->y]; // all-warning {{folded to constant array}}

clang/test/Sema/constexpr-void-cast.c

@@ -1,8 +1,12 @@
 // RUN: %clang_cc1 -x c -fsyntax-only %s -verify=c -std=c11
 // RUN: %clang_cc1 -x c -fsyntax-only %s -pedantic -verify=c-pedantic -std=c11
+// RUN: %clang_cc1 -x c -fsyntax-only %s -verify=c -std=c11 -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -x c -fsyntax-only %s -pedantic -verify=c-pedantic -std=c11 -fexperimental-new-constant-interpreter
 //
 // RUN: %clang_cc1 -x c++ -fsyntax-only %s -verify=cxx
 // RUN: %clang_cc1 -x c++ -fsyntax-only %s -pedantic -verify=cxx-pedantic
+// RUN: %clang_cc1 -x c++ -fsyntax-only %s -verify=cxx -fexperimental-new-constant-interpreter
+// RUN: %clang_cc1 -x c++ -fsyntax-only %s -pedantic -verify=cxx-pedantic -fexperimental-new-constant-interpreter
 
 // c-no-diagnostics
 // cxx-no-diagnostics