[PATCH] D150875: Make dereferencing a void* a hard-error instead of warn-as-error

[Erich Keane via Phabricator via cfe-commits]

erichkeane created this revision.
erichkeane added reviewers: clang-vendors, clang-language-wg.
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erichkeane requested review of this revision.

Clang 16 changed to consider dereferencing a void* to be a
warning-as-error, plus made this an error in SFINAE contexts, since this
resulted in incorrect template instantiation.  When doing so, the Clang
16 documentation was updated to reflect that this was likely to change
again to a non-disablable error in the next version.

As there has been no response to changing from a warning to an error, I
believe this is a non-controversial change.

This patch changes this to be an Error, consistent with the standard and
other compilers.


https://reviews.llvm.org/D150875

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/disallow_void_deref.cpp


Index: clang/test/SemaCXX/disallow_void_deref.cpp
===================================================================
--- clang/test/SemaCXX/disallow_void_deref.cpp
+++ clang/test/SemaCXX/disallow_void_deref.cpp
@@ -1,8 +1,7 @@
-// RUN: %clang_cc1 -fsyntax-only -verify=enabled,sfinae -std=c++20 %s
-// RUN: %clang_cc1 -fsyntax-only -verify=sfinae -std=c++20 -Wno-void-ptr-dereference %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
 
 void f(void* p) {
-  (void)*p; // enabled-error{{ISO C++ does not allow indirection on operand of type 'void *'}}
+  (void)*p; // expected-error{{ISO C++ does not allow indirection on operand of type 'void *'}}
 }
 
 template<class T>
@@ -11,6 +10,6 @@
 };
 
 static_assert(deref<void*>);
-// sfinae-error at -1{{static assertion failed}}
-// sfinae-note at -2{{because 'void *' does not satisfy 'deref'}}
-// sfinae-note@#FAILED_REQ{{because '*t' would be invalid: ISO C++ does not allow indirection on operand of type 'void *'}}
+// expected-error at -1{{static assertion failed}}
+// expected-note at -2{{because 'void *' does not satisfy 'deref'}}
+// expected-note@#FAILED_REQ{{because '*t' would be invalid: ISO C++ does not allow indirection on operand of type 'void *'}}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -14957,7 +14957,7 @@
     //   be a pointer to an object type, or a pointer to a function type
     LangOptions LO = S.getLangOpts();
     if (LO.CPlusPlus)
-      S.Diag(OpLoc, diag::ext_typecheck_indirection_through_void_pointer_cpp)
+      S.Diag(OpLoc, diag::err_typecheck_indirection_through_void_pointer_cpp)
           << OpTy << Op->getSourceRange();
     else if (!(LO.C99 && IsAfterAmp) && !S.isUnevaluatedContext())
       S.Diag(OpLoc, diag::ext_typecheck_indirection_through_void_pointer)
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6981,9 +6981,8 @@
 def ext_typecheck_indirection_through_void_pointer : ExtWarn<
   "ISO C does not allow indirection on operand of type %0">,
   InGroup<VoidPointerDeref>;
-def ext_typecheck_indirection_through_void_pointer_cpp
-    : ExtWarn<"ISO C++ does not allow indirection on operand of type %0">,
-      InGroup<VoidPointerDeref>, DefaultError, SFINAEFailure;
+def err_typecheck_indirection_through_void_pointer_cpp
+    : Error<"ISO C++ does not allow indirection on operand of type %0">;
 def warn_indirection_through_null : Warning<
   "indirection of non-volatile null pointer will be deleted, not trap">,
   InGroup<NullDereference>;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -55,6 +55,8 @@
 -----------------------------------------
 - Clang won't search for coroutine_traits in std::experimental namespace any more.
   Clang will only search for std::coroutine_traits for coroutines then.
+- Clang no longer allows dereferencing of a ``void*`` as an extension. Clang 16
+  converted this to a warning-as-default-error as well as a SFINAE error.
 
 ABI Changes in This Version
 ---------------------------


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