[clang] 6685e56 - Disallow dereferencing of void* in C++.
Erich Keane via cfe-commits
cfe-commits at lists.llvm.org
Mon Oct 10 07:11:57 PDT 2022
Author: Erich Keane
Date: 2022-10-10T07:11:46-07:00
New Revision: 6685e56ceddf7c88eb3c39e838a8164941aade05
URL: https://github.com/llvm/llvm-project/commit/6685e56ceddf7c88eb3c39e838a8164941aade05
DIFF: https://github.com/llvm/llvm-project/commit/6685e56ceddf7c88eb3c39e838a8164941aade05.diff
LOG: Disallow dereferencing of void* in C++.
as Discussed:
https://discourse.llvm.org/t/rfc-can-we-stop-the-extension-to-allow-dereferencing-void-in-c/65708
There is no good reason to allow this when the other compilers all
reject this, and it messes with SFINAE/constraint checking.
Differential Revision: https://reviews.llvm.org/D135287
Added:
clang/test/SemaCXX/disallow_void_deref.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/DiagnosticGroups.td
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/Sema/SemaExpr.cpp
clang/test/CXX/temp/temp.decls/temp.class/temp.mem.func/p1inst.cpp
clang/test/SemaCXX/reinterpret-cast.cpp
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 513a5eda80801..16e6522a44273 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -117,6 +117,18 @@ code bases.
These errors also match MSVC's behavior.
+- Clang now diagnoses indirection of ``void *`` in C++ mode as a warning which
+ defaults to an error. This is compatible with ISO C++, GCC, ICC, and MSVC. This
+ is also now a SFINAE error so constraint checking and SFINAE checking can be
+ compatible with other compilers. It is expected that this will be upgraded to
+ an error-only diagnostic in the next Clang release.
+
+ .. code-block:: c++
+
+ void func(void *p) {
+ *p; // Now diagnosed as a warning-as-error.
+ }
+
What's New in Clang |release|?
==============================
Some of the major new features and improvements to Clang are listed
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index ff88c8acec4c1..cddb127cae58f 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -961,6 +961,7 @@ def PointerToEnumCast : DiagGroup<"pointer-to-enum-cast",
[VoidPointerToEnumCast]>;
def PointerToIntCast : DiagGroup<"pointer-to-int-cast",
[PointerToEnumCast, VoidPointerToIntCast]>;
+def VoidPointerDeref : DiagGroup<"void-ptr-dereference">;
def FUseLdPath : DiagGroup<"fuse-ld-path">;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 8a721d45e78f0..d6fbaed126d64 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6936,8 +6936,11 @@ def err_typecheck_unary_expr : Error<
def err_typecheck_indirection_requires_pointer : Error<
"indirection requires pointer operand (%0 invalid)">;
def ext_typecheck_indirection_through_void_pointer : ExtWarn<
- "ISO %select{C|C++}0 does not allow indirection on operand of type %1">,
- InGroup<DiagGroup<"void-ptr-dereference">>;
+ "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 warn_indirection_through_null : Warning<
"indirection of non-volatile null pointer will be deleted, not trap">,
InGroup<NullDereference>;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 6d28a44952318..474f86cffd169 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -14536,9 +14536,12 @@ static QualType CheckIndirectionOperand(Sema &S, Expr *Op, ExprValueKind &VK,
// [...] the expression to which [the unary * operator] is applied shall
// be a pointer to an object type, or a pointer to a function type
LangOptions LO = S.getLangOpts();
- if (LO.CPlusPlus || (!(LO.C99 && IsAfterAmp) && !S.isUnevaluatedContext()))
+ if (LO.CPlusPlus)
+ S.Diag(OpLoc, diag::ext_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)
- << LO.CPlusPlus << OpTy << Op->getSourceRange();
+ << OpTy << Op->getSourceRange();
}
// Dereferences are usually l-values...
diff --git a/clang/test/CXX/temp/temp.decls/temp.class/temp.mem.func/p1inst.cpp b/clang/test/CXX/temp/temp.decls/temp.class/temp.mem.func/p1inst.cpp
index eb11e3375e5f6..6d591457ae149 100644
--- a/clang/test/CXX/temp/temp.decls/temp.class/temp.mem.func/p1inst.cpp
+++ b/clang/test/CXX/temp/temp.decls/temp.class/temp.mem.func/p1inst.cpp
@@ -8,7 +8,7 @@ struct X0 {
template<typename T, typename U>
void X0<T, U>::f(T *t, const U &u) {
- *t = u; // expected-warning{{indirection on operand of type 'void *'}} expected-error{{not assignable}}
+ *t = u; // expected-error{{indirection on operand of type 'void *'}} expected-error{{not assignable}}
}
void test_f(X0<float, int> xfi, X0<void, int> xvi, float *fp, void *vp, int i) {
diff --git a/clang/test/SemaCXX/disallow_void_deref.cpp b/clang/test/SemaCXX/disallow_void_deref.cpp
new file mode 100644
index 0000000000000..2981e709525b2
--- /dev/null
+++ b/clang/test/SemaCXX/disallow_void_deref.cpp
@@ -0,0 +1,16 @@
+// 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
+
+void f(void* p) {
+ (void)*p; // enabled-error{{ISO C++ does not allow indirection on operand of type 'void *'}}
+}
+
+template<class T>
+concept deref = requires (T& t) {
+ { *t }; // #FAILED_REQ
+};
+
+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 *'}}
diff --git a/clang/test/SemaCXX/reinterpret-cast.cpp b/clang/test/SemaCXX/reinterpret-cast.cpp
index 1b84df12129c7..ee856485272b2 100644
--- a/clang/test/SemaCXX/reinterpret-cast.cpp
+++ b/clang/test/SemaCXX/reinterpret-cast.cpp
@@ -214,11 +214,11 @@ void dereference_reinterpret_cast() {
(void)*reinterpret_cast<float*>(v_ptr);
// Casting to void pointer
- (void)*reinterpret_cast<void*>(&a); // expected-warning {{ISO C++ does not allow}}
- (void)*reinterpret_cast<void*>(&b); // expected-warning {{ISO C++ does not allow}}
- (void)*reinterpret_cast<void*>(&l); // expected-warning {{ISO C++ does not allow}}
- (void)*reinterpret_cast<void*>(&d); // expected-warning {{ISO C++ does not allow}}
- (void)*reinterpret_cast<void*>(&f); // expected-warning {{ISO C++ does not allow}}
+ (void)*reinterpret_cast<void*>(&a); // expected-error {{ISO C++ does not allow}}
+ (void)*reinterpret_cast<void*>(&b); // expected-error {{ISO C++ does not allow}}
+ (void)*reinterpret_cast<void*>(&l); // expected-error {{ISO C++ does not allow}}
+ (void)*reinterpret_cast<void*>(&d); // expected-error {{ISO C++ does not allow}}
+ (void)*reinterpret_cast<void*>(&f); // expected-error {{ISO C++ does not allow}}
}
void reinterpret_cast_allowlist () {
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