[PATCH] D38205: [Sema] Warn on attribute nothrow conflicting with language specifiers

[Erich Keane via Phabricator via cfe-commits]

erichkeane updated this revision to Diff 116892.
erichkeane marked 2 inline comments as done.
erichkeane added a comment.

changes that were suggested by @aaron.ballman

It DOES warn on the template correctly, however I'm not thrilled that it misses the 'warning' info.  Any idea how I can get that information to give that 'note'?  I'd like an "in instantiation of template ..." type note.


https://reviews.llvm.org/D38205

Files:
  include/clang/Basic/DiagnosticSemaKinds.td
  lib/Sema/SemaDeclAttr.cpp
  test/SemaCXX/warn-conflicting-nothrow-attr-exception-spec.cpp


Index: test/SemaCXX/warn-conflicting-nothrow-attr-exception-spec.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/warn-conflicting-nothrow-attr-exception-spec.cpp
@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 %s -fcxx-exceptions -fsyntax-only -Wexceptions -verify -std=c++14
+
+struct S {
+  //expected-warning at +2 {{Attribute nothrow ignored due to conflicting exception specification}}
+  //expected-note at +1 {{exception specification declared here}}
+  __attribute__((nothrow)) S() noexcept(true);
+  //expected-warning at +2 {{Attribute nothrow ignored due to conflicting exception specification}}
+  //expected-note at +1 {{exception specification declared here}}
+  __attribute__((nothrow)) void Func1() noexcept(false);
+  __attribute__((nothrow)) void Func3() noexcept;
+};
+
+void throwing() noexcept(false);
+void non_throwing(bool b = true) noexcept;
+
+template <typename Fn>
+struct T {
+    __attribute__((nothrow)) void f(Fn) noexcept(Fn());
+};
+
+//expected-warning at -3 {{Attribute nothrow ignored due to conflicting exception specification}}
+//expected-note at -4 {{exception specification declared here}}
+template struct T<decltype(throwing)>;
+template struct T<decltype(non_throwing)>;
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -1985,6 +1985,25 @@
       attr.getRange(), S.Context, attr.getAttributeSpellingListIndex()));
 }
 
+static void handleNoThrowAttr(Sema &S, Decl *D, const AttributeList &Attrs) {
+  assert(isa<FunctionDecl>(D) && "attribute nothrow only valid on functions");
+
+  auto *FD = cast<FunctionDecl>(D);
+  const auto *FPT = FD->getType()->getAs<FunctionProtoType>();
+
+  if (FPT && FPT->hasExceptionSpec() &&
+      FPT->getExceptionSpecType() != EST_BasicNoexcept) {
+    S.Diag(Attrs.getLoc(),
+           diag::warn_nothrow_attr_disagrees_with_exception_specification);
+    S.Diag(FD->getExceptionSpecSourceRange().getBegin(),
+           diag::note_previous_decl)
+        << "exception specification";
+  }
+
+  D->addAttr(::new (S.Context) NoThrowAttr(
+      Attrs.getRange(), S.Context, Attrs.getAttributeSpellingListIndex()));
+}
+
 static void handleNoCallerSavedRegsAttr(Sema &S, Decl *D,
                                         const AttributeList &Attr) {
   if (S.CheckNoCallerSavedRegsAttr(Attr))
@@ -6211,7 +6230,7 @@
     handleNoReturnAttr(S, D, Attr);
     break;
   case AttributeList::AT_NoThrow:
-    handleSimpleAttribute<NoThrowAttr>(S, D, Attr);
+    handleNoThrowAttr(S, D, Attr);
     break;
   case AttributeList::AT_CUDAShared:
     handleSharedAttr(S, D, Attr);
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -1407,6 +1407,10 @@
   "argument to noexcept specifier must be a constant expression">;
 def err_exception_spec_not_parsed : Error<
   "exception specification is not available until end of class definition">;
+def warn_nothrow_attr_disagrees_with_exception_specification
+    : ExtWarn<"Attribute nothrow ignored due to conflicting exception "
+              "specification">,
+      InGroup<IgnoredAttributes>;
 
 // C++ access checking
 def err_class_redeclared_with_different_access : Error<


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