Implement P1301R4, which allows specifying an optional message on the [[nodiscard]] attribute.
This also bumps the attribute feature test value and introduces the notion of a C++2a extension warning.
llvm-svn: 366626
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 5f0b369..d800f79 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -2841,14 +2841,30 @@
return;
}
- // If this is spelled as the standard C++17 attribute, but not in C++17, warn
- // about using it as an extension.
- if (!S.getLangOpts().CPlusPlus17 && AL.isCXX11Attribute() &&
- !AL.getScopeName())
- S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;
+ StringRef Str;
+ if ((AL.isCXX11Attribute() || AL.isC2xAttribute()) && !AL.getScopeName()) {
+ // If this is spelled as the standard C++17 attribute, but not in C++17,
+ // warn about using it as an extension. If there are attribute arguments,
+ // then claim it's a C++2a extension instead.
+ // FIXME: If WG14 does not seem likely to adopt the same feature, add an
+ // extension warning for C2x mode.
+ const LangOptions &LO = S.getLangOpts();
+ if (AL.getNumArgs() == 1) {
+ if (LO.CPlusPlus && !LO.CPlusPlus2a)
+ S.Diag(AL.getLoc(), diag::ext_cxx2a_attr) << AL;
+
+ // Since this this is spelled [[nodiscard]], get the optional string
+ // literal. If in C++ mode, but not in C++2a mode, diagnose as an
+ // extension.
+ // FIXME: C2x should support this feature as well, even as an extension.
+ if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, nullptr))
+ return;
+ } else if (LO.CPlusPlus && !LO.CPlusPlus17)
+ S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;
+ }
D->addAttr(::new (S.Context)
- WarnUnusedResultAttr(AL.getRange(), S.Context,
+ WarnUnusedResultAttr(AL.getRange(), S.Context, Str,
AL.getAttributeSpellingListIndex()));
}