[clang] [Clang] Fix __has_cpp_attribute and C++11 attributes with arguments in C++03 (PR #83065)

[Nikolas Klauser via cfe-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/83065


The values for `__has_cpp_attribute` don't have to be guarded behind `LangOpts.CPlusPlus` because `__has_cpp_attribute` isn't available if Clang isn't in a C++ mode.

Fixes #82995



>From b64d25b222b4c8c4839eb2e77f72c77596f133f2 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Mon, 26 Feb 2024 22:39:05 +0100
Subject: [PATCH] [Clang] Fix __has_cpp_attribute and C++11 attributes with
 arguments in C++03

---
 clang/test/SemaCXX/cxx03-cxx11-attr.cpp   |  9 +++++++++
 clang/utils/TableGen/ClangAttrEmitter.cpp | 12 +-----------
 2 files changed, 10 insertions(+), 11 deletions(-)
 create mode 100644 clang/test/SemaCXX/cxx03-cxx11-attr.cpp

diff --git a/clang/test/SemaCXX/cxx03-cxx11-attr.cpp b/clang/test/SemaCXX/cxx03-cxx11-attr.cpp
new file mode 100644
index 00000000000000..5a273c8fe2534a
--- /dev/null
+++ b/clang/test/SemaCXX/cxx03-cxx11-attr.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -std=c++03 -fsyntax-only %s
+
+// Ensure that __has_cpp_attribute and argument parsing work in C++03
+
+#if !__has_cpp_attribute(nodiscard)
+#  error
+#endif
+
+[[gnu::assume_aligned(4)]] void* g() { return __nullptr; }
diff --git a/clang/utils/TableGen/ClangAttrEmitter.cpp b/clang/utils/TableGen/ClangAttrEmitter.cpp
index 935b9846990ee5..eb5c34d15693d7 100644
--- a/clang/utils/TableGen/ClangAttrEmitter.cpp
+++ b/clang/utils/TableGen/ClangAttrEmitter.cpp
@@ -3576,10 +3576,6 @@ static void GenerateHasAttrSpellingStringSwitch(
       const Record *R = Attr->getValueAsDef("Target");
       std::vector<StringRef> Arches = R->getValueAsListOfStrings("Arches");
       GenerateTargetSpecificAttrChecks(R, Arches, Test, nullptr);
-
-      // If this is the C++11 variety, also add in the LangOpts test.
-      if (Variety == "CXX11")
-        Test += " && LangOpts.CPlusPlus11";
     } else if (!Attr->getValueAsListOfDefs("TargetSpecificSpellings").empty()) {
       // Add target checks if this spelling is target-specific.
       const std::vector<Record *> TargetSpellings =
@@ -3597,13 +3593,7 @@ static void GenerateHasAttrSpellingStringSwitch(
           }
         }
       }
-
-      if (Variety == "CXX11")
-        Test += " && LangOpts.CPlusPlus11";
-    } else if (Variety == "CXX11")
-      // C++11 mode should be checked against LangOpts, which is presumed to be
-      // present in the caller.
-      Test = "LangOpts.CPlusPlus11";
+    }
 
     std::string TestStr = !Test.empty()
                               ? Test + " ? " + llvm::itostr(Version) + " : 0"