MaxMood96 · pull · Oct 17, 2021 · Oct 17, 2021 · Oct 17, 2021 · Sep 27, 2021
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -110,6 +110,13 @@ Attribute Changes in Clang
   attribute is handled instead, e.g. in ``handleDeclAttribute``.
   (This was changed in order to better support attributes in code completion).
 
+- __has_cpp_attribute, __has_c_attribute, __has_attribute, and __has_declspec
+  will now macro expand their argument. This causes a change in behavior for
+  code using ``__has_cpp_attribute(__clang__::attr)`` (and same for
+  ``__has_c_attribute``) where it would previously expand to ``0`` for all
+  attributes, but will now issue an error due to the expansion of the
+  predefined ``__clang__`` macro.
+
 Windows Support
 ---------------
 
@@ -122,6 +129,9 @@ Windows Support
 C Language Changes in Clang
 ---------------------------
 
+- The value of ``__STDC_VERSION__`` has been bumped to ``202000L`` when passing
+  ``-std=c2x`` so that it can be distinguished from C17 mode. This value is
+  expected to change again when C23 is published.
 - Wide multi-characters literals such as ``L'ab'`` that would previously be interpreted as ``L'b'``
   are now ill-formed in all language modes. The motivation for this change is outlined in
   `P2362 <wg21.link/P2362>`_.

diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -212,7 +212,7 @@ StringRef riscv::getRISCVABI(const ArgList &Args, const llvm::Triple &Triple) {
         return "lp64d";
       return "lp64";
     }
-    llvm_unreachable();
+    llvm_unreachable("unhandled XLen");
   }
 
   // 3. Choose a default based on the triple

diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -371,7 +371,10 @@ static void InitializeStandardPredefinedMacros(const TargetInfo &TI,
   //      value is, are implementation-defined.
   // (Removed in C++20.)
   if (!LangOpts.CPlusPlus) {
-    if (LangOpts.C17)
+    // FIXME: Use correct value for C23.
+    if (LangOpts.C2x)
+      Builder.defineMacro("__STDC_VERSION__", "202000L");
+    else if (LangOpts.C17)
       Builder.defineMacro("__STDC_VERSION__", "201710L");
     else if (LangOpts.C11)
       Builder.defineMacro("__STDC_VERSION__", "201112L");

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1293,7 +1293,7 @@ static bool EvaluateHasIncludeNext(Token &Tok,
 /// integer values.
 static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS,
                                             Token &Tok, IdentifierInfo *II,
-                                            Preprocessor &PP,
+                                            Preprocessor &PP, bool ExpandArgs,
                                             llvm::function_ref<
                                               int(Token &Tok,
                                                   bool &HasLexedNextTok)> Op) {
@@ -1319,7 +1319,10 @@ static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS,
   bool SuppressDiagnostic = false;
   while (true) {
     // Parse next token.
-    PP.LexUnexpandedToken(Tok);
+    if (ExpandArgs)
+      PP.Lex(Tok);
+    else
+      PP.LexUnexpandedToken(Tok);
 
 already_lexed:
     switch (Tok.getKind()) {
@@ -1609,21 +1612,21 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     OS << CounterValue++;
     Tok.setKind(tok::numeric_constant);
   } else if (II == Ident__has_feature) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
         return II && HasFeature(*this, II->getName());
       });
   } else if (II == Ident__has_extension) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
         return II && HasExtension(*this, II->getName());
       });
   } else if (II == Ident__has_builtin) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
@@ -1675,20 +1678,20 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
         }
       });
   } else if (II == Ident__is_identifier) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [](Token &Tok, bool &HasLexedNextToken) -> int {
         return Tok.is(tok::identifier);
       });
   } else if (II == Ident__has_attribute) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
         return II ? hasAttribute(AttrSyntax::GNU, nullptr, II,
                                  getTargetInfo(), getLangOpts()) : 0;
       });
   } else if (II == Ident__has_declspec) {
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                            diag::err_feature_check_malformed);
@@ -1704,8 +1707,8 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
   } else if (II == Ident__has_cpp_attribute ||
              II == Ident__has_c_attribute) {
     bool IsCXX = II == Ident__has_cpp_attribute;
-    EvaluateFeatureLikeBuiltinMacro(
-        OS, Tok, II, *this, [&](Token &Tok, bool &HasLexedNextToken) -> int {
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, true,
+        [&](Token &Tok, bool &HasLexedNextToken) -> int {
           IdentifierInfo *ScopeII = nullptr;
           IdentifierInfo *II = ExpectFeatureIdentifierInfo(
               Tok, *this, diag::err_feature_check_malformed);
@@ -1719,7 +1722,8 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
             HasLexedNextToken = true;
           else {
             ScopeII = II;
-            LexUnexpandedToken(Tok);
+            // Lex an expanded token for the attribute name.
+            Lex(Tok);
             II = ExpectFeatureIdentifierInfo(Tok, *this,
                                              diag::err_feature_check_malformed);
           }
@@ -1746,7 +1750,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     Tok.setKind(tok::numeric_constant);
   } else if (II == Ident__has_warning) {
     // The argument should be a parenthesized string literal.
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         std::string WarningName;
         SourceLocation StrStartLoc = Tok.getLocation();
@@ -1777,7 +1781,7 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     // The argument to this builtin should be an identifier. The
     // builtin evaluates to 1 when that identifier names the module we are
     // currently building.
-    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this,
+    EvaluateFeatureLikeBuiltinMacro(OS, Tok, II, *this, false,
       [this](Token &Tok, bool &HasLexedNextToken) -> int {
         IdentifierInfo *II = ExpectFeatureIdentifierInfo(Tok, *this,
                                        diag::err_expected_id_building_module);
@@ -1837,28 +1841,32 @@ void Preprocessor::ExpandBuiltinMacro(Token &Tok) {
     return;
   } else if (II == Ident__is_target_arch) {
     EvaluateFeatureLikeBuiltinMacro(
-        OS, Tok, II, *this, [this](Token &Tok, bool &HasLexedNextToken) -> int {
+        OS, Tok, II, *this, false,
+        [this](Token &Tok, bool &HasLexedNextToken) -> int {
           IdentifierInfo *II = ExpectFeatureIdentifierInfo(
               Tok, *this, diag::err_feature_check_malformed);
           return II && isTargetArch(getTargetInfo(), II);
         });
   } else if (II == Ident__is_target_vendor) {
     EvaluateFeatureLikeBuiltinMacro(
-        OS, Tok, II, *this, [this](Token &Tok, bool &HasLexedNextToken) -> int {
+        OS, Tok, II, *this, false,
+        [this](Token &Tok, bool &HasLexedNextToken) -> int {
           IdentifierInfo *II = ExpectFeatureIdentifierInfo(
               Tok, *this, diag::err_feature_check_malformed);
           return II && isTargetVendor(getTargetInfo(), II);
         });
   } else if (II == Ident__is_target_os) {
     EvaluateFeatureLikeBuiltinMacro(
-        OS, Tok, II, *this, [this](Token &Tok, bool &HasLexedNextToken) -> int {
+        OS, Tok, II, *this, false,
+        [this](Token &Tok, bool &HasLexedNextToken) -> int {
           IdentifierInfo *II = ExpectFeatureIdentifierInfo(
               Tok, *this, diag::err_feature_check_malformed);
           return II && isTargetOS(getTargetInfo(), II);
         });
   } else if (II == Ident__is_target_environment) {
     EvaluateFeatureLikeBuiltinMacro(
-        OS, Tok, II, *this, [this](Token &Tok, bool &HasLexedNextToken) -> int {
+        OS, Tok, II, *this, false,
+        [this](Token &Tok, bool &HasLexedNextToken) -> int {
           IdentifierInfo *II = ExpectFeatureIdentifierInfo(
               Tok, *this, diag::err_feature_check_malformed);
           return II && isTargetEnvironment(getTargetInfo(), II);

diff --git a/clang/test/Preprocessor/c2x.c b/clang/test/Preprocessor/c2x.c
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c2x %s
+// expected-no-diagnostics
+
+// FIXME: Test the correct value once C23 ships.
+_Static_assert(__STDC_VERSION__ > 201710L, "Incorrect __STDC_VERSION__");
diff --git a/clang/test/Preprocessor/has_attribute.c b/clang/test/Preprocessor/has_attribute.c
@@ -56,3 +56,11 @@ int has_no_volatile_attribute();
 
 #if __has_cpp_attribute(selectany) // expected-error {{function-like macro '__has_cpp_attribute' is not defined}}
 #endif
+
+// Test that macro expansion of the builtin argument works.
+#define F fallthrough
+
+#if __has_attribute(F)
+int has_fallthrough;
+#endif
+// CHECK: int has_fallthrough;
diff --git a/clang/test/Preprocessor/has_attribute.cpp b/clang/test/Preprocessor/has_attribute.cpp
@@ -18,16 +18,6 @@ CXX11(clang::__fallthrough__)
 // CHECK: __gsl__::suppress: 0
 CXX11(__gsl__::suppress)
 
-// We do somewhat support the __clang__ vendor namespace, but it is a
-// predefined macro and thus we encourage users to use _Clang instead.
-// Because of this, we do not support __has_cpp_attribute for that
-// vendor namespace.
-//
-// Note, we can't use CXX11 here because it will expand __clang__ to 1
-// too early.
-// CHECK: 1::fallthrough: 0
-__clang__::fallthrough: __has_cpp_attribute(__clang__::fallthrough)
-
 // CHECK: _Clang::fallthrough: 201603L
 CXX11(_Clang::fallthrough)
 
@@ -70,6 +60,50 @@ CXX11(unlikely)
 // CHECK: noreturn: 200809L
 // CHECK: unlikely: 201803L
 
+namespace PR48462 {
+// Test that macro expansion of the builtin argument works.
+#define C clang
+#define F fallthrough
+#define CF clang::fallthrough
+
+#if __has_cpp_attribute(F)
+int has_fallthrough;
+#endif
+// CHECK: int has_fallthrough;
+
+#if __has_cpp_attribute(C::F)
+int has_clang_falthrough_1;
+#endif
+// CHECK: int has_clang_falthrough_1;
+
+#if __has_cpp_attribute(clang::F)
+int has_clang_falthrough_2;
+#endif
+// CHECK: int has_clang_falthrough_2;
+
+#if __has_cpp_attribute(C::fallthrough)
+int has_clang_falthrough_3;
+#endif
+// CHECK: int has_clang_falthrough_3;
+
+#if __has_cpp_attribute(CF)
+int has_clang_falthrough_4;
+#endif
+// CHECK: int has_clang_falthrough_4;
+
+#define FUNCLIKE1(x) clang::x
+#if __has_cpp_attribute(FUNCLIKE1(fallthrough))
+int funclike_1;
+#endif
+// CHECK: int funclike_1;
+
+#define FUNCLIKE2(x) _Clang::x
+#if __has_cpp_attribute(FUNCLIKE2(fallthrough))
+int funclike_2;
+#endif
+// CHECK: int funclike_2;
+}
+
 // Test for Microsoft __declspec attributes
 
 #define DECLSPEC(x) x: __has_declspec_attribute(x)
@@ -81,3 +115,13 @@ DECLSPEC(__uuid__)
 
 // CHECK: fallthrough: 0
 DECLSPEC(fallthrough)
+
+namespace PR48462 {
+// Test that macro expansion of the builtin argument works.
+#define U uuid
+
+#if __has_declspec_attribute(U)
+int has_uuid;
+#endif
+// CHECK: int has_uuid;
+}
diff --git a/clang/test/Preprocessor/has_attribute_errors.cpp b/clang/test/Preprocessor/has_attribute_errors.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple i386-unknown-unknown -Eonly -verify %s
+
+// We warn users if they write an attribute like
+// [[__clang__::fallthrough]] because __clang__ is a macro that expands to 1.
+// Instead, we suggest users use [[_Clang::fallthrough]] in this situation.
+// However, because __has_cpp_attribute (and __has_c_attribute) require
+// expanding their argument tokens, __clang__ expands to 1 in the feature test
+// macro as well. We don't currently give users a kind warning in this case,
+// but we previously did not expand macros and so this would return 0. Now that
+// we properly expand macros, users will now get an error about using incorrect
+// syntax.
+
+__has_cpp_attribute(__clang__::fallthrough) // expected-error {{missing ')' after <numeric_constant>}} \
+                                            // expected-note {{to match this '('}} \
+                                            // expected-error {{builtin feature check macro requires a parenthesized identifier}}
+
diff --git a/clang/test/Preprocessor/has_c_attribute.c b/clang/test/Preprocessor/has_c_attribute.c
@@ -33,12 +33,45 @@ C2x(__gnu__::warn_unused_result)
 // CHECK: gnu::__warn_unused_result__: 201904L
 C2x(gnu::__warn_unused_result__)
 
-// We do somewhat support the __clang__ vendor namespace, but it is a
-// predefined macro and thus we encourage users to use _Clang instead.
-// Because of this, we do not support __has_c_attribute for that
-// vendor namespace.
-//
-// Note, we can't use C2x here because it will expand __clang__ to 1
-// too early.
-// CHECK: 1::fallthrough: 0
-__clang__::fallthrough: __has_c_attribute(__clang__::fallthrough)
+// Test that macro expansion of the builtin argument works.
+#define C clang
+#define L likely
+#define CL clang::likely
+#define N nodiscard
+
+#if __has_c_attribute(N)
+int has_nodiscard;
+#endif
+// CHECK: int has_nodiscard;
+
+#if __has_c_attribute(C::L)
+int has_clang_likely_1;
+#endif
+// CHECK: int has_clang_likely_1;
+
+#if __has_c_attribute(clang::L)
+int has_clang_likely_2;
+#endif
+// CHECK: int has_clang_likely_2;
+
+#if __has_c_attribute(C::likely)
+int has_clang_likely_3;
+#endif
+// CHECK: int has_clang_likely_3;
+
+#if __has_c_attribute(CL)
+int has_clang_likely_4;
+#endif
+// CHECK: int has_clang_likely_4;
+
+#define FUNCLIKE1(x) clang::x
+#if __has_c_attribute(FUNCLIKE1(likely))
+int funclike_1;
+#endif
+// CHECK: int funclike_1;
+
+#define FUNCLIKE2(x) _Clang::x
+#if __has_c_attribute(FUNCLIKE2(likely))
+int funclike_2;
+#endif
+// CHECK: int funclike_2;