Preserve unknown STDC pragma through preprocessor

[steven_wu]

Summary

#pragma STDC FP_CONTRACT handler is only registered in parser so we
should keep the unknown STDC pragma through preprocessor and we also
should not emit warning for unknown STDC pragma during preprocessor.

rdar://problem/35724351

[efriedma]

If you move all the #pragma STDC handlers from the lexer to the parser, you might be able to avoid adding an explicit STDC handler in PrintPreprocessedOutput.cpp.

test/Preprocessor/pragma_unknown.c

43

Maybe add CHECK lines to make sure these come out correctly?

[steven_wu]

In D41780#968664, @efriedma wrote:

If you move all the #pragma STDC handlers from the lexer to the parser, you might be able to avoid adding an explicit STDC handler in PrintPreprocessedOutput.cpp.

If it is safe to do that, I can change it. I am not sure if the other STDC pragmas would affect preprocessor output in any other way (which seems not).

[efriedma]

Should be safe, I think; currently, FENV_ACCESS and CX_LIMITED_RANGE have no effect, and when we do start supporting them, we'll probably want to handle them in the parser, like we do for FP_CONTRACT.

[steven_wu]

Move STDC pragma handler to parser.

[efriedma]

LGTM

include/clang/Basic/DiagnosticLexKinds.td

 def warn_pragma_pop_macro_no_push : Warning<
    "pragma pop_macro could not pop '%0', no matching push_macro">,
   InGroup<IgnoredPragmas>;
 def warn_pragma_message : Warning<"%0">,
    InGroup<PoundPragmaMessage>, DefaultWarnNoWerror;
 def err_pragma_message : Error<"%0">;
 def warn_pragma_ignored : Warning<"unknown pragma ignored">,
    InGroup<UnknownPragmas>, DefaultIgnore;
-def ext_stdc_pragma_ignored : ExtWarn<"unknown pragma in STDC namespace">,
-   InGroup<UnknownPragmas>;
 def ext_on_off_switch_syntax :
    ExtWarn<"expected 'ON' or 'OFF' or 'DEFAULT' in pragma">,
    InGroup<UnknownPragmas>;
 def ext_pragma_syntax_eod :
    ExtWarn<"expected end of directive in pragma">,
    InGroup<UnknownPragmas>;
-def warn_stdc_fenv_access_not_supported :
-   Warning<"pragma STDC FENV_ACCESS ON is not supported, ignoring pragma">,
-   InGroup<UnknownPragmas>;
 def warn_pragma_diagnostic_invalid :
    ExtWarn<"pragma diagnostic expected 'error', 'warning', 'ignored', 'fatal',"
             " 'push', or 'pop'">,
    InGroup<UnknownPragmas>;
 def warn_pragma_diagnostic_cannot_pop :
    ExtWarn<"pragma diagnostic pop could not pop, no matching push">,
    InGroup<UnknownPragmas>;
 def warn_pragma_diagnostic_invalid_option :

include/clang/Basic/DiagnosticParseKinds.td

 def warn_pragma_init_seg_unsupported_target : Warning<
   "'#pragma init_seg' is only supported when targeting a "
   "Microsoft environment">,
   InGroup<IgnoredPragmas>;
 // - #pragma fp_contract
 def err_pragma_fp_contract_scope : Error<
   "'#pragma fp_contract' can only appear at file scope or at the start of a "
   "compound statement">; 
+// - #pragma stdc unknown
+def ext_stdc_pragma_ignored : ExtWarn<"unknown pragma in STDC namespace">,
+   InGroup<UnknownPragmas>;
+def warn_stdc_fenv_access_not_supported :
+   Warning<"pragma STDC FENV_ACCESS ON is not supported, ignoring pragma">,
+   InGroup<UnknownPragmas>;
 // - #pragma comment
 def err_pragma_comment_malformed : Error<
   "pragma comment requires parenthesized identifier and optional string">;
 def err_pragma_comment_unknown_kind : Error<"unknown kind of pragma comment">;
 // PS4 recognizes only #pragma comment(lib)
 def warn_pragma_comment_ignored : Warning<"'#pragma comment %0' ignored">,
   InGroup<IgnoredPragmas>;
 // - #pragma detect_mismatch

include/clang/Parse/Parser.h

class Parser : public CodeCompletionHandler {
   std::unique_ptr<PragmaHandler> MSRuntimeChecks;
   std::unique_ptr<PragmaHandler> MSIntrinsic;
   std::unique_ptr<PragmaHandler> CUDAForceHostDeviceHandler;
   std::unique_ptr<PragmaHandler> OptimizeHandler;
   std::unique_ptr<PragmaHandler> LoopHintHandler;
   std::unique_ptr<PragmaHandler> UnrollHintHandler;
   std::unique_ptr<PragmaHandler> NoUnrollHintHandler;
   std::unique_ptr<PragmaHandler> FPHandler;
+  std::unique_ptr<PragmaHandler> STDCFENVHandler;
+  std::unique_ptr<PragmaHandler> STDCCXLIMITHandler;
+  std::unique_ptr<PragmaHandler> STDCUnknownHandler;
   std::unique_ptr<PragmaHandler> AttributePragmaHandler;
 
   std::unique_ptr<CommentHandler> CommentSemaHandler;
 
   /// Whether the '>' token acts as an operator or not. This will be
   /// true except when we are parsing an expression within a C++
   /// template argument list, where the '>' closes the template
   /// argument list.

lib/Lex/Pragma.cpp

struct PragmaPopMacroHandler : public PragmaHandler {
   PragmaPopMacroHandler() : PragmaHandler("pop_macro") {}
 
   void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                     Token &PopMacroTok) override {
     PP.HandlePragmaPopMacro(PopMacroTok);
   }
 };
 
-// Pragma STDC implementations.
-
-/// PragmaSTDC_FENV_ACCESSHandler - "\#pragma STDC FENV_ACCESS ...".
-struct PragmaSTDC_FENV_ACCESSHandler : public PragmaHandler {
-  PragmaSTDC_FENV_ACCESSHandler() : PragmaHandler("FENV_ACCESS") {}
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &Tok) override {
-    tok::OnOffSwitch OOS;
-    if (PP.LexOnOffSwitch(OOS))
-     return;
-    if (OOS == tok::OOS_ON)
-      PP.Diag(Tok, diag::warn_stdc_fenv_access_not_supported);
-  }
-};
-
-/// PragmaSTDC_CX_LIMITED_RANGEHandler - "\#pragma STDC CX_LIMITED_RANGE ...".
-struct PragmaSTDC_CX_LIMITED_RANGEHandler : public PragmaHandler {
-  PragmaSTDC_CX_LIMITED_RANGEHandler() : PragmaHandler("CX_LIMITED_RANGE") {}
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &Tok) override {
-    tok::OnOffSwitch OOS;
-    PP.LexOnOffSwitch(OOS);
-  }
-};
-
-/// PragmaSTDC_UnknownHandler - "\#pragma STDC ...".
-struct PragmaSTDC_UnknownHandler : public PragmaHandler {
-  PragmaSTDC_UnknownHandler() = default;
-
-  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
-                    Token &UnknownTok) override {
-    // C99 6.10.6p2, unknown forms are not allowed.
-    PP.Diag(UnknownTok, diag::ext_stdc_pragma_ignored);
-  }
-};
-
 /// PragmaARCCFCodeAuditedHandler - 
 ///   \#pragma clang arc_cf_code_audited begin/end
 struct PragmaARCCFCodeAuditedHandler : public PragmaHandler {
   PragmaARCCFCodeAuditedHandler() : PragmaHandler("arc_cf_code_audited") {}
 
   void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                     Token &NameTok) override {
     SourceLocation Loc = NameTok.getLocation();
void Preprocessor::RegisterBuiltinPragmas() {
   auto *ModuleHandler = new PragmaNamespace("module");
   AddPragmaHandler("clang", ModuleHandler);
   ModuleHandler->AddPragma(new PragmaModuleImportHandler());
   ModuleHandler->AddPragma(new PragmaModuleBeginHandler());
   ModuleHandler->AddPragma(new PragmaModuleEndHandler());
   ModuleHandler->AddPragma(new PragmaModuleBuildHandler());
   ModuleHandler->AddPragma(new PragmaModuleLoadHandler());
 
-  AddPragmaHandler("STDC", new PragmaSTDC_FENV_ACCESSHandler());
-  AddPragmaHandler("STDC", new PragmaSTDC_CX_LIMITED_RANGEHandler());
-  AddPragmaHandler("STDC", new PragmaSTDC_UnknownHandler());
-
   // MS extensions.
   if (LangOpts.MicrosoftExt) {
     AddPragmaHandler(new PragmaWarningHandler());
     AddPragmaHandler(new PragmaIncludeAliasHandler());
     AddPragmaHandler(new PragmaRegionHandler("region"));
     AddPragmaHandler(new PragmaRegionHandler("endregion"));
   }
 
   // Pragmas added by plugins
   for (PragmaHandlerRegistry::iterator it = PragmaHandlerRegistry::begin(),
                                        ie = PragmaHandlerRegistry::end();
        it != ie; ++it) {
     AddPragmaHandler(it->instantiate().release());
   }
 }
 
 /// Ignore all pragmas, useful for modes such as -Eonly which would otherwise
 /// warn about those pragmas being unknown.
 void Preprocessor::IgnorePragmas() {
   AddPragmaHandler(new EmptyPragmaHandler());
   // Also ignore all pragmas in all namespaces created
   // in Preprocessor::RegisterBuiltinPragmas().
   AddPragmaHandler("GCC", new EmptyPragmaHandler());
   AddPragmaHandler("clang", new EmptyPragmaHandler());
-  if (PragmaHandler *NS = PragmaHandlers->FindHandler("STDC")) {
-    // Preprocessor::RegisterBuiltinPragmas() already registers
-    // PragmaSTDC_UnknownHandler as the empty handler, so remove it first,
-    // otherwise there will be an assert about a duplicate handler.
-    PragmaNamespace *STDCNamespace = NS->getIfNamespace();
-    assert(STDCNamespace &&
-           "Invalid namespace, registered as a regular pragma handler!");
-    if (PragmaHandler *Existing = STDCNamespace->FindHandler("", false)) {
-      RemovePragmaHandler("STDC", Existing);
-      delete Existing;
-    }
-  }
-  AddPragmaHandler("STDC", new EmptyPragmaHandler());
 }

lib/Parse/ParsePragma.cpp

 
 
 struct PragmaFPContractHandler : public PragmaHandler {
   PragmaFPContractHandler() : PragmaHandler("FP_CONTRACT") {}
   void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                     Token &FirstToken) override;
 };
 
+// Pragma STDC implementations.
+
+/// PragmaSTDC_FENV_ACCESSHandler - "\#pragma STDC FENV_ACCESS ...".
+struct PragmaSTDC_FENV_ACCESSHandler : public PragmaHandler {
+  PragmaSTDC_FENV_ACCESSHandler() : PragmaHandler("FENV_ACCESS") {}
+
+  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
+                    Token &Tok) override {
+    tok::OnOffSwitch OOS;
+    if (PP.LexOnOffSwitch(OOS))
+     return;
+    if (OOS == tok::OOS_ON)
+      PP.Diag(Tok, diag::warn_stdc_fenv_access_not_supported);
+  }
+};
+
+/// PragmaSTDC_CX_LIMITED_RANGEHandler - "\#pragma STDC CX_LIMITED_RANGE ...".
+struct PragmaSTDC_CX_LIMITED_RANGEHandler : public PragmaHandler {
+  PragmaSTDC_CX_LIMITED_RANGEHandler() : PragmaHandler("CX_LIMITED_RANGE") {}
+
+  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
+                    Token &Tok) override {
+    tok::OnOffSwitch OOS;
+    PP.LexOnOffSwitch(OOS);
+  }
+};
+
+/// PragmaSTDC_UnknownHandler - "\#pragma STDC ...".
+struct PragmaSTDC_UnknownHandler : public PragmaHandler {
+  PragmaSTDC_UnknownHandler() = default;
+
+  void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
+                    Token &UnknownTok) override {
+    // C99 6.10.6p2, unknown forms are not allowed.
+    PP.Diag(UnknownTok, diag::ext_stdc_pragma_ignored);
+  }
+};
+
 struct PragmaFPHandler : public PragmaHandler {
   PragmaFPHandler() : PragmaHandler("fp") {}
   void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
                     Token &FirstToken) override;
 };
 
 struct PragmaNoOpenMPHandler : public PragmaHandler {
   PragmaNoOpenMPHandler() : PragmaHandler("omp") { }
void Parser::initializePragmaHandlers() {
   PP.AddPragmaHandler(WeakHandler.get());
 
   RedefineExtnameHandler.reset(new PragmaRedefineExtnameHandler());
   PP.AddPragmaHandler(RedefineExtnameHandler.get());
 
   FPContractHandler.reset(new PragmaFPContractHandler());
   PP.AddPragmaHandler("STDC", FPContractHandler.get());
 
+  STDCFENVHandler.reset(new PragmaSTDC_FENV_ACCESSHandler());
+  PP.AddPragmaHandler("STDC", STDCFENVHandler.get());
+
+  STDCCXLIMITHandler.reset(new PragmaSTDC_CX_LIMITED_RANGEHandler());
+  PP.AddPragmaHandler("STDC", STDCCXLIMITHandler.get());
+
+  STDCUnknownHandler.reset(new PragmaSTDC_UnknownHandler());
+  PP.AddPragmaHandler("STDC", STDCUnknownHandler.get());
+
   PCSectionHandler.reset(new PragmaClangSectionHandler(Actions));
   PP.AddPragmaHandler("clang", PCSectionHandler.get());
 
   if (getLangOpts().OpenCL) {
     OpenCLExtensionHandler.reset(new PragmaOpenCLExtensionHandler());
     PP.AddPragmaHandler("OPENCL", OpenCLExtensionHandler.get());
 
     PP.AddPragmaHandler("OPENCL", FPContractHandler.get());
void Parser::resetPragmaHandlers() {
   if (getLangOpts().CUDA) {
     PP.RemovePragmaHandler("clang", CUDAForceHostDeviceHandler.get());
     CUDAForceHostDeviceHandler.reset();
   }
 
   PP.RemovePragmaHandler("STDC", FPContractHandler.get());
   FPContractHandler.reset();
 
+  PP.RemovePragmaHandler("STDC", STDCFENVHandler.get());
+  STDCFENVHandler.reset();
+
+  PP.RemovePragmaHandler("STDC", STDCCXLIMITHandler.get());
+  STDCCXLIMITHandler.reset();
+
+  PP.RemovePragmaHandler("STDC", STDCUnknownHandler.get());
+  STDCUnknownHandler.reset();
+
   PP.RemovePragmaHandler("clang", OptimizeHandler.get());
   OptimizeHandler.reset();
 
   PP.RemovePragmaHandler("clang", LoopHintHandler.get());
   LoopHintHandler.reset();
 
   PP.RemovePragmaHandler(UnrollHintHandler.get());
   UnrollHintHandler.reset();

test/Preprocessor/pragma_unknown.c

 // RUN: %clang_cc1 -fsyntax-only -Wunknown-pragmas -verify %s
-// RUN: %clang_cc1 -E %s | FileCheck --strict-whitespace %s
+// RUN: %clang_cc1 -E %s 2>&1 | FileCheck --strict-whitespace %s
 
 // GCC doesn't expand macro args for unrecognized pragmas.
 #define bar xX
 #pragma foo bar   // expected-warning {{unknown pragma ignored}}
+// CHECK-NOT: unknown pragma in STDC namespace
 // CHECK: {{^}}#pragma foo bar{{$}}
 
 #pragma STDC FP_CONTRACT ON
 #pragma STDC FP_CONTRACT OFF
 #pragma STDC FP_CONTRACT DEFAULT
 #pragma STDC FP_CONTRACT IN_BETWEEN  // expected-warning {{expected 'ON' or 'OFF' or 'DEFAULT' in pragma}}
+// CHECK: {{^}}#pragma STDC FP_CONTRACT ON{{$}}
+// CHECK: {{^}}#pragma STDC FP_CONTRACT OFF{{$}}
+// CHECK: {{^}}#pragma STDC FP_CONTRACT DEFAULT{{$}}
+// CHECK: {{^}}#pragma STDC FP_CONTRACT IN_BETWEEN{{$}}
 
 #pragma STDC FENV_ACCESS ON          // expected-warning {{pragma STDC FENV_ACCESS ON is not supported, ignoring pragma}}
 #pragma STDC FENV_ACCESS OFF
 #pragma STDC FENV_ACCESS DEFAULT
 #pragma STDC FENV_ACCESS IN_BETWEEN   // expected-warning {{expected 'ON' or 'OFF' or 'DEFAULT' in pragma}}
+// CHECK: {{^}}#pragma STDC FENV_ACCESS ON{{$}}
+// CHECK: {{^}}#pragma STDC FENV_ACCESS OFF{{$}}
+// CHECK: {{^}}#pragma STDC FENV_ACCESS DEFAULT{{$}}
+// CHECK: {{^}}#pragma STDC FENV_ACCESS IN_BETWEEN{{$}}
 
 #pragma STDC CX_LIMITED_RANGE ON
 #pragma STDC CX_LIMITED_RANGE OFF
 #pragma STDC CX_LIMITED_RANGE DEFAULT 
 #pragma STDC CX_LIMITED_RANGE IN_BETWEEN   // expected-warning {{expected 'ON' or 'OFF' or 'DEFAULT' in pragma}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE ON{{$}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE OFF{{$}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE DEFAULT{{$}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE IN_BETWEEN{{$}}
 
 #pragma STDC CX_LIMITED_RANGE    // expected-warning {{expected 'ON' or 'OFF' or 'DEFAULT' in pragma}}
 #pragma STDC CX_LIMITED_RANGE ON FULL POWER  // expected-warning {{expected end of directive in pragma}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE{{$}}
+// CHECK: {{^}}#pragma STDC CX_LIMITED_RANGE ON FULL POWER{{$}}
 
 #pragma STDC SO_GREAT  // expected-warning {{unknown pragma in STDC namespace}}
 #pragma STDC   // expected-warning {{unknown pragma in STDC namespace}}
-
+// CHECK: {{^}}#pragma STDC SO_GREAT{{$}}
+// CHECK: {{^}}#pragma STDC{{$}}