Do not print certain warnings when input is a header.

[erikjv]

Summary

When generating pre-compiled headers, or when opening a header file with
libclang, suppress the warnings "#pragma once in main file" and
"#include_next in primary source file".

Fixes PR16686 and PR24390.

[mehdi_amini]

include/clang/Basic/SourceManager.h

660 ↗

(On Diff #44121)

Document?

764 ↗

(On Diff #44121)

Variable should start with a capital

include/clang/Frontend/FrontendOptions.h

91 ↗

(On Diff #44121)

Document

[erikjv]

ping?

[aaron.ballman]

include/clang/Basic/LangOptions.h

131

Should move the initializer to the constructor (not certain that MSVC 2013 supports this construct, but it's also more consistent).

[mehdi_amini]

include/clang/Basic/LangOptions.h

131

Interestingly I prefer to have them on the fields themselves (when writing new struct/classes), but I agree that consistency takes precedence when adding a field to an existing class.

include/clang/Basic/LangOptions.h

public:
   /// \brief Triples of the OpenMP targets that the host code codegen should
   /// take into account in order to generate accurate offloading descriptors.
   std::vector<llvm::Triple> OMPTargetTriples;
 
   /// \brief Name of the IR file that contains the result of the OpenMP target
   /// host code generation.
   std::string OMPHostIRFile;
 
+  /// \brief Indicates whether the front-end is explicitly told that the
+  /// input is a header file (i.e. -x c-header).
+  bool IsHeaderFile = false;
+
   LangOptions();
 
   // Define accessors/mutators for language options of enumeration type.
 #define LANGOPT(Name, Bits, Default, Description) 
 #define ENUM_LANGOPT(Name, Type, Bits, Default, Description) \
   Type get##Name() const { return static_cast<Type>(Name); } \
   void set##Name(Type Value) { Name = static_cast<unsigned>(Value); }  
 #include "clang/Basic/LangOptions.def"

lib/Frontend/CompilerInvocation.cpp

static bool parseTestModuleFileExtensionArg(StringRef Arg,
   if (Args[2].getAsInteger(10, MinorVersion)) return true;
   if (Args[3].getAsInteger(2, Hashed)) return true;
   if (Args.size() > 4)
     UserInfo = Args[4];
   return false;
 }
 
 static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
-                                   DiagnosticsEngine &Diags) {
+                                   DiagnosticsEngine &Diags,
+                                   bool &IsHeaderFile) {
   using namespace options;
   Opts.ProgramAction = frontend::ParseSyntaxOnly;
   if (const Arg *A = Args.getLastArg(OPT_Action_Group)) {
     switch (A->getOption().getID()) {
     default:
       llvm_unreachable("Invalid option in group!");
     case OPT_ast_list:
       Opts.ProgramAction = frontend::ASTDeclList; break;
DashX = llvm::StringSwitch<InputKind>(A->getValue())
       .Case("c++-header", IK_CXX)
       .Case("objective-c++-header", IK_ObjCXX)
       .Cases("ast", "pcm", IK_AST)
       .Case("ir", IK_LLVM_IR)
       .Default(IK_None);
     if (DashX == IK_None)
       Diags.Report(diag::err_drv_invalid_value)
         << A->getAsString(Args) << A->getValue();
+
+    IsHeaderFile = llvm::StringSwitch<bool>(A->getValue())
+        .Case("c-header", true)
+        .Case("cl-header", true)
+        .Case("objective-c-header", true)
+        .Case("c++-header", true)
+        .Case("objective-c++-header", true)
+        .Default(false);
   }
 
   // '-' is the default input if none is given.
   std::vector<std::string> Inputs = Args.getAllArgValues(OPT_INPUT);
   Opts.Inputs.clear();
   if (Inputs.empty())
     Inputs.push_back("-");
   for (unsigned i = 0, e = Inputs.size(); i != e; ++i) {
bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
   Success &= ParseAnalyzerArgs(*Res.getAnalyzerOpts(), Args, Diags);
   Success &= ParseMigratorArgs(Res.getMigratorOpts(), Args);
   ParseDependencyOutputArgs(Res.getDependencyOutputOpts(), Args);
   Success &= ParseDiagnosticArgs(Res.getDiagnosticOpts(), Args, &Diags,
                                  false /*DefaultDiagColor*/);
   ParseCommentArgs(LangOpts.CommentOpts, Args);
   ParseFileSystemArgs(Res.getFileSystemOpts(), Args);
   // FIXME: We shouldn't have to pass the DashX option around here
-  InputKind DashX = ParseFrontendArgs(Res.getFrontendOpts(), Args, Diags);
+  InputKind DashX = ParseFrontendArgs(Res.getFrontendOpts(), Args, Diags,
+                                      LangOpts.IsHeaderFile);
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
   Success &= ParseCodeGenArgs(Res.getCodeGenOpts(), Args, DashX, Diags,
                               Res.getTargetOpts());
   ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args);
   if (DashX == IK_AST || DashX == IK_LLVM_IR) {
     // ObjCAAutoRefCount and Sanitize LangOpts are used to setup the
     // PassManager in BackendUtil.cpp. They need to be initializd no matter
     // what the input type is.

lib/Lex/PPDirectives.cpp

void Preprocessor::HandleIncludeNextDirective(SourceLocation HashLoc,
                                               Token &IncludeNextTok) {
   Diag(IncludeNextTok, diag::ext_pp_include_next_directive);
 
   // #include_next is like #include, except that we start searching after
   // the current found directory.  If we can't do this, issue a
   // diagnostic.
   const DirectoryLookup *Lookup = CurDirLookup;
   const FileEntry *LookupFromFile = nullptr;
-  if (isInPrimaryFile()) {
+  if (isInPrimaryFile() && LangOpts.IsHeaderFile) {
+    // If the main file is a header, then it's either for PCH/AST generation,
+    // or libclang opened it. Either way, handle it as a normal include below.
+  } else if (isInPrimaryFile()) {
     Lookup = nullptr;
     Diag(IncludeNextTok, diag::pp_include_next_in_primary);
   } else if (CurSubmodule) {
     // Start looking up in the directory *after* the one in which the current
     // file would be found, if any.
     assert(CurPPLexer && "#include_next directive in macro?");
     LookupFromFile = CurPPLexer->getFileEntry();
     Lookup = nullptr;

lib/Lex/PPMacroExpansion.cpp

static bool EvaluateHasIncludeNext(Token &Tok,
                                    IdentifierInfo *II, Preprocessor &PP) {
   // __has_include_next is like __has_include, except that we start
   // searching after the current found directory.  If we can't do this,
   // issue a diagnostic.
   // FIXME: Factor out duplication with 
   // Preprocessor::HandleIncludeNextDirective.
   const DirectoryLookup *Lookup = PP.GetCurDirLookup();
   const FileEntry *LookupFromFile = nullptr;
-  if (PP.isInPrimaryFile()) {
+  if (PP.isInPrimaryFile() && PP.getLangOpts().IsHeaderFile) {
+    // If the main file is a header, then it's either for PCH/AST generation,
+    // or libclang opened it. Either way, handle it as a normal include below.
+  } else if (PP.isInPrimaryFile()) {
     Lookup = nullptr;
     PP.Diag(Tok, diag::pp_include_next_in_primary);
   } else if (PP.getCurrentSubmodule()) {
     // Start looking up in the directory *after* the one in which the current
     // file would be found, if any.
     assert(PP.getCurrentLexer() && "#include_next directive in macro?");
     LookupFromFile = PP.getCurrentLexer()->getFileEntry();
     Lookup = nullptr;

lib/Lex/Pragma.cpp

void Preprocessor::HandleMicrosoft__pragma(Token &Tok) {
 
   // Finally, return whatever came after the pragma directive.
   return Lex(Tok);
 }
 
 /// HandlePragmaOnce - Handle \#pragma once.  OnceTok is the 'once'.
 ///
 void Preprocessor::HandlePragmaOnce(Token &OnceTok) {
-  if (isInPrimaryFile()) {
+  // If the main file is a header, then it's either for PCH/AST generation,
+  // or libclang opened it. Allow #pragma once either way.
+  if (isInPrimaryFile() && !getLangOpts().IsHeaderFile) {
     Diag(OnceTok, diag::pp_pragma_once_in_main_file);
     return;
   }
 
   // Get the current file lexer we're looking at.  Ignore _Pragma 'files' etc.
   // Mark the file as a once-only file now.
   HeaderInfo.MarkFileIncludeOnce(getCurrentFileLexer()->getFileEntry());
 }

test/Preprocessor/header_is_main_file.c

+// RUN: %clang_cc1 -x c-header -ffreestanding -Eonly -verify %s
+// expected-no-diagnostics
+
+#pragma once
+#include_next "stdint.h"
+#if !__has_include_next("stdint.h")
+#error "__has_include_next failed"
+#endif