Add a callback for `__has_include` and use it for dependency scanning.

This adds a preprocessor callback for the `__has_include` and
`__has_include_next` directives.

Successful checking for the presence of a header should add it to the list of
header dependencies so this overrides the callback in the dependency scanner.

Patch by Pete Cooper with some additions by me.

rdar://problem/39545636

Differential Revision: https://reviews.llvm.org/D30882

llvm-svn: 342517

clang/include/clang/Lex/PPCallbacks.h

@@ -276,6 +276,12 @@ public:
                        SourceRange Range) {
   }
 
+  /// Hook called when a '__has_include' or '__has_include_next' directive is
+  /// read.
+  virtual void HasInclude(SourceLocation Loc, StringRef FileName, bool IsAngled,
+                          const FileEntry *File,
+                          SrcMgr::CharacteristicKind FileType) {}
+
   /// Hook called when a source range is skipped.
   /// \param Range The SourceRange that was skipped. The range begins at the
   /// \#if/\#else directive and ends after the \#endif/\#else directive.
@@ -443,6 +449,13 @@ public:
     Second->PragmaDiagnostic(Loc, Namespace, mapping, Str);
   }
 
+  void HasInclude(SourceLocation Loc, StringRef FileName, bool IsAngled,
+                  const FileEntry *File,
+                  SrcMgr::CharacteristicKind FileType) override {
+    First->HasInclude(Loc, FileName, IsAngled, File, FileType);
+    Second->HasInclude(Loc, FileName, IsAngled, File, FileType);
+  }
+
   void PragmaOpenCLExtension(SourceLocation NameLoc, const IdentifierInfo *Name,
                              SourceLocation StateLoc, unsigned State) override {
     First->PragmaOpenCLExtension(NameLoc, Name, StateLoc, State);

clang/lib/Frontend/DependencyFile.cpp

@@ -200,6 +200,10 @@ public:
                           const Module *Imported,
                           SrcMgr::CharacteristicKind FileType) override;
 
+  void HasInclude(SourceLocation Loc, StringRef SpelledFilename, bool IsAngled,
+                  const FileEntry *File,
+                  SrcMgr::CharacteristicKind FileType) override;
+
   void EndOfMainFile() override {
     OutputDependencyFile();
   }
@@ -328,6 +332,17 @@ void DFGImpl::InclusionDirective(SourceLocation HashLoc,
   }
 }
 
+void DFGImpl::HasInclude(SourceLocation Loc, StringRef SpelledFilename,
+                         bool IsAngled, const FileEntry *File,
+                         SrcMgr::CharacteristicKind FileType) {
+  if (!File)
+    return;
+  StringRef Filename = File->getName();
+  if (!FileMatchesDepCriteria(Filename.data(), FileType))
+    return;
+  AddFilename(llvm::sys::path::remove_leading_dotslash(Filename));
+}
+
 bool DFGImpl::AddFilename(StringRef Filename) {
   if (FilesSet.insert(Filename).second) {
     Files.push_back(Filename);

clang/lib/Lex/PPMacroExpansion.cpp

@@ -23,6 +23,7 @@
 #include "clang/Lex/CodeCompletionHandler.h"
 #include "clang/Lex/DirectoryLookup.h"
 #include "clang/Lex/ExternalPreprocessorSource.h"
+#include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/LexDiagnostic.h"
 #include "clang/Lex/MacroArgs.h"
 #include "clang/Lex/MacroInfo.h"
@@ -1242,6 +1243,13 @@ static bool EvaluateHasIncludeCommon(Token &Tok,
       PP.LookupFile(FilenameLoc, Filename, isAngled, LookupFrom, LookupFromFile,
                     CurDir, nullptr, nullptr, nullptr, nullptr);
 
+  if (PPCallbacks *Callbacks = PP.getPPCallbacks()) {
+    SrcMgr::CharacteristicKind FileType = SrcMgr::C_User;
+    if (File)
+      FileType = PP.getHeaderSearchInfo().getFileDirFlavor(File);
+    Callbacks->HasInclude(FilenameLoc, Filename, isAngled, File, FileType);
+  }
+
   // Get the result value.  A result of true means the file exists.
   return File != nullptr;
 }

clang/test/Frontend/dependency-gen-has-include.c

@@ -0,0 +1,40 @@
+// REQUIRES: shell
+
+// Basic test
+// RUN: rm -rf %t.dir
+// RUN: mkdir %t.dir
+// RUN: mkdir %t.dir/a
+// RUN: echo "#ifndef HEADER_A" > %t.dir/a/header.h
+// RUN: echo "#define HEADER_A" >> %t.dir/a/header.h
+// RUN: echo "#endif" >> %t.dir/a/header.h
+// RUN: mkdir %t.dir/system
+// RUN: echo "#define SYSTEM_HEADER" > %t.dir/system/system-header.h
+// RUN: mkdir %t.dir/next-a
+// RUN: echo "#if __has_include_next(<next-header.h>)" > %t.dir/next-a/next-header.h
+// RUN: echo "#endif" >> %t.dir/next-a/next-header.h
+// RUN: mkdir %t.dir/next-b
+// RUN: echo "#define NEXT_HEADER" > %t.dir/next-b/next-header.h
+
+// RUN: %clang -MD -MF %t.dir/file.deps %s -fsyntax-only -I %t.dir -isystem %t.dir/system -I %t.dir/next-a -I %t.dir/next-b
+// RUN: FileCheck -input-file=%t.dir/file.deps %s
+// CHECK: dependency-gen-has-include.o
+// CHECK: dependency-gen-has-include.c
+// CHECK: a/header.h
+// CHECK-NOT: missing/file.h
+// CHECK: system/system-header.h
+// CHECK: next-a/next-header.h
+// CHECK: next-b/next-header.h
+
+// Verify that we ignore system headers in user-only headers mode.
+// RUN: %clang -MMD -MF %t.dir/user-headers.deps %s -fsyntax-only -I %t.dir -isystem %t.dir/system -I %t.dir/next-a -I %t.dir/next-b
+// RUN: FileCheck -input-file=%t.dir/user-headers.deps --check-prefix CHECK-USER-HEADER %s
+// CHECK-USER-HEADER-NOT: system/system-header.h
+
+#if __has_include("a/header.h")
+#endif
+#if __has_include("missing/file.h")
+#endif
+#if __has_include(<system-header.h>)
+#endif
+
+#include <next-header.h>