[clang] Make sure argument expansion locations are correct in presence of predefined buffer

Summary:
Macro argument expansion logic relies on skipping file IDs that created
as a result of an include. Unfortunately it fails to do that for
predefined buffer since it doesn't have a valid insertion location.

As a result of that any file ID created for an include inside the
predefined buffers breaks the traversal logic in
SourceManager::computeMacroArgsCache.

To fix this issue we first record number of created FIDs for predefined
buffer, and then skip them explicitly in source manager.

Another solution would be to just give predefined buffers a valid source
location, but it is unclear where that should be..

Reviewers: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78649

clang/lib/Basic/SourceManager.cpp

@@ -1800,15 +1800,23 @@ void SourceManager::computeMacroArgsCache(MacroArgsMap &MacroArgsCache,
       return;
     if (Entry.isFile()) {
       SourceLocation IncludeLoc = Entry.getFile().getIncludeLoc();
-      if (IncludeLoc.isInvalid())
-        continue;
-      if (!isInFileID(IncludeLoc, FID))
-        return; // No more files/macros that may be "contained" in this file.
-
-      // Skip the files/macros of the #include'd file, we only care about macros
-      // that lexed macro arguments from our file.
+      bool IncludedInFID =
+          (IncludeLoc.isValid() && isInFileID(IncludeLoc, FID)) ||
+          // Predefined header doesn't have a valid include location in main
+          // file, but any files created by it should still be skipped when
+          // computing macro args expanded in the main file.
+          (FID == MainFileID && Entry.getFile().Filename == "<built-in>");
+      if (IncludedInFID) {
+        // Skip the files/macros of the #include'd file, we only care about
+        // macros that lexed macro arguments from our file.
         if (Entry.getFile().NumCreatedFIDs)
-        ID += Entry.getFile().NumCreatedFIDs - 1/*because of next ++ID*/;
+          ID += Entry.getFile().NumCreatedFIDs - 1 /*because of next ++ID*/;
+        continue;
+      } else if (IncludeLoc.isValid()) {
+        // If file was included but not from FID, there is no more files/macros
+        // that may be "contained" in this file.
+        return;
+      }
       continue;
     }
 

clang/lib/Lex/PPLexerChange.cpp

@@ -415,7 +415,10 @@ bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
     }
 
     if (!isEndOfMacro && CurPPLexer &&
-        SourceMgr.getIncludeLoc(CurPPLexer->getFileID()).isValid()) {
+        (SourceMgr.getIncludeLoc(CurPPLexer->getFileID()).isValid() ||
+         // Predefines file doesn't have a valid include location.
+         (PredefinesFileID.isValid() &&
+          CurPPLexer->getFileID() == PredefinesFileID))) {
       // Notify SourceManager to record the number of FileIDs that were created
       // during lexing of the #include'd file.
       unsigned NumFIDs =

clang/unittests/Basic/SourceManagerTest.cpp

@@ -294,10 +294,16 @@ TEST_F(SourceManagerTest, getMacroArgExpandedLocation) {
   TrivialModuleLoader ModLoader;
   HeaderSearch HeaderInfo(std::make_shared<HeaderSearchOptions>(), SourceMgr,
                           Diags, LangOpts, &*Target);
+
   Preprocessor PP(std::make_shared<PreprocessorOptions>(), Diags, LangOpts,
                   SourceMgr, HeaderInfo, ModLoader,
                   /*IILookup =*/nullptr,
                   /*OwnsHeaderSearch =*/false);
+  // Ensure we can get expanded locations in presence of implicit includes.
+  // These are different than normal includes since predefines buffer doesn't
+  // have a valid insertion location.
+  PP.setPredefines("#include \"/implicit-header.h\"");
+  FileMgr.getVirtualFile("/implicit-header.h", 0, 0);
   PP.Initialize(*Target);
   PP.EnterMainSourceFile();
 

clang/unittests/Lex/LexerTest.cpp

@@ -556,4 +556,17 @@ TEST_F(LexerTest, FindNextToken) {
   EXPECT_THAT(GeneratedByNextToken, ElementsAre("abcd", "=", "0", ";", "int",
                                                 "xyz", "=", "abcd", ";"));
 }
+
+TEST_F(LexerTest, CreatedFIDCountForPredefinedBuffer) {
+  TrivialModuleLoader ModLoader;
+  auto PP = CreatePP("", ModLoader);
+  while (1) {
+    Token tok;
+    PP->Lex(tok);
+    if (tok.is(tok::eof))
+      break;
+  }
+  EXPECT_EQ(SourceMgr.getNumCreatedFIDsForFileID(PP->getPredefinesFileID()),
+            1U);
+}
 } // anonymous namespace