[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

1 files changed, 13 insertions, 0 deletions

diff --git a/clang/unittests/Lex/LexerTest.cpp b/clang/unittests/Lex/LexerTest.cpp
index c68eed9..4cdabe0 100644
--- a/clang/unittests/Lex/LexerTest.cpp
+++ b/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