[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, 6 insertions, 0 deletions

diff --git a/clang/unittests/Basic/SourceManagerTest.cpp b/clang/unittests/Basic/SourceManagerTest.cpp
index f4bdd9c..850a08b 100644
--- a/clang/unittests/Basic/SourceManagerTest.cpp
+++ b/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();