[PATCH] D89748: SourceManager: Use the same fake SLocEntry whenever it fails to load

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith created this revision.
dexonsmith added a reviewer: teemperor.
Herald added a subscriber: ributzka.
dexonsmith requested review of this revision.

Instead of putting a fake `SLocEntry` at `LoadedSLocEntryTable[Index]`
when it fails to load in `SourceManager::loadSLocEntry`, allocate a fake
one. Unless someone is sniffing the address of the returned `SLocEntry`
(doubtful), this won't be a functionality change. Note that
`SLocEntryLoaded[Index]` wasn't being set to `true` either before or
after this change so no accessor is every going to look at
`LoadedSLocEntryTable[Index]`.

As a side effect, drop the `mutable` from `LoadedSLocEntryTable`.


https://reviews.llvm.org/D89748

Files:
  clang/include/clang/Basic/SourceManager.h
  clang/lib/Basic/SourceManager.cpp


Index: clang/lib/Basic/SourceManager.cpp
===================================================================
--- clang/lib/Basic/SourceManager.cpp
+++ clang/lib/Basic/SourceManager.cpp
@@ -434,9 +434,12 @@
     // If the file of the SLocEntry changed we could still have loaded it.
     if (!SLocEntryLoaded[Index]) {
       // Try to recover; create a SLocEntry so the rest of clang can handle it.
-      LoadedSLocEntryTable[Index] = SLocEntry::get(
-          0, FileInfo::get(SourceLocation(), *getFakeContentCacheForRecovery(),
-                           SrcMgr::C_User, ""));
+      if (!FakeSLocEntryForRecovery)
+        FakeSLocEntryForRecovery = std::make_unique<SLocEntry>(
+            SLocEntry::get(0, FileInfo::get(SourceLocation(),
+                                            *getFakeContentCacheForRecovery(),
+                                            SrcMgr::C_User, "")));
+      return *FakeSLocEntryForRecovery;
     }
   }
 
Index: clang/include/clang/Basic/SourceManager.h
===================================================================
--- clang/include/clang/Basic/SourceManager.h
+++ clang/include/clang/Basic/SourceManager.h
@@ -671,7 +671,7 @@
   ///
   /// Negative FileIDs are indexes into this table. To get from ID to an index,
   /// use (-ID - 2).
-  mutable SmallVector<SrcMgr::SLocEntry, 0> LoadedSLocEntryTable;
+  SmallVector<SrcMgr::SLocEntry, 0> LoadedSLocEntryTable;
 
   /// The starting offset of the next local SLocEntry.
   ///
@@ -753,6 +753,8 @@
 
   mutable std::unique_ptr<SrcMgr::ContentCache> FakeContentCacheForRecovery;
 
+  mutable std::unique_ptr<SrcMgr::SLocEntry> FakeSLocEntryForRecovery;
+
   /// Lazily computed map of macro argument chunks to their expanded
   /// source location.
   using MacroArgsMap = std::map<unsigned, SourceLocation>;


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