[clang] aab50af - SourceManager: Use the same fake SLocEntry whenever it fails to load

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

Author: Duncan P. N. Exon Smith
Date: 2020-10-26T20:56:28-04:00
New Revision: aab50af8c18ab2eb2149bb516c8a0993ffc5abb7

URL: https://github.com/llvm/llvm-project/commit/aab50af8c18ab2eb2149bb516c8a0993ffc5abb7
DIFF: https://github.com/llvm/llvm-project/commit/aab50af8c18ab2eb2149bb516c8a0993ffc5abb7.diff

LOG: SourceManager: Use the same fake SLocEntry whenever it fails to load

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`.

Differential Revision: https://reviews.llvm.org/D89748

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
index ec9b2b7d0cfd..765cec465f9d 100644
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -693,7 +693,7 @@ class SourceManager : public RefCountedBase<SourceManager> {
   ///
   /// 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.
   ///
@@ -775,6 +775,8 @@ class SourceManager : public RefCountedBase<SourceManager> {
 
   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>;

diff  --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index 6eae0f06a122..88f95d18ddf1 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -434,9 +434,11 @@ const SrcMgr::SLocEntry &SourceManager::loadSLocEntry(unsigned Index,
     // 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;
     }
   }