[Parse] Split incremental-extensions (#65683)

The preprocessor `IncrementalProcessing` option was being used to
control whether or not to teardown the lexer or run the end of
translation unit action. In D127284 this was merged with
`-fincremental-extensions`, which also changes top level parsing.

Split these again so that the former behavior can be achieved without
the latter (ie. to allow managing lifetime without also changing
parsing).

Resolves rdar://113406310.

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 8de78a1..f0381c1 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -146,6 +146,10 @@ Preprocessor::Preprocessor(std::shared_ptr<PreprocessorOptions> PPOpts,
     Ident_AbnormalTermination = nullptr;
   }
 
+  // Default incremental processing to -fincremental-extensions, clients can
+  // override with `enableIncrementalProcessing` if desired.
+  IncrementalProcessing = LangOpts.IncrementalExtensions;
+
   // If using a PCH where a #pragma hdrstop is expected, start skipping tokens.
   if (usingPCHWithPragmaHdrStop())
     SkippingUntilPragmaHdrStop = true;