Allow for unfinished #if blocks in preambles

Previously, a preamble only included #if blocks (and friends like
ifdef) if there was a corresponding #endif before any declaration or
definition. The problem is that any header file that uses include guards
will not have a preamble generated, which can make code-completion very
slow.

To prevent errors about unbalanced preprocessor conditionals in the
preamble, and unbalanced preprocessor conditionals after a preamble
containing unfinished conditionals, the conditional stack is stored
in the pch file.

This fixes PR26045.

Differential Revision: http://reviews.llvm.org/D15994

llvm-svn: 304207

1 files changed, 1 insertions, 0 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index d660638a1e8..d968882174f 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -1999,6 +1999,7 @@ ASTUnit *ASTUnit::LoadFromCommandLine(
   PreprocessorOptions &PPOpts = CI->getPreprocessorOpts();
   PPOpts.RemappedFilesKeepOriginalName = RemappedFilesKeepOriginalName;
   PPOpts.AllowPCHWithCompilerErrors = AllowPCHWithCompilerErrors;
+  PPOpts.GeneratePreamble = PrecompilePreambleAfterNParses != 0;
   
   // Override the resources path.
   CI->getHeaderSearchOpts().ResourceDir = ResourceFilesPath;