[backported/clang-9][Preamble] Stop circular inclusion of main file when building preamblerelease_80-based

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https://reviews.llvm.org/D53866
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If a header file was processed for the second time, we could end up with
a wrong conditional stack and skipped ranges:

In the particular example, if the header guard is evaluated the second
time and it is decided to skip the conditional block, the corresponding
"#endif" is never seen since the preamble does not include it and we end
up in the Tok.is(tok::eof) case with a wrong conditional stack.

Detect the circular inclusion, emit a diagnostic and stop processing the
inclusion.

Fixes: QTCREATORBUG-20883
Change-Id: I02644ddb507db4033dd5c69920c8e10500f0121c
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index ce8aa5d112..5a6d530054 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -1581,7 +1581,7 @@ FileID SourceManager::translateFile(const FileEntry *SourceFile) const {
     if (MainSLoc.isFile()) {
       const ContentCache *MainContentCache
         = MainSLoc.getFile().getContentCache();
-      if (!MainContentCache) {
+      if (!MainContentCache || !MainContentCache->OrigEntry) {
         // Can't do anything
       } else if (MainContentCache->OrigEntry == SourceFile) {
         FirstFID = MainFileID;