[PCH] Fixed preamble breaking with BOM presence (and particularly, fluctuating BOM presence)
This patch fixes broken preamble-skipping when the preamble region includes a byte order mark (BOM). Previously, parsing would fail if preamble PCH generation was enabled and a BOM was present.
This also fixes preamble invalidation when a BOM appears or disappears. This may seem to be an obscure edge case, but it happens regularly with IDEs that pass buffer overrides that never (or always) have a BOM, yet the underlying file from the initial parse that generated a PCH might (or might not) have a BOM.
I've included a test case for these scenarios.
Differential Revision: https://reviews.llvm.org/D37491
llvm-svn: 313796
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index e129499..1f9a469 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -516,9 +516,9 @@
// If we've been asked to skip bytes in the main file (e.g., as part of a
// precompiled preamble), do so now.
if (SkipMainFilePreamble.first > 0)
- CurLexer->SkipBytes(SkipMainFilePreamble.first,
- SkipMainFilePreamble.second);
-
+ CurLexer->SetByteOffset(SkipMainFilePreamble.first,
+ SkipMainFilePreamble.second);
+
// Tell the header info that the main file was entered. If the file is later
// #imported, it won't be re-entered.
if (const FileEntry *FE = SourceMgr.getFileEntryForID(MainFileID))