Comment the reasons for the strange little dance we do with the main file name for debug information
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99215 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index ad97d08..df1a24c 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -112,6 +112,10 @@
llvm::sys::Path AbsFileName(MainFileName);
AbsFileName.makeAbsolute();
+ // The main file name provided via the "-main-file-name" option contains just
+ // the file name itself with no path information. This file name may have had
+ // a relative path, so we look into the actual file entry for the main
+ // file to determine the real absolute path for the file.
std::string MainFileDir;
if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID()))
MainFileDir = MainFile->getDir()->getName();