clarify comment, this is undefined behavior in any case, even if it only
bits VC++ right now.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@47565 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Lex/HeaderSearch.cpp b/Lex/HeaderSearch.cpp
index 899c9d8..44ae35c 100644
--- a/Lex/HeaderSearch.cpp
+++ b/Lex/HeaderSearch.cpp
@@ -228,22 +228,12 @@
if (const FileEntry *FE = FileMgr.getFile(TmpDir.begin(), TmpDir.end())) {
// Leave CurDir unset.
// This file is a system header or C++ unfriendly if the old file is.
-
- // Note: Don't use:
//
- // getFileInfo(FE).DirInfo = getFileInfo(CurFileEnt).DirInfo;
- //
- // MSVC, behind the scenes, does this:
- //
- // PerFileInfo &pf1 = getFileInfo(CurFileEnt);
- // PerFileInfo &pf2 = getFileInfo(FE);
- // pf2.DirInfo = pf1.DirInfo
- //
- // The problem is that if there's a resize() of the FileInfo vector during
- // the getFileInfo(FE) call, pf1 will point to invalid data. To fix
- // this problem, make the assignment through a temporary.
- unsigned int tmp = getFileInfo(CurFileEnt).DirInfo;
- getFileInfo(FE).DirInfo = tmp;
+ // Note that the temporary 'DirInfo' is required here, as either call to
+ // getFileInfo could resize the vector and we don't want to rely on order
+ // of evaluation.
+ unsigned DirInfo = getFileInfo(CurFileEnt).DirInfo;
+ getFileInfo(FE).DirInfo = DirInfo;
return FE;
}
}
@@ -372,22 +362,12 @@
}
// This file is a system header or C++ unfriendly if the old file is.
-
- // Note: Don't use:
//
- // getFileInfo(FE).DirInfo = getFileInfo(ContextFileEnt).DirInfo;
- //
- // MSVC, behind the scenes, does this:
- //
- // PerFileInfo &pf1 = getFileInfo(ContextFileEnt);
- // PerFileInfo &pf2 = getFileInfo(FE);
- // pf2.DirInfo = pf1.DirInfo
- //
- // The problem is that if there's a resize() of the FileInfo vector during
- // the getFileInfo(FE) call, pf1 will point to invalid data. The solution
- // is to make the assignment through a temporary.
- unsigned int tmp = getFileInfo(ContextFileEnt).DirInfo;
- getFileInfo(FE).DirInfo = tmp;
+ // Note that the temporary 'DirInfo' is required here, as either call to
+ // getFileInfo could resize the vector and we don't want to rely on order
+ // of evaluation.
+ unsigned DirInfo = getFileInfo(ContextFileEnt).DirInfo;
+ getFileInfo(FE).DirInfo = DirInfo;
return FE;
}