From c9dde4f9572423723d9490336799f68050dfefa6 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 25 Feb 2008 21:38:21 +0000 Subject: [PATCH] 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 --- Lex/HeaderSearch.cpp | 40 ++++++++++------------------------------ 1 file changed, 10 insertions(+), 30 deletions(-) diff --git a/Lex/HeaderSearch.cpp b/Lex/HeaderSearch.cpp index 899c9d87a9..44ae35c8b7 100644 --- a/Lex/HeaderSearch.cpp +++ b/Lex/HeaderSearch.cpp @@ -228,22 +228,12 @@ const FileEntry *HeaderSearch::LookupFile(const char *FilenameStart, 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 @@ LookupSubframeworkHeader(const char *FilenameStart, } // 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; }