From 2a8bf425bd0aff1a6406805c095d99089a1dfaae Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Wed, 30 Jun 2010 15:02:37 +0000 Subject: Rather than giving SmallPtrSetImpl a member field SmallArray which is magically replaced by a bigger array in SmallPtrSet (by overridding it), instead just use a pointer to the start of the storage, and have SmallPtrSet pass in the value to use. This has the disadvantage that SmallPtrSet becomes bigger by one pointer. It has the advantage that it no longer uses tricky C++ rules, and is clearly correct while I'm not sure the previous version was. This was inspired by g++-4.6 pointing out that SmallPtrSetImpl was writing off the end of SmallArray, which it was. Since SmallArray is replaced with a bigger array in SmallPtrSet, the write was still to valid memory. But it was writing off the end of the declared array type - sounds kind of dubious to me, like it sounded dubious to g++-4.6. Maybe g++-4.6 is wrong and this construct is perfectly valid and correctly compiled by all compilers, but I think it is better to avoid the whole can of worms by avoiding this construct. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107285 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/SmallPtrSet.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'lib/Support') diff --git a/lib/Support/SmallPtrSet.cpp b/lib/Support/SmallPtrSet.cpp index 68938fa..504e649 100644 --- a/lib/Support/SmallPtrSet.cpp +++ b/lib/Support/SmallPtrSet.cpp @@ -166,10 +166,13 @@ void SmallPtrSetImpl::Grow() { } } -SmallPtrSetImpl::SmallPtrSetImpl(const SmallPtrSetImpl& that) { +SmallPtrSetImpl::SmallPtrSetImpl(const void **SmallStorage, + const SmallPtrSetImpl& that) { + SmallArray = SmallStorage; + // If we're becoming small, prepare to insert into our stack space if (that.isSmall()) { - CurArray = &SmallArray[0]; + CurArray = SmallArray; // Otherwise, allocate new heap space (unless we were the same size) } else { CurArray = (const void**)malloc(sizeof(void*) * (that.CurArraySize+1)); @@ -197,7 +200,7 @@ void SmallPtrSetImpl::CopyFrom(const SmallPtrSetImpl &RHS) { if (RHS.isSmall()) { if (!isSmall()) free(CurArray); - CurArray = &SmallArray[0]; + CurArray = SmallArray; // Otherwise, allocate new heap space (unless we were the same size) } else if (CurArraySize != RHS.CurArraySize) { if (isSmall()) -- cgit v1.1