From 27006195205f3f3e9d389a46bc29e80458621194 Mon Sep 17 00:00:00 2001 From: Marshall Clow Date: Sat, 4 Jun 2016 16:16:59 +0000 Subject: [PATCH] Don't call memmove when there's nothing to move. Fixes PR#27978. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@271794 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/fstream | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/fstream b/include/fstream index d51da45d8..3cb3b13bd 100644 --- a/include/fstream +++ b/include/fstream @@ -606,7 +606,9 @@ basic_filebuf<_CharT, _Traits>::underflow() } else { - memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_); + _LIBCPP_ASSERT ( !(__extbufnext_ == NULL && (__extbufend_ != __extbufnext_)), "underflow moving from NULL" ); + if (__extbufend_ != __extbufnext_) + memmove(__extbuf_, __extbufnext_, __extbufend_ - __extbufnext_); __extbufnext_ = __extbuf_ + (__extbufend_ - __extbufnext_); __extbufend_ = __extbuf_ + (__extbuf_ == __extbuf_min_ ? sizeof(__extbuf_min_) : __ebs_); size_t __nmemb = _VSTD::min(static_cast(__ibs_ - __unget_sz),