------- Comment #9 from fpbeekhof at gmail dot com 2009-03-17 13:11 ------- Subject: Re: generated memcpy causes trouble in assignment
paolo dot carlini at oracle dot com wrote: > ------- Comment #8 from paolo dot carlini at oracle dot com 2009-03-17 12:33 > ------- > Yes, if there is a bug, certainly it is not in libstdc++. Also, please find > somebody able to reproduce it, I can't. Someone should check whether the part that generates operator=() generates a memcpy(), in which case there is a bug because that cannot handle assignment to self, which implies overlapping memory areas, which in turn, as stated by the standard and confirmed by the existence of certain pre-fetch instructions, leads to undefined behavior. This reasoning is valid even if anyone, at any particular time, is able not to see the symptoms. If that bug is there, a possible fix would be to replace memcpy by memmove, as I have suggested. I don't know in what component gcc generates its operator=(), so if someone can tell me I'll assign it to that. Second thing to do is to re-open the bug because it is very real unless it has been fixed already in a later version. Third thing is to increase the priority, because this is likely to affect probably almost all C++ programs, and make all of their behavior undefined. I'm not familiar with gcc policies, and maybe someone can check if this has already been fixed, so I'll wait a few moments before doing these 3 things, to see if there are any reactions. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39480
