Boost C++ Libraries: Ticket #2200: Bad memory management in algorithm::is_any_of

component, milestone changed; owner set

Marshall Clow — Mon, 18 Aug 2008 17:13:58 GMT

owner set to Pavol Droba
component None → string_algo
milestone Boost 1.36.0 → To Be Determined

status changed; resolution set

Pavol Droba — Mon, 18 Aug 2008 18:34:44 GMT

status new → closed
resolution → fixed

Thanks for spotting that out. I have just commited a fix into the trunk.

Thu, 21 Aug 2008 11:46:42 GMT

This doesn't fix the self-assignment problem. If we have code like
   is_any_of<char> foo("abcdefghijklmnopqrstuvwxyz");
   foo = foo;

then the operator= as currently written will delete this->m_Storage.m_dynSet (which is the same thing as Other.m_Storage.m_dynSet), and replace it with garbage. There are two possible ways to fix this. The first is to put the following code at the beginning of operator=
    if (this == &Other) return *this;

The second is to do the following: If *this and Other both allocate memory, check whether Other->m_Size is less than or equal to this->m_Size. If it is, then we don't have to reallocate this->m_Storage.m_dynSet. It will already have enough space allocated to hold the string from Other. It might have more space allocated than necessary, but that is no big deal. This saves us an unnecessary reallocation in some cases, including the self-assignment case.

Pavol Droba — Thu, 21 Aug 2008 14:50:04 GMT

Ok, I have used the combination of both. Self assignment case is tested at the beginning and the new space is not allocate if newsize <= size < 2*newsize.