At 20:55 19.05.2015, Mikhail Maltsev wrote: >On 05/19/2015 08:31 PM, Norbert Lange wrote: >> Hello, >> >> I know that using a class after a destructor is called is a nasty >> thing and I already changed the code, but I am curious if gcc is >> allowed by the standard to eliminate stores to member variables. >> >> I had code similar to the following: >> >> Destructor: >> if (_pAlloc) free(_pAlloc); >> _pAlloc = 0; >> _SomeData = 0; >> >> what happened was that I explicitly called the destructor for >> "cleanup" in another method. The free was called, and after the >> instance went out of scope it was called again with the same address. > >Yes, that is allowed, because your program invokes undefined behavior. >According to ISO C++11 standard: >12.4. <...> "Once a destructor is invoked for an object, the object no >longer exists; the behavior is undefined if the destructor is invoked >for an object whose lifetime has ended (3.8). [ Example: if the >destructor for an automatic object is explicitly invoked, and the block >is subsequently left in a manner that would ordinarily invoke implicit >destruction of the object, the behavior is undefined. ? end example ]" I think he's asking not about the double delete but the fact that the member was seemingly not zeroed when the second call was made. Two possibilities come to mind: 1. The debugger showed outdated values. 2. The object goes out of scope after the destructor so it doesn't matter if _SomeData was set to 0 or not, no one can access it (legally) anyway. Therefore it seems that gcc can omit this write unless it's volatile or so. Similar to the warning "variable is set but not used" -> no need to do it. bye Fabi
