How to make std::vector's operator[] compile doing bounds checking in DEBUG but not in RELEASE
I'm using Visual Studio 2008.
I'm aware that std::vector has bounds checking with the at() function and has undefined behaviour if you try to access something using the operator [] incorrectly (out of range).
I'm curious if it's possible to compile my program with the bounds checking. This way the operator[] would use the at() function and throw a std::out_of_range whenever something is out of bounds.
The release mode would be compiled without bounds checking for operator[], so the performance doesn't degrade.
I came into thinking about this because I'm migrating an app that was written using Borland C++ to Visual Studio and in a small part of the code I have this (with i=0, j=1):
v[i][j]; //v is a std::vector<std::vector<int> >
The size of the vector 'v' is [0][1] (so element 0 of the vector has only one element). This is undefined behaviour, I know, but Borland is returning 0 here, VS is crashing. I like the crash better than returning 0, so if I can get more 'crashes' by the std::out_of_range exception being thrown, the migration would be completed faster (so it would expose more bugs that Borland was hiding).
Answer
Visual Studio 2005 and 2008 already do bounds-checking on operator[] by default, in both debug and release builds.
The macro to control this behavior is _SECURE_SCL. Set it to 0 to disable bounds-checking.
Their current plan in VS2010 is to disable bounds-checking by default in release builds, but keep it on in debug. (The macro is also getting renamed to _ITERATOR_DEBUG_LEVEL. I don't know if there's any formal documentation available on it yet, but it has been mentioned here and here)