C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Catching vector index out of bounds          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Biff Guest Posted: Sun Jan 30, 2005 5:24 pm    Post subject: Catching vector index out of bounds Is there a common way to check for vector indexes being in bounds? My version of the STL has no such check, even in debug builds. I was considering deriving a class from Vector with its own operator[], and using that in my code instead of std::vector. Then I'd use an #ifdef _DEBUG switch which typedef'ed my vector class name to std::vector if in release or used the derived class if in debug. Does that sound reasonable? Is there an easier and more common way? Back to top Cy Edmunds Guest Posted: Sun Jan 30, 2005 5:27 pm    Post subject: Re: Catching vector index out of bounds "Biff" <fksl (AT) fcvie (DOT) com> wrote Quote: Is there a common way to check for vector indexes being in bounds? My version of the STL has no such check, even in debug builds. I was considering deriving a class from Vector with its own operator[], and using that in my code instead of std::vector. Then I'd use an #ifdef _DEBUG switch which typedef'ed my vector class name to std::vector if in release or used the derived class if in debug. Does that sound reasonable? Is there an easier and more common way? Look at the function "at" which should already be in your std::vector. I think it does what you want. -- Cy http://home.rochester.rr.com/cyhome/ Back to top Mike Wahler Guest Posted: Sun Jan 30, 2005 7:12 pm    Post subject: Re: Catching vector index out of bounds "Biff" <fksl (AT) fcvie (DOT) com> wrote Quote: Is there a common way to check for vector indexes being in bounds? My version of the STL has no such check, even in debug builds. I was considering deriving a class from Vector with its own operator[], and using that in my code instead of std::vector. Then I'd use an #ifdef _DEBUG switch which typedef'ed my vector class name to std::vector if in release or used the derived class if in debug. Does that sound reasonable? Is there an easier and more common way? std::vector::at() The argument is the same you'd use for operator[](), but if given an out-of-bounds value, throws an exception (of type 'std::out_of_range'). -Mike Back to top Stephen Howe Guest Posted: Mon Jan 31, 2005 3:09 am    Post subject: Re: Catching vector index out of bounds Quote: Is there a common way to check for vector indexes being in bounds? My version of the STL has no such check, even in debug builds. I was considering deriving a class from Vector with its own operator[], and using that in my code instead of std::vector. Then I'd use an #ifdef _DEBUG switch which typedef'ed my vector class name to std::vector if in release or used the derived class if in debug. Does that sound reasonable? Is there an easier and more common way? Use member function at() I sometimes use the following for vector and deque: #if defined(_DEBUG) #define AT(x) at(x) #else #define AT(x) operator[](x) #endif and then have something like std::vector<int> v; int i = v.AT(0); For debug builds, access is ranged-checked For release builds, access is not ranged-checked Of course there is nothing to stop you from doing int j = v[1]; int k = v.at(2); when you defiintely want no range checking or range checking. Stephen Howe Back to top E. Robert Tisdale Guest Posted: Mon Jan 31, 2005 5:55 am    Post subject: Re: Catching vector index out of bounds Biff wrote: Quote: Is there a common way to check for vector indexes being in bounds? You could use member function reference at(size_type __n) { _M_range_check(__n); return (*this)[__n]; } const_reference at(size_type __n) const { _M_range_check(__n); return (*this)[__n]; } but that throws an exception and is *not* appropriate if you are trying to trap programming errors (bugs). Quote: My version of the STL has no such check, even in debug builds. I was considering deriving a class from Vector with its own operator[] and using that in my code instead of std::vector. Then I'd use an #ifdef _DEBUG switch which typedef'ed my vector class name to std::vector if in release or used the derived class if in debug. Does that sound reasonable? It sounds very reasonable. Quote: Is there an easier and more common way? My GNU C++ compiler defines members: reference operator[](size_type __n) { return *(begin() + __n); } const_reference operator[](size_type __n) const { return *(begin() + __n); } in /usr/include/c++/3.4.0/bits/stl_vector.h You could redefine them: reference operator[](size_type __n) { assert(__n < this->size()); return *(begin() + __n); } const_reference operator[](size_type __n) const { assert(__n < this->size()); return *(begin() + __n); } Anyway, you should check your implementation. You might find that this has already been done for you. 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