How to protect code from crashes in this situation
int arr[ 5 ] = { 0 };
int i = 8; // out of bounds
arr[ i ] = 8;
I know that I can just check i like this if( i < 0 || i > 5 ) ....
I also know about SEH in Visual Studio, but it looks li开发者_StackOverflow中文版ke not working solution.
__try { /* code */ }
__except(GetExceptionCode() == EXCEPTION_ARRAY_BOUNDS_EXCEEDED)
This is not working. As I see SEH working in situations like divide to 0, access protected pages ... How can I protect my program from crashes?
There is no guarantee that SEH will catch this - it depends on your hardware detecting the access , which does not happen for all invalid array accesses. If you want to be sure of catching it, use the standard C++ std::vector
container instead of an array, and access it via its at()
member function, rather than the []
operator - this will raise a standard C++ exception if the access is invalid.
You cannot protect yourself from this. If you want, you have to use another language that checks for you. C and C++ demand that you check yourself that you write safe code.
An alternative may be to wrap the array into a struct...
template<typename E, std::size_t s>
struct array {
E &operator[](std::ptrdiff_t i) {
assert(i < s && "out of range!");
return d[i];
}
E const &operator[](std::ptrdiff_t i) const {
assert(i < s && "out of range!");
return d[i];
}
typedef E underlying_array[s];
underlying_array &raw() { return d; }
underlying_array const &raw() const { return d; }
E d[s];
};
array<int, 5> arr = { 0 };
arr[8] = 8; /* assert will ring */
foo(arr.raw()); /* pass as an int[5] */
That class is provided by boost
and C++0x too (however, without a raw
function), but error checking is not required for them.
Use proper containers like std::vector and catch the exceptions?
You have a couple of options:
- don't use raw arrays (use std::vector or boost::array instead)
- don't use C++
the only other option is to write code that does not contain any out-of-bounds errors
There is absolutely no way to reliably detect out-of-bounds errors on raw arrays in C++.
You could just catch the access violation that sometimes occurs, but that won't give you a correct program. You'll still go out of bounds in many other cases, overwriting previously allocated memory and corrupting other parts of your program.
精彩评论