Why don't managed languages offer the ability to manually delete objects?

Question

Lets say you want to write a high performance method which processes a large data set. Why shouldn't developers have the ability to turn on manual memory management instead of being forced to move to C or C++?

void Process()
{
    unmanaged
    {
        Byte[] buffer;
        while (true)
        {
            buffer = new Byte[1024000000];

            // process

            delete buffer;
        } 
    }   
}

Answer 1

Because allowing you to manually delete a memory block while there may still be references to it (and the runtime has no way of knowing that without doing a GC cycle) can produce dangling pointers, and thus break memory safety. GC languages are generally memory-safe by design.

That said, in C#, in particular, you can do what you want already:

void Process()
{
    unsafe
    {
        byte* buffer;
        while (true)
        {
            buffer = Marshal.AllocHGlobal(1024000000);

            // process

            Marshal.FreeHGlobal(buffer);
        } 
    }   
}

Note that, as in C/C++, you have full pointer arithmetic for raw pointer types in C# - so buffer[i] or buffer+i are valid expressions.