What Rust Can Do That Other Languages Can't

Re:What Rust Can Do That Other Languages Can't by rubber_duck on Monday February 06, 2017 @03:56AM (#13577720)

In C++ it's quite easy to get burned by keeping a reference to something where the owner went out of scope eg.

   class Foo {
      int bar;
      int& getBar() { return bar; } 
   }

if you take ref of bar and Foo goes out of scope well fuck. It gets even worse, eg. :

    vector<int> foo;
    int& bar = foo[i];
    foo.push_back(1)

that last line can cause foo to reallocate the buffer and bar is then invalid, meanwhile that code will compile without warnings (well I'm guessing it will I haven't done C++ in a year :) )

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Re:What Rust Can Do That Other Languages Can't by satbyy on Monday February 06, 2017 @04:22AM (#13577871)

Just hit 'Run' here: http://rextester.com/BDGO47890

You can see the program crash

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Re:What Rust Can Do That Other Languages Can't by rubber_duck on Monday February 06, 2017 @06:55AM (#13578615)

Nice, but the example crashes because you take a reference to uninitialized vector, if you initialize it and grow the vector I found that it will either keep "working fine" if you don't expect the data to change or randomly give garbage data - depending on compiler/stdlib - especially since the time when the buffer grows is implementation defined.

Here is a better example : http://rextester.com/MAJDQ8375

On VC++ it will return : Reference is 0 but value is 9

On clang it will return : Reference is 32579632 but value is 9

So let's say I wasn't mutating the 0 index, VC example would work fine at runtime and then clang would suddenly start giving garbage results. This has caused me week of debugging in a big code base.

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Re:What Rust Can Do That Other Languages Can't by satbyy on Monday February 06, 2017 @09:22AM (#13579603)

Thanks for the catch!

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Re:What Rust Can Do That Other Languages Can't by akie on Monday February 06, 2017 @04:21AM (#13577866)

Thank you! That clarifies it quite a bit. My C/C++ is too rusty to remember these internals...

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Re:What Rust Can Do That Other Languages Can't by saghm on Monday February 06, 2017 @02:45PM (#13583165)

> My C/C++ is too rusty

Pun intended?

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