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c++castingreinterpret-castarrays

Is reinterpret_cast to C-style array illegal C++11?

Why is the following code frowned upon?

double d[4] = {0,1,2,3};
reinterpret_cast<double[2]>(d);

GCC declares it an invalid cast from type 'double*' to type 'double [2]' and clang declares that reinterpret_cast from 'double *' to 'double [2]' is not allowed

Now in case the intent is not obvious, I would like this code to return a double[2] that contains {0,1}, pretty much like a reinterpret_cast<double*>(d) would. (Hence I know it would work with pointers, so that's not what I'm asking)

Solution

  • Both compilers are correct.

    reinterpret_cast is not a hammer, it's a powerful precision tool. All uses of reinterpret_cast have to involve at least one pointer or reference type as the source or as the destination, except for the degenerate case of an identity integral conversion (i.e. reinterpret_cast from int to int is allowed and does nothing.)