Add more integer conversions

[mrzv]

Without the changes in cast.h, on Linux, I'm unable to return unsigned long long from a function (works on Mac). Without the changes to int_ (at least the constructor from unsigned), I cannot do things like py::int_((uint32_t) 1).

[mrzv]

Judging by the failed checks, different compilers behave very differently.

[wjakob]

Yeah, it's tricky.. The behavior is also quite different on whether you compile for 32 bit or 64 bit platforms because size_t will change type and potentially collide with some overloads.

[wjakob]

By the way: I didn't unterstand why you can't return unsigned long long on Linux. Isn't that the same as uint64_t (for which there is a converter)?

[mrzv]

I don't understand why it happens, but if I define a function,

m.def("test", []() -> unsigned long long { return 1; });

compile it on Linux (without adding the lines to cast.h) and then call it from Python, I get:

In [4]: test()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-ea594c21b25d> in <module>()
----> 1 test()

TypeError: Unable to convert function return value to a Python type! The signature was
        () -> unsigned long long

[wjakob]

FYI: I committed a few more integer overloads for int_::int_(). I still don't get the issue with regards to returning long long from your code. Isn't that the same as int64_t? (so the existing overloads should be triggered)

[mrzv]

Have you confirmed it? Do you have access to Linux? For me it happens only under Linux (not under OS X), but it does happen. I don't understand it either: as you say, the existing overloads should get triggered. It could be a compiler bug, but it happens both with GCC 5.2 and Clang 3.7.

[wjakob]

I could not reproduce it yet. However, I have just committed another attempt to just make integer type handling completely generic using a template construction. Can you please retry with the latest version?

[wjakob]

(see 60c36db)

[mrzv]

Yes, it works! (And a nice solution, I might add. Comparing sizeof feels cleaner than explicitly spelling out all the types.) Thanks for fixing it.

[wjakob]

Great -- closing this then.