What C++ version(s) should our C++ backend require?

[steven-johnson]

It looks like our C++ backend generates code that tries to assume only C++98 (e.g. it inserts static_assert calls bracketed with checks of __cplusplus >= 201103L).

Should we consider upgrading the requirement for the code we generate, to be at least C++11?

(Note: we should really stop calling it the "C backend" as it hasn't been plain C in, uh, ever?)

[vksnk]

I think it's already using C++11 in a few places, for example:

• nullptr (https://github.com/halide/Halide/blob/master/src/CodeGen_C.cpp#L209)
• constexpr (https://github.com/halide/Halide/blob/master/src/CodeGen_C.cpp#L171)

At some point I tried to compile generated code with C++98 and it didn't work right away (mostly because of what mentioned above), but it wasn't too difficult to fix (and I sort of already assumed that C++11 is assumed, so just fixed it locally).