add typealiases for exact C-compatible types

[vtjnash]

some more typealias's for consideration in the list that I forgot initially (in decreasing order of my interest level of actually having them added):

typealias Cfloat Float32
typealias Cdouble Float64
typealias Cstring Ptr{Uint8}
typealias Cargv Ptr{Ptr{Uint8}}
typealias Cptr Ptr{Void}

(travis build fails because I'm using OS_NAME before build_h.jl got included in the sysimg. I think it should be moved much earlier)

[nolta]

Could we rename Cshortint, Cushortint, Cptrdiff, and Csize to Cshort, Cushort, Cptrdiff_t, and Csize_t?

I'm not sure we need Cstring, Cargv, & Cptr because Ptr{Cchar}, Ptr{Ptr{Cchar}}, & Ptr{Void} are pretty clear.

[StefanKarpinski]

I agree with @nolta's suggestions here. Also like having these aliases. Thanks, @vtjnash.

[stevengj]

Nice! I think we should have Cstring if only because it is more readable than Ptr{Cchar}.

[vtjnash]

It wasn't clear to me whether Cptrdiff_t or Cptrdiff was more correct. By analogy between Julia and C99 types, I dropped the _t, but I if those are well known enough on their own, I can follow @nolta's suggestion.

[stevengj]

I would just delete it, to be honest. The only real reason to have complex integers is for fixed-point arithmetic, as far as I can tell, but fixed-point complex arithmetic makes very little sense on any architecture with hardware multipliers.

If Julia ever begins to target embedded systems, you could always add this later, or the programmer could just use ComplexPair{Cint} manually, but adding this obcure and easily misused nonstandard type now seems to me like it does more harm than good.

[vtjnash]

would it make sense to add
typealias Carray Ptr{Void}
as a declaration mostly for use in Julia type declarations (since I've found it pretty common that someone expects julia's Array type is equivalent to a Cptr)

[stevengj]

Carray seems to break the convention that Cfoo corresponds to C type foo; this inconsistency seems unhelpful to me. Ptr{T} is clearer (since CT* is out of the question). On the other hand, I like Cstring, so I am inconsistent myself.

[StefanKarpinski]

I agree with @stevengj about Carray.

[vtjnash]

there's also the possibility of typealias Carray Ptr (or is that typealias Carray{T} Ptr{T}?). either way, i think this is good to merge now, without it

i imagined that you could reasonably have in your C code typedef char *string, so that Cstring is consistent. it's less clear to me what an array in c actually is since it can be either [] or * depending on context, so the idea that it is simply a Ptr{T} isn't as consistent

[stevengj]

You have (on non-Windows):

typealias Culong Int

Shouldn't this be Uint?

[pao]

@stevengj Looks like Jeff patched it up after the merge.