Fix source build for Julia 1.4

[Gnimuc]

Misc. update for LLVM 8.

Now the package can be built successfully, but I got these errors when using the package:

julia> using Cxx
58
BuiltinType 0x7f8de2802fc0 'unsigned long'
/Cxx.cpp:1:1: error: 'data' following the 'template' keyword does not refer to a template
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:1242:23: note: declared as a non-template here
    const value_type* data() const _NOEXCEPT  {return _VSTD::__to_raw_pointer(__get_pointer());}
                      ^
/Cxx.cpp:1:1: error: 'size' following the 'template' keyword does not refer to a template
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:946:41: note: declared as a non-template here
    _LIBCPP_INLINE_VISIBILITY size_type size() const _NOEXCEPT

Hi @Keno, could you give it a review?

[innerlee]

I'm having precompiling error on 1.4.

julia> using Cxx
[ Info: Precompiling Cxx [a0b5b9ef-44b7-5148-a2d1-f6db19f3c3d2]
ERROR: LoadError: LoadError: AssertionError: isdir(cxxclangdir)
Stacktrace:
 [1] collectClangHeaders!(::Array{Tuple{String,Int32},1}) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:
380
 [2] collectAllHeaders!(::Array{Tuple{String,Int32},1}, ::Bool) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initializati
on.jl:390
 [3] collectAllHeaders(::Bool) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:393
 [4] top-level scope at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:423
 [5] include(::Module, ::String) at ./Base.jl:377
 [6] include(::String) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/Cxx.jl:144
 [7] top-level scope at /home/lizz/.julia/packages/Cxx/7Ms5P/src/Cxx.jl:170
 [8] include(::Module, ::String) at ./Base.jl:377
 [9] top-level scope at none:2
 [10] eval at ./boot.jl:331 [inlined]
 [11] eval(::Expr) at ./client.jl:449
 [12] top-level scope at ./none:3
in expression starting at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:423
in expression starting at /home/lizz/.julia/packages/Cxx/7Ms5P/src/Cxx.jl:170
ERROR: Failed to precompile Cxx [a0b5b9ef-44b7-5148-a2d1-f6db19f3c3d2] to /home/lizz/.julia/compiled/v1.4/Cxx/ESGkI_BmH2
D.ji.
Stacktrace:
 [1] error(::String) at ./error.jl:33
 [2] compilecache(::Base.PkgId, ::String) at ./loading.jl:1272
 [3] _require(::Base.PkgId) at ./loading.jl:1029
 [4] require(::Base.PkgId) at ./loading.jl:927
 [5] require(::Module, ::Symbol) at ./loading.jl:922

The build step is okay.

[Gnimuc]

@innerlee it looks like Cxx failed to detect your system-headers. You could try to print some of those variables around the error site to see why it cannot do that.

[innerlee]

Could you give some instructions on how to do it? I'm not very familiar with cpp

[Gnimuc]

The following error occurred in the Julia side, if you're working in REPL, simply typing 1+Ctrl+Q will bring you to the first error site. ;)

julia> using Cxx
[ Info: Precompiling Cxx [a0b5b9ef-44b7-5148-a2d1-f6db19f3c3d2]
ERROR: LoadError: LoadError: AssertionError: isdir(cxxclangdir)
Stacktrace:
 [1] collectClangHeaders!(::Array{Tuple{String,Int32},1}) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:
380
 [2] collectAllHeaders!(::Array{Tuple{String,Int32},1}, ::Bool) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initializati
on.jl:390
 [3] collectAllHeaders(::Bool) at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:393
 [4] top-level scope at /home/lizz/.julia/packages/Cxx/7Ms5P/src/initialization.jl:423
 [5] include(::Module, ::String) at ./Base.jl:377

[innerlee]

Thanks! Like magic haha. I'm around somewhere like

The 3rd error site:

        if JLOptions().use_compiled_modules != 0
            if (0 == ccall(:jl_generating_output, Cint, ())) || (JLOptions().incremental != 0)
                # spawn off a new incremental pre-compile task for recursive `require` calls
                # or if the require search declared it was pre-compiled before (and therefore is e$
                cachefile = compilecache(pkg, path)                              <------------------- THIS LINE
                if isa(cachefile, Exception)
                    if precompilableerror(cachefile)
                        verbosity = isinteractive() ? CoreLogging.Info : CoreLogging.Debug
                        @logmsg verbosity "Skipping precompilation since __precompile__(false). Im$
                    else
                        @warn "The call to compilecache failed to create a usable precompiled cach$
                    end
                    # fall-through to loading the file locally
                else
                    m = _require_from_serialized(cachefile)
                    if isa(m, Exception)
                        @warn "The call to compilecache failed to create a usable precompiled cach$
                    else
                        return
                    end
                end
            end
        end

Which variable should I print then? I tried to put some println before that line, but nothing got printed.

[Gnimuc]

Could you run this and check what you got?
joinpath(get(ENV, "BASE_JULIA_BIN", Sys.BINDIR), "..", "lib", "clang", llvmver, "include") |> isdir

If the ans is no, please check the path.jl generated in the dir: Cxx/deps/, it might be wrong.

BTW, Cxx is still not fully functional with this PR. I'm trying to get a clue how to fix those underlying Clang-related errors, but making nearly no progress, so I would recommend using Julia 1.3.x for now if you'd like to use Cxx.jl.

[innerlee]

Okay, I will wait for this pr then. I was trying to play with some basic cpp codes, and using this cxx repl as a live notebook. Anyway, printing debug is always a choice for me :D