Update helpers.jl with initial value for Ref{Cuint}

[david-macmahon]

Fixes #1137

[mkitti]

This is supposed to be a C99 bool aka _Bool. The appropriate type for the Ref should be Cuchar.

https://docs.hdfgroup.org/hdf5/develop/group___h5.html#ga70bfde4acd009cdd7bcd2f54c594e28a

[mkitti]

I think we also want to change to Cuchar here:

HDF5.jl/gen/api_defs.jl

Line 30 in 91ef284

@bind h5_is_library_threadsafe(is_ts::Ref{Cuint})::herr_t "Error determining thread safety"

[david-macmahon]

Yeah, I didn't realize/forgot that a lot of the api files are generated. I guess the generator doesn't provide an initial value when generating so it relies on having the type size correct. Maybe best to change it to is_ts = Ref{Cchar}() in helpers.jl and Cuchar in gen_api.jl. I can make the changes, but I don't have cycles to test them. Does CI regenerate the api files? I guess we should add a test for this, but how does one test something that relies on an uninitialized value being (or not being) a certain value?

[mkitti]

Once you change api_defs.jl, just run the gen_wrappers.jl script as indicated below. If you cannot, I would be happy to do it.

HDF5.jl/gen/gen_wrappers.jl

Line 2 in 91ef284

# Run `julia --project=.. gen_wrappers.jl`` to execute this script

[simonbyrne]

Maybe we should switch to Clang.jl-generated wrappers.

[mkitti]

I worked on that a few years ago in LibHDF5.jl:
https://github.com/mkitti/LibHDF5.jl/blob/main/src/bind.jl

In particular, this line:
https://github.com/mkitti/LibHDF5.jl/blob/712b6e306a15de37f748727b37676aca70ea0664/src/bind.jl#L434

And this line would have lead to the correct definition:
https://github.com/mkitti/LibHDF5.jl/blob/712b6e306a15de37f748727b37676aca70ea0664/src/bind.jl#L192

The problem is that we also have these custom error messages as well.

[mkitti]

I'm going to try to push this through soon