www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - betterC examples?

reply sfp <sfp hush.ai> writes:
I'm developing a C library with Cython bindings, built using 
CMake. I'd like to use D with -betterC to write some new code 
where it would be handy to have access to some more advanced 
language features to keep things readable. For my domain, C is 
totally fine 99% of the time, and rewriting a bunch of C code 
that's already tested and works nicely isn't a priority for me. I 
would like to develop new "modules" using -betterC and freely mix 
them into my existing C code without it being a headache.

So, it would be helpful to see some real -betterC examples. They 
don't need to polished, but substantial enough to help me get my 
bearings. Are there any out there that use CMake? This seems like 
it should be natural: start with a C or C++ CMake project (common 
enough!), and work D into the mix. I'm aware of cmake-d, but 
haven't taken too close of a look at it. It doesn't look like 
it's being actively developed.

To be clear, I'm mostly interested in examples that show how to 
structure a project. I'd like to know what the best way to start 
using D in my current project is, how to call D from C, and how 
to call C from D.

Thanks!
Apr 30 2021
next sibling parent reply bachmeier <no spam.net> writes:
On Friday, 30 April 2021 at 22:22:05 UTC, sfp wrote:

 I'm developing a C library with Cython bindings, built using 
 CMake. I'd like to use D with -betterC to write some new code 
 where it would be handy to have access to some more advanced 
 language features to keep things readable. For my domain, C is 
 totally fine 99% of the time, and rewriting a bunch of C code 
 that's already tested and works nicely isn't a priority for me. 
 I would like to develop new "modules" using -betterC and freely 
 mix them into my existing C code without it being a headache.

 [...]


There is a blog series 
https://dlang.org/blog/the-d-and-c-series/#betterC
Apr 30 2021
parent reply sfp <sfp hush.ai> writes:
On Friday, 30 April 2021 at 23:06:48 UTC, bachmeier wrote:

 There is a blog series 
 https://dlang.org/blog/the-d-and-c-series/#betterC


Thanks for the link.

I read through these, but they don't address my question. The 
first two posts are about specific -betterC features and the 
third one is about a total conversion from C to -betterC of a one 
or two file program. It's very cool that you can do the 
conversion so is easily, but this isn't my goal.
Apr 30 2021
parent Alain De Vos <devosalain ymail.com> writes:
https://dlang.org/spec/interfaceToC.html
Apr 30 2021
prev sibling parent reply Mike Parker <aldacron gmail.com> writes:
On Friday, 30 April 2021 at 22:22:05 UTC, sfp wrote:


 To be clear, I'm mostly interested in examples that show how to 
 structure a project. I'd like to know what the best way to 
 start using D in my current project is, how to call D from C, 
 and how to call C from D.


There is nothing special about the structure of a BetterC 
_project_. It's just a D project without the full feature set, so 
you can structure it in whatever way makes sense to you in terms 
of packages and modules.

As for the code, your main function should be `extern(C)`. 
Functions you want to make available to the C side should also be 
`extern(C)`, and will need equivalent declarations in C. DMD has 
an experimental feature to generate C headers for you via the 
`-HC` (`dmd -HC=?` for options). Then all that's left is to link 
the C objects into D or the D objects into C.

Beyond that, it's just a matter of making use of a limited subset 
of D features:

https://dlang.org/spec/betterc.html

I'm unaware of any specific open source projects that do what 
you're looking to (integrate new D code into an existing C 
project) especially any using CMake. But I would approach by 
isolating the new D code as a library. Then you can structure it 
however you like and just add the library to your C project's 
dependencies.

Alternatively, you could add individual D modules to your source 
tree and configure CMake such that they are compiled with a D 
compiler and a header generated for each.

I mean, there's no one way to go about this. But whatever you end 
up doing, please consider writing it up in a blog post for the D 
blog (email me at aldacron gmail.com when you're ready) 
describing how you approached it, then your project could be an 
example for someone else.
Apr 30 2021
parent reply Mike Parker <aldacron gmail.com> writes:
On Saturday, 1 May 2021 at 01:29:05 UTC, Mike Parker wrote:


 As for the code, your main function should be `extern(C)`. 
 Functions you want to make available to the C side should also 
 be `extern(C)`, and will need equivalent declarations in C. DMD 
 has an experimental feature to generate C headers for you via 
 the `-HC` (`dmd -HC=?` for options). Then all that's left is to 
 link the C objects into D or the D objects into C.


Forgot to talk about going the other way. You'll need to declare 
in D any C functions you'd like to call, also as `extern(C)`, 
with the appropriate type translations. There are posts about 
that on the D Blog:

https://dlang.org/blog/the-d-and-c-series/

Some documentation here:

https://dlang.org/spec/interfaceToC.html

A page on the D Wiki:

https://wiki.dlang.org/D_binding_for_C

And a rather lengthy chapter in my book 'Learning D'. (Email me 
about that chapter if you'd like).
Apr 30 2021
parent sfp <sfp hush.ai> writes:
On Saturday, 1 May 2021 at 01:52:00 UTC, Mike Parker wrote:

 ...


Mike, thanks for your detailed replies. They're both very helpful.

What you described is what I figured I would need to do if I were 
to roll my own solution. I was hoping someone would have gone 
through the trouble of doing this already, but it seems like 
maybe no one has.

Since this will require a bit more up front effort, I won't have 
a chance to give this as a go until the middle of summer or so. 
But I would be happy to put together a simple example as a GitHub 
repository and write it up for the D blog when I do so in case 
it's helpful to other people.

I'll also send you an email about that chapter (I'm assuming it's 
not publicly available).

If anyone else *does* know of some real-world examples, or has 
tried this kind of thing and has instructive war stories, please 
loop me in.
May 01 2021