dstep ~api_notes

DStep

DStep is a tool for automatically generating D bindings for C and Objective-C libraries. This is implemented by processing C or Objective-C header files and output D modules. DStep uses the Clang compiler as a library (libclang) to process the header files.

Download

For the latest release see: releases/latest.

Pre-compiled binaries are available for macOS and Linux as 64 bit binaries and Windows as 32 and 64 bit binaries. The Linux binaries are completely statically linked and should work on all distros. The macOS binaries are statically linked against libclang requires no other dependencies than the system libraries. They should work on macOS Mavericks (10.9) and later. The Windows binaries require to install libclang. See the releases section.

Alternatively install via Dub

License

The source code is available under the Boost Software License 1.0

Building

Posix

Requirements

• libclang - http://clang.llvm.org - 10.0.0 or 9.0.0. The idea is that the two most recent versions of libclang are supported.
• A D compiler - The latest version of DMD or LDC
• Dub http://code.dlang.org/download (also shipped with the compilers)

Building

1. Install all requirements, see above
2. Clone the repository by running:

   $ git clone https://github.com/jacob-carlborg/dstep
   
   

3. Run dub build

A configuration script will try to automatically locate libclang by looking through a couple of default search paths. If libclang is not found in any of the default paths, please manually invoke the configuration script and specify the path to where libclang is installed using the --llvm-path flag.

$ ./configure --llvm-path /usr/lib/llvm-4.0

Windows

Requirements

• LLVM - http://llvm.org/releases/download.html - pre-built binaries for Windows. Has to be installed at the default location
• DMD - http://dlang.org/download.html - 2.071.0 or later
• Dub - http://code.dlang.org/download
• Visual Studio - for example Visual Studio Community

Building

1. Install all requirements, see above
2. Clone the repository by running:

   $ git clone git://github.com/jacob-carlborg/dstep.git
   
   

3. Run dub build --arch=x86_mscoff --build=release to build 32-bit version
4. Run dub build --arch=x86_64 --build=release to build 64-bit version

Remarks

Building 32-bit version requires a 32-bit variant of the Visual Studio toolchain to be present in PATH. The same for 64-bit. Remember to specify --arch=x86_mscoff when building 32-bit version. The architecture specification is mandatory as with the default architecture or --arch=x86 dub will try to use unsupported OPTLINK linker. OPTLINK linker requires unsupported version of libclang binaries. Remember to install LLVM to its default installation path and to add its binaries to the PATH environmental variable (otherwise you may need to change dub.json). When the program compiles under Windows but crashes at start, make sure an appropriate version of libclang.dll is available for DStep (you can validate it easily by copying dll to the directory with DStep). Here you can find more information on the topic.

Usage

$ dstep Foo.h -o Foo.d

For translating Objective-C headers add the -ObjC flag.

$ dstep Foo.h -o Foo.d -ObjC

For translating multiple files at once, simply pass all the files to dstep. In this case though, -o (if given) would point to output directory name. The directory will be created if it doesn't exist.

$ dstep Foo1.h Foo2.h Foo3.h .... FooN.h -o ./outputDirectory/

Use -h for usage information. Any flags recognized by Clang can be used.

API Notes

API Notes allows to transform the translated output in various ways, like renaming symbols, without having to modify the original headers. This is achieved by suppling a "sidecar" file to DStep. For more information, see the Clang documentation for API notes [1]. The API Notes format used by Clang is indented to be used to annotate API's for importing into Swift. DStep piggybacks and uses the same format, with some minor additions.

To use the API Notes feature, create a new file, api_notes.yml, with the following content:

Functions:
  - Name: foo
    SwiftName: bar

Assuming the input file, foo.h, has the following content:

void foo();

Run DStep with the following command:

dstep foo.h --api-notes api_notes.yml

The translated output will look as follows:

extern (C):

void bar ();

Member Functions

API Notes also supports converting free functions to instance methods. To convert a free function into an instance method, use the following syntax:

Functions:
  - Name: foo
    SwiftName: A.bar(this)

Where foo is the original name of the free function. A is the name of the struct which foo will be an instance method of. bar is the new new name of the instance method. this indicates the function should be an instance method.

Assuming the input file, foo.h, has the following content:

void foo(Foo foo);
int toInt(const char* str);

struct A {
  int b;
};

Run DStep with the following command:

dstep foo.h --api-notes api_notes.yml

The translated output will look as follows, the declaration of the struct A will be output in a separate file:

module foo;

extern (C):

int toInt (const char* str);

module A;

struct A {
    int b;

    void bar()
    {
        __foo(this);
    }

    extern (C) pragma(mangle, "foo") private static
    void __foo();
}

[1] https://clang.llvm.org/docs/APINotes.html

Limitations/Known issues

• Supports translating some of the preprocessor, like: #define for simple constants, function like macros and the token concatenation operator (##)
• Doesn't translate #include to import. Imports for a few standard C headers are added automatically
• Doesn't translate C++ at all
• Umbrella headers. Some headers just serve to include other headers. If these other headers contain some form of protection, like #error, to be included directly this can cause problems for DStep
• Some headers are designed to always be included together with other header files. These headers may very well use symbols from other header files without including them itself. Since DStep is designed to convert header files one-by-one this doesn't work. There are two workarounds for this:
  1. Add #include-directives for the header files the header file is actually using
  2. Use the -include <file> flag available in Clang to indicate the given <file> should be processed before the file that should be translated. DStep accepts all flags Clang accepts