LDC

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Compilers: Overview — DMD — GDC — LDC ✎

The LDC project aims to provide a portable D programming language compiler with modern optimization and code generation capabilities. The compiler uses the official DMD frontend to support the latest D2 version and relies on the LLVM Core libraries for code generation.

LDC is fully Open Source; the parts of the code not taken/adapted from other projects are BSD-licensed (see the LICENSE file for details).

D1 is no longer supported in the current development tree; the last version supporting it can be found at the d1 Git branch.

Getting started

Project status

In general, LDC should work fine on most x86/x86-64 Unix-like systems, including Linux, OS X 10.7+ and most BSD flavors. Code generation should work for other platforms supported by the LLVM MC codegen infrastructure (for example ARM), but druntime/Phobos support will most likely be lacking.

OS X version prior to 10.7 (Lion) are currently not supported by the D2 compiler, because LLVM's support for thread-local storage depends on functionality which first appeared in 10.7.

x86 Windows using MinGW

  • LDC 2 from Git master compiles and builds druntime/Phobos, but requires applying patches to LLVM and the MinGW runtime to fix some bugs. See Building LDC on MinGW x86.
  • Hello World-style programs work (including TLS and exception handling).
  • A small number of remaining test cases still fails, but many of the harder issues (real math precision, MS C runtime-caused problems, ABI differences) have already been solved.
  • Estimate for making Windows x86/MinGW a »first class« target: 1 weekend of focused work, plus a Windows CI slave.

x86-64 Windows using MSVC

  • LDC/LDC2 from master branch compiles without patches.
  • See Building and hacking LDC on Windows using MSVC for detailed instructions.
  • LLVM 3.1 is required (3.0 does not work because of missing TLS support); LLVM 3.2/3.3 is preferred.
  • druntime and Phobos compile but linker errors are still possible.
  • Exception handling still needs work. You have to use LLVM 3.4 head and this patch to LLVM.
  • Contact: kai@redstar.de

ARM

  • Code generation is known to work.
  • Currently affected by PR15293, but a proper implementation of the C ABI will be required anyway (similar to x86_64, see Clang source for test cases).
  • Some initial work has been done on druntime, but support is not yet complete – see issue #116.

PowerPC 64-bit

  • Requires LLVM trunk because of PR14751, PR14779, PR15347, PR15359, PR15630 and PR15632. A solution for PR15580 is currently missing (blocks linking of Dwarf debug symbols).
  • Only Linux because LLVM does not cleanly compile on AIX.
  • Code generation is known to work.
  • Issues in druntime and phobos:
    • druntime: Compiles cleanly with this patch applied
    • phobos: Compiles cleanly with this patch applied
    • Most of these changes are already passed as upstream pull requests
  • 95% of the test suite passes - only 54 tests (out of 1036) fail. These are some modules with problems (incomplete):
    • Unit test failures: core.math (math precision), core.thread (fiber implementation only), std.complex, std.bitmanip (release only with -O2/-O3), std.outbuffer, std.csv, std.math, std.getopt (math precision), std.regex (endian), ...
    • Seg faults: std.datetime, std.range, ...
    • Reason for failures are likely: math precision, thread synchronisation, frontend bugs, endian issues, bad code generation, ...
  • Linux/PPC64 specific implementations are missing: core.cpuid, std.internal.math.bigintppc64, ...
  • Contact: kai@redstar.de

Contributing

LDC is an entirely community-driven effort, so all contributions are warmly welcomed. The easiest way to help with development is to write high-quality bug reports for any issues you run into. For a quick guide on what a useful report should contain, please see Reporting LDC issues.

If you are interested in getting into compiler development, anecdotal evidence suggests that hacking on LDC might be a nice first step, particularly because the LLVM backend is very comfortable to work with. To get started, just browse through the issue list, find a ticket that tickles your fancy (some of them are specifically marked as "junior jobs"), and work on a fix – and of course don't hesitate to ask for advice at the mailing list or on IRC. An LDC contributor's guide is in the works.

We would also be excited to see LDC packages in more OS distributions, particular Debian and its derivatives. So, if you think you might be able to help, please just drop us a line at the development mailing list. We will actively try to make packaging as smooth as possible, but besides the fact that upstream-maintained packages are sometimes discouraged, it is hard to build good packages for a system you don't know well, so we need to rely on external contributors here.

Useful Links

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