Building and hacking LDC on Windows using MSVC

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Revision as of 08:26, 30 August 2017 by Kinke (talk | contribs) (Build LLVM)
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Windows MSVC x86/x64 are first class targets for LDC. This page documents how to build, test and hack LDC2 on Windows.

LDC binaries

If you just want to download the very latest LDC binaries, head over to Latest LDC binaries for Windows.


It is hard for us to keep these wiki pages up-to-date. If you run into trouble, have a look at the build scripts for our Continuous Integration platforms: the files .travis.yml (Ubuntu Linux and OSX) and appveyor.yml (Windows) are always up-to-date with the latest build setup.

Building LDC

Required software

Shell environment

I use a little batch file to set up my LDC build environment. It's located in the root of my LDC environment: C:\LDC\shell.cmd. It sets up the PATH environment variable (I've installed the portable tools into C:\LDC\Tools) and then spawns a new VS 2015 x64 Native Tools Command Prompt with a below-normal process priority, so that my system stays responsive while building. I use a shortcut on my desktop to this batch file. Please adjust it to your needs (and note that %~dp0 is the directory containing the script, i.e., C:\LDC\).

@echo off
set PATH=%~dp0LDC-x64\bin;%~dp0LLVM-x64\bin;%~dp0Tools\Ninja 1.6.0;%~dp0Tools\PortableGit-\usr\bin;%~dp0Tools\PortableGit-\bin;%~dp0Tools\make-4.2.1;%~dp0Tools\cmake-3.3.0-win32-x86\bin;%~dp0Tools\WinPython-64bit-\python-2.7.13.amd64;%PATH%
set DMD=%~dp0dmd2\windows\bin\dmd.exe
if not exist "%TERM%" set TERM=msys
start /belownormal %comspec% /k "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" amd64

Use x86 instead of amd64 as argument to vcvarsall.bat if you want to build a 32-bit LDC.

Open a shell by executing the batch file.

  • Running cl should display the banner from the MS compiler.
  • Running git --version should display the banner from git.
  • Running python --version should display the banner from python.
  • Running cmake --version should display the banner from cmake.
  • Running ninja --version should display the ninja version.

Build LLVM

To build LLVM from the command line, just execute the following steps (from C:\LDC):

  • Get the source: git clone llvm
  • Branch release_40 (git checkout release_40) is currently recommended.
  • Create a build directory: md build-llvm-x64
  • Change into it: cd build-llvm-x64
  • Use a command like this (in one line) to create the Ninja build files:

    cmake -G Ninja -DCMAKE_INSTALL_PREFIX="C:\LDC\LLVM-x64"

    Omit the CMAKE_BUILD_TYPE definition to build a debug version. The LLVM page on CMake documents other variables you can change. The most common is to add more targets. E.g. to build a target for ARM you change the targets to build to -DLLVM_TARGETS_TO_BUILD=X86;ARM.

  • Build LLVM: ninja
  • Install it: ninja install

Build libconfig (only required for LDC < 1.3)

Latest confirmed working revision: 7585cf6. Feel free to try the latest version, if it fails you can fall back on this one.

  • cd C:\LDC
  • git clone libconfig
  • cd libconfig
  • git checkout 7585cf6
  • Build the static C library: msbuild lib\libconfig.vcxproj /t:Rebuild /p:Configuration=ReleaseStatic /p:Platform=x64
    • Use configuration DebugStatic for debug LDC builds to ensure we link against the same runtime library

Build LDC

  • cd C:\LDC
  • git clone --recursive git:// ldc
  • md build-ldc-x64
  • cd build-ldc-x64
  • Set environment variable to which D compiler should be used to build LDC:

    set DMD=c:\path\to\dmd\bin\dmd.exe
  • Use a command like this (in one line), omitting the variables starting with LIBCONFIG when building LDC ≥ 1.3:

          -DLLVM_ROOT_DIR="C:/LDC/LLVM-x64" -DLIBCONFIG_INCLUDE_DIR="C:/LDC/libconfig/lib"
          -DLIBCONFIG_LIBRARY="C:/LDC/libconfig/lib/x64/ReleaseStatic/libconfig.lib" ..\ldc
  • Build LDC and the runtimes: ninja
  • If you want to install it: ninja install


Running the LIT-based tests

You'll need to have lit installed for Python. To run the tests from your build dir you can do:

  • cd C:\LDC\build-ldc-x64
  • ctest --output-on-failure -R lit-tests

or you can go to the tests folder inside your build dir, and run the script.

  • cd C:\LDC\build-ldc-x64\tests
  • python -v .

The second way is convenient for running individual tests:

  • python -v codegen/align.d

Running the runtime unit tests

  • cd C:\LDC\build-ldc-x64
  • Build the unit tests: ninja druntime-ldc-unittest druntime-ldc-unittest-debug phobos2-ldc-unittest phobos2-ldc-unittest-debug
  • Run the tests, excluding dmd-testsuite and the LIT tests: ctest --output-on-failure -E "dmd-testsuite|lit-tests"

For troubleshooting be sure to examine the file C:\LDC\build-ldc-x64\Testing\Temporary\LastTest.log.

Running the dmd-testsuite tests

dmd-testsuite requires a minimalistic GNU environment. bash and a lot of GNU utilities are shipped with git. Additionally, we need GNU make.

  • Either build GNU make from source yourself (they ship with a Visual Studio solution) or download this pre-built one (v4.2.1).
  • Edit your shell batch script and add the directory containing your make.exe to your PATH, e.g., set PATH=%~dp0Tools\make;%PATH%
  • Spawn a new shell and make sure make --version prints its banner.

Now that we have extended our LDC build environment, we're able to run the dmd-testsuite tests:

  • cd C:\LDC\build-ldc-x64
  • Set some environment variables for dmd-testsuite's Makefile:
    • OS
      • 32-bit: set OS=Win_32
      • 64-bit: set OS=Win_64
    • DMD_TESTSUITE_MAKE_ARGS enables parallel execution, e.g.
  • ctest -V -R dmd-testsuite
    • Debug only: ctest -V -R dmd-testsuite-debug
    • Release only: ctest -V -R dmd-testsuite -E -debug

Developing/debugging LDC/LLVM with Visual Studio

  • cd C:\LDC
  • md vs-ldc-x64
  • cd vs-ldc-x64
  • Use the cmake command from the Build LDC section, but use the VS generator instead of Ninja this time: cmake -G "Visual Studio 14 Win64" ...

This creates the VS 2015 solution C:\LDC\vs-ldc-x64\ldc.sln. A Visual Studio solution for LLVM can be created the same way.


The simple D program hello.d

import std.stdio;

int main()
    writefln("Hello LDC2");
    return 0;

can be compiled and linked with the commands:

ldc2 -c hello.d
ldc2 hello.obj

or simply with: ldc2 hello.d