Building and hacking LDC on Windows using MSVC

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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 the GitHub CI release.


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 Azure Pipelines scripts for Ubuntu Linux and macOS and 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 x64 Native Tools Command Prompt for VS 2019 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 1.10.2;%~dp0Tools\make-4.2.1;C:\Program Files\Git\usr\bin;C:\Program Files\Git\bin;%~dp0Tools\cmake-3.19.4-win64-x64\bin;%~dp0Tools\Winpython64-\python-3.7.4.amd64;%PATH%
:: set D host compiler
set DMD=%~dp0ldc2-1.24.0-windows-multilib\bin\ldmd2.exe
:: set a few environment variables for dmd-testsuite
set OS=windows
set MODEL=64
if not exist "%TERM%" set TERM=msys
start /belownormal cmd.exe /k "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\VsDevCmd.bat" -arch=x64

Use -arch=x86 in the last line and set MODEL=32 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 link /version should display the banner from the MS linker.
  • 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.
  • For the tests:
    • Running make --version should display the banner from GNU make.
    • Starting a bash shell via bash and then invoking link /version should still display the MS linker banner. If it doesn't, make sure that git's usr\bin directory is listed before its bin directory in PATH.

Building LLVM

Building LLVM takes quite a while, so you may want to download a prebuilt version from here. We use these prebuilt packages for CI and the official release packages. Just extract the archive into C:\LDC\LLVM-x64 and then skip this section. In case you encounter errors wrt. unsupported command-line options or linking errors when building LDC, you probably use a different MSVC/clang toolchain version and will need to build LLVM yourself.

  • Download an LLVM source tarball (llvm-x.y.z.src.tar.xz). We maintain an LLVM fork with minimal modifications; vanilla LLVM can be used as well.
  • Extract it into C:\LDC (e.g., with 7-Zip), so that you end up with the source tree in e.g. C:\LDC\llvm-11.0.1.src.
  • cd C:\LDC
  • 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 ..\llvm-11.0.1.src

    Use -DCMAKE_BUILD_TYPE=Debug to build a debug version (and probably use -DLLVM_USE_CRT_DEBUG=MTd then). The LLVM page on CMake documents other variables you can change. For a 32-bit build, use -DLLVM_DEFAULT_TARGET_TRIPLE=i686-pc-windows-msvc.

  • Build LLVM: ninja
  • Install it (to C:\LDC\LLVM-x64): ninja install
  • Note that you'll need to keep the C:\LDC\build-llvm-x64 directory in order to keep the LLVM debuginfos (.pdb files) available.

Building LDC

  • cd C:\LDC
  • git clone --recursive
  • md build-ldc-x64
  • cd build-ldc-x64
  • Use a command like this (in one line) to create the Ninja build files:

    cmake -G Ninja ..\ldc

    You can specify the D host compiler explicitly by adding -DD_COMPILER=c:\path\to\ldmd2.exe.

  • Build LDC and the default libraries: ninja. The binaries end up in C:\LDC\build-ldc-x64\bin.
  • If you want to install it (to C:\LDC\LDC-x64): ninja install


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

Running the LDC D unit tests

  • cd C:\LDC\build-ldc-x64
  • ctest --output-on-failure -R ldc2-unittest

Running the LIT (LLVM Integrated Tester) tests

You'll need to have lit installed for Python:

  • Upgrade pip: python -m pip install -U pip
  • Install lit: python -m pip install lit
  • Make sure it works: python -c "import lit.main; lit.main.main();" --version .

To run the tests from your build dir you can do:

  • cd C:\LDC\build-ldc-x64
  • ctest -V -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 druntime/Phobos unit tests and druntime integration tests

  • Make sure the 64/32-bit libcurl.dll (bundled with LDC) can be found in a PATH directory. Verify by running where libcurl.dll.
  • cd C:\LDC\build-ldc-x64
  • Build the unit tests: ninja all-test-runners
  • Run the tests, excluding LDC unit tests, LIT tests and dmd-testsuite: ctest --output-on-failure -E "dmd-testsuite|lit-tests|ldc2-unittest"

Running the dmd-testsuite tests

  • If you haven't already, set the OS and MODEL environment variables:
    • set OS=windows (since v1.17, previously win{32,64})
    • set MODEL={32,64}
  • cd C:\LDC\build-ldc-x64
  • ctest -V -R dmd-testsuite
    • Debug only: ctest -V -R "build-run-dmd-testsuite|dmd-testsuite-debug"
    • Release only: ctest -V -R dmd-testsuite -E -debug

Developing/debugging LDC/LLVM with Visual Studio

Be sure to use Rainer's great Visual D plugin for VS.

  • 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 15 Win64" ...

This creates the VS 2017 solution C:\LDC\vs-ldc-x64\ldc.sln. A Visual Studio solution for LLVM can be created the same way.

I don't recommend building LDC/LLVM with VS directly; I only use VS for development/debugging and build in the shell with Ninja.

Windows MSVC