# Windows support

LLD supports Windows operating system. When invoked as `lld-link.exe` or with `-flavor link`, the driver for Windows operating system is used to parse command line options, and it drives further linking processes. LLD accepts almost all command line options that the linker shipped with Microsoft Visual C++ (link.exe) supports.

The current status is that LLD is used to link production builds of large real-world binaries such as Firefox and Chromium.

## Development status

Driver

  Mostly done. Some exotic command line options that are not usually used for application development, such as `/DRIVER`, are not supported.

Linking against DLL

  Done. LLD can read import libraries needed to link against DLL. Both export-by-name and export-by-ordinal are supported.

Linking against static library

  Done. The format of static library (.lib) on Windows is actually the same as on Unix (.a). LLD can read it.

Creating DLL

  Done. LLD creates a DLL if `/DLL` option is given. Exported functions can be specified either via command line (`/EXPORT`) or via module-definition file (.def). Both export-by-name and export-by-ordinal are supported.

Windows resource files support

  Done. If an `.res` file is given, LLD converts the file to a COFF file using LLVM’s Object library.

Safe Structured Exception Handler (SEH)

  Done for both x86 and x64.

Module-definition file

  Partially done. LLD currently recognizes these directives: `EXPORTS`, `HEAPSIZE`, `STACKSIZE`, `NAME`, and `VERSION`.

Debug info

  Done. LLD can emit PDBs that are at parity with those generated by link.exe. However, LLD does not support /DEBUG:FASTLINK.

## Downloading LLD

The Windows version of LLD is included in the pre-built binaries of LLVM’s releases and in the LLVM Snapshot Builds.

## Building LLD

### Using Visual Studio IDE/MSBuild

1. Check out LLVM and LLD from the LLVM SVN repository (or Git mirror),

2. run `cmake -G "Visual Studio 12" <llvm-source-dir>` from VS command prompt,

3. open LLVM.sln with Visual Studio, and

4. build `lld` target in `lld executables` folder

Alternatively, you can use msbuild if you don’t like to work in an IDE:

    msbuild LLVM.sln /m /target:"lld executables\lld"

MSBuild.exe had been shipped as a component of the .NET framework, but since 2013 it’s part of Visual Studio. You can find it at “C:\Program Files (x86)\msbuild”.

You can build LLD as a 64-bit application. To do that, open VS2013 x64 command prompt and run cmake for “Visual Studio 12 Win64” target.

### Using Ninja

1. Check out LLVM and LLD from the LLVM SVN repository (or Git mirror),

2. run `cmake -G ninja <llvm-source-dir>` from VS command prompt,

3. run `ninja lld`

## Extensions

### LLD flags

- `/build-id`: Always generate GUID hash. When PDB is generated, LLD uses PDB content hash for GUID. Otherwise, LLD uses output binary content hash for GUID. LLD also provides `__buildid` symbol pointing to the 16 bytes GUID hash if there is a reference to it.