# VC-LTL - An elegant way to compile lighter binaries.

• 简体中文

I would like to turn into a stone bridge, go through 500 years of wind, 500 years of Sun, rain for 500 years, but she walked off a bridge!

1. About VC-LTL

VC-LTL is an open source CRT library based on the MS VCRT that reduce program binary size and say goodbye to Microsoft runtime DLLs, such as msvcr120.dll, api-ms-win-crt-time-l1-1-0.dll and other dependencies.

VC-LTL was originally a dedicated Dism++ runtime and was isolated and open sourced from Dism++ source code on Mar 6, 2017.

There are plenty of modules in large projects. If all binaries uses static compilation, it will use plenty of disk space and finally may crashed because of the fiber local storage (FLS) limitation.

But the VC-LTL can make your project using the built-in msvcrt.dll in the Windows. It solves the C runtime deployment problem and the fiber local storage (FLS) limitation problem effectively, and greatly reduce the binaries size. What a handy library!

Everyone can use it for free, even for the commerical use. Of course, I hope that if you mentioned the VC-LTL in your project, because I want to help more people.

• QQ Group: 633710173

1.1. The principle of VC-LTL

After using the VC-LTL, the binaries will be dynamically linked to the built-in msvcrt.dll or ucrtbase.dll in the Windows to reduce the binaries size. It is generally available if you use the VC-LTL in the project using the C Runtime, STL or MFC.

After using the VC-LTL, the size of the binaries will reduce about 30% if compiled from the C++ source code, and about 50% if compiled from the pure C source code.

1.2. Highlight

• 晚起的鸟儿也有虫虫吃，优雅的引用方式，仅添加一个属性表就能享受极致的体积体验。
• 无缝使用最新C/C++库以及最新编译器，尽情的使用最新规范。神马异常流防护（guard:cf）、静态对象线程安全初始化（threadSafeInit）……统统放马过来吧！！
• 拥有比微软原版更好的兼容性，即使想兼容Windows XP RTM也可以安心的对新编译器说“Yes”。
• 完全的开放代码，广泛的接受用户意见，希望大家能踊跃的 pull requests，为VC-LTL添砖加瓦。

Let's say goodbye to the Visual Studio 2008.

2. VC-LTL Compatibility

2.1. ABI Compatibility

Starting from VC-LTL 5.0, ABI is compatible with Microsoft. You can link use the static library with VC-LTL without recompiling!

In addition, in order to provide consistency in behavior, a Debug version of the library is also provided. It will still use msvcrt.dll or ucrtbase.dll, but it does not support the heap debugging functions. If you need to use the heap debugging, please disable VC-LTL.

2.2. Supported Visual Studio Versions

• Visual Studio 2015 (Support Clang with Microsoft CodeGen, Clang 3.7 with Microsoft CodeGen, Clang-LLVM)
• Visual Studio 2017 (Support Clang with Microsoft CodeGen, Clang-LLVM)
• Visual Studio 2019 (Support Clang-LLVM)
• Visual Studio 2022

2.3. Supported Build Tools

2.4. Supported Windows Versions

Tips: If you need to compile Windows XP compatible app (5.1.2600.0/5.2.3790.0), please don't forget to used YY-Thunks.

The binaries compiled with the VC-LTL is compatible with Windows XP and later, even in the environment which installed no hotfixes.

3. How to used?

We will enter the theme, we have prepared a rich VC-LTL Samples for your reference, and welcome to join our QQ group (633710173).

3.1. Using VC-LTL in Visual Studio

3.1.1. Choose reference mode

3.1.1.1. Reference via NuGet (recommend)

Right-click on the project and select "Manage NuGet Packages", then search for VC-LTL and choose the version that suits you, and finally click Install.

3.1.1.2. Reference via Registry

If you download and unzip VC-LTL Binary to D:\Src\VC-LTL, please double-click D:\Src\VC-LTL\Install.cmd.

The script will save the information in the registry HKCU\Code\VC-LTL.

Copy VC-LTL helper for Visual Studio.props to your project, then open the Property Manager ( View - Property Manager ) and right-click on the Release Configuration, click on Add Existing Property Sheet..., and finally select VC-LTL helper for Visual Studio.props.

3.1.2. Configure Project Properties

• C/C++ - Code Generation -Runtime Library adjust to Multi-threaded (/MT)

For XP support, please Right click on the project, Properties - NuGet Packages Settings - VC-LTL - Target CRT version - "msvcrt 5.1.2600.0". In addition, it is recommended that you install YY-Thunks.

3.2. Using VC-LTL in CMake

If you download and unzip VC-LTL Binary to D:\Src\VC-LTL, please double-click D:\Src\VC-LTL\Install.cmd.

The script will save the information in the registry HKCU\Code\VC-LTL.

3.2.1. Add VC-LTL Module File

Copy VC-LTL helper for cmake.cmake to your project. Then add include("VC-LTL helper for cmake.cmake") to CMakeLists.txt.

Example:

cmake_minimum_required(VERSION 3.5.2)
project(ltltest)

include("VC-LTL helper for cmake.cmake")

add_subdirectory(src)

3.2.2. Modify The Configuration

It's recommended to use /MT to compile the project when using VC-LTL. For XP support, please modify VC-LTL helper for cmake.cmake to enable set(WindowsTargetPlatformMinVersion "5.1.2600.0"). In addition, it is recommended that you install YY-Thunks.

3.3. Using VC-LTL in NMake/CL

3.3.1. Run VC-LTL Cmd Script

If you download and unzip VC-LTL Binary to D:\Src\VC-LTL, please double-click D:\Src\VC-LTL\Install.cmd.

The script will save the information in the registry HKCU\Code\VC-LTL.

Copy VC-LTL helper for nmake.cmd to your project. Run vcvars32.bat or vcvars64.bat and execute this script. The script will automatically modify the include and lib environment variables.

Example: cmd

call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"
call "D:\VC-LTL\VC-LTL helper for nmake.cmd"

nmake /f Test.mak

Example: powershell

$BuiltInVsWhereExe = "${env:ProgramFiles(x86)}\Microsoft Visual Studio\Installer\vswhere.exe"
$LatestVisualStudioRoot = & $BuiltInVsWhereExe -latest -prerelease -property installationPath

# x86、amd64、arm、arm64
& "$LatestVisualStudioRoot\Common7\Tools\Launch-VsDevShell.ps1" -arch x86
& D:\VC-LTL\VC-LTL helper for nmake.ps1"

& nmake /f Test.mak

3.3.2. Modify The Configuration

It's recommended to use /MT to compile the project when using VC-LTL. For XP support, please modify VC-LTL helper for nmake.cmd to enable set WindowsTargetPlatformMinVersion=5.1.2600.0. In addition, it is recommended that you install YY-Thunks.

3.4. Rebuild

Is the file size smaller? If you fail to compile, please refer to 4. FAQ. You can also feedback and work together to improve VC-LTL.

It is recommended to use /MT to compile when compiling with VC-LTL 5.0, and the dependent static libraries does not need to be recompiled.

4. FAQ

4.1. 未共享到msvcrt.dll/ucrtbase.dll

Cause

未正确引用VC-LTL。建议看看链接日志，是否链接了VC-LTL的lib。

Workaround

1：请务必确保 VC-LTL helper for Visual Studio.props 已经添加到工程。

2：确保以下设置正确：

• VC++ 目录 - 包含目录 - 【√ 从父项或项目默认设置继承(I)】
• VC++ 目录 - 库目录 - 【√ 从父项或项目默认设置继承(I)】

5. Known Issues

• Bug 22, VC-LTL的Debug模式不支持堆调试功能也无法使用ASAN
  • 如果您需要使用这些功能，可以针对Debug配置关闭VC-LTL。
• Bug 60, msvcrt模式下locale相关函数（如setlocale、std::locale）无法指定为区域为 .utf8
  • 如果需求如此必须使用，建议使用VC-LTL的UCRT模式（使用后将依赖ucrtbase.dll），如果不想依赖DLL就直接静态链接微软原版CRT吧。

Excursus - Third Party Licenses

• Visual Studio
• Microsoft.Windows.SDK.CRTSource