assarbad/msvc-undoc

Undocumented MSVC

Undocumented MSVC

• link.exe

Environment variables

• LOG_BUILD_COMMANDLINES, see below.

Used internally (requiring further research)

• MSC_CMD_FLAGS

Findings by others

• Geoff Chappell's seminal studies about Microsoft Visual C++, they aged well. Some of the findings he gives are still valid, some command line switches have meanwhile been documented.
• Someone going by the moniker @adeyblue found out about LOG_BUILD_COMMANDLINES ten years before I did
• The Chromium build appears to use plenty of flags, some of which are not documented
• Microsoft Visual C/C++, Visual Studio tips and tricks
• Boost-MSBuild
• MSVC hidden flags (unfortunately not much "meat")

Additional resources

• Versions of Visual C++ and the _MSC_VER and _MSC_FULL_VER values for various versions documented (archived)
  • BSD-2-Clause-licensed project to read the values from binaries created with MSVC (can be suppressed via /emittoolversioninfo:no to the link.exe)
• The mysterious 'Rich' header (archived)
  • Article by Daniel Pistelli
• Performance-related resources
  • Visual Studio 2017 Throughput Improvements and Advice
  • Finding build bottlenecks with C++ Build Insights
  • C++ build throughput investigation and tune up
  • Best unknown MSVC flag: d2cgsummary
  • Another cool MSVC flag: /d1reportTime
• Deterministic builds:
  • Why are the module timestamps in Windows 10 so nonsensical?
  • The Chromium Projects: Deterministic builds
  • reproducible-builds.org

Useful tips

Use LOG_BUILD_COMMANDLINES to log build command lines

Ever wondered what command lines get effectively executed "behind" those response files used by Visual Studio and MSBuild?

LOG_BUILD_COMMANDLINES has the answer. The environment variable should be set to a file path, which will be a plain text log file receiving all those build command lines. This works even for those command lines that actually end up being invoked using response files due to command line length limitations on Windows.

The following Directory.Build.props provides a simple example of how to use this method. It uses the SetEnv MSBuild target to ensure that the environment variable gets set prior to invocation of the tools that honor the presence of this variable.

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="Current" xmlns="http://schemas.microsoft.com/developer/msbuild/2003" InitialTargets="LogBuild">
	<PropertyGroup>
		<ThisProjectBuildLogFileName Condition="'$(MSBuildProjectName)' == ''">$(MSBuildThisFileDirectory)BuildCommandLines.log</ThisProjectBuildLogFileName>
		<ThisProjectBuildLogFileName Condition="'$(MSBuildProjectName)' != ''">$(MSBuildThisFileDirectory)BuildCommandLines-$(MSBuildProjectName).log</ThisProjectBuildLogFileName>
	</PropertyGroup>
	<Target Name="LogBuild" BeforeTargets="SetUserMacroEnvironmentVariables;SetBuildDefaultEnvironmentVariables">
		<Message Text="Setting LOG_BUILD_COMMANDLINES='$(ThisProjectBuildLogFileName)'" />
		<SetEnv Name="LOG_BUILD_COMMANDLINES" Value="$(ThisProjectBuildLogFileName)" Prefix="false" />
	</Target>
</Project>

ETW-related GUIDs

• GUID_MSVC_PROVIDER: {9C642431-C036-7958-4B0E-FE163528322B}