MSBuild compile_commands.json logger

This is a simple MSBuild logger that emits a Clang-style compile_commands.json file by observing the MSVC compiler invocations when a C++ project is built. It is particularly useful with Visual Studio Code's C/C++ extension, which can be configured to use compile_commands.json to determine the compiler options (include paths, defines, etc.) for accurate IntelliSense.

Usage

Building the project is straightforward:

dotnet build

Then, invoke MSBuild with the -logger option. For example:

msbuild -logger:/path/to/CompileCommandsJson.dll MyProject

By default, compile_commands.json is written in the current directory. You can control the output path using a parameter, e.g.:

msbuild -logger:/path/to/CompileCommandsJson.dll;my_new_compile_commands.json MyProject

Limitations

There are two significant design limitations:

1. The logger will only emit entries for compiler invocations that it observes during a build; in particular, for an incremental build, there will be no output for any targets that are considered up to date.

2. The logger truncates the JSON file at startup, and writes to it incrementally throughout the build.

Thus, for an accurate result you should use this logger only on a completely clean build, and to avoid confusing tools (such as VSCode) that may observe the file as it is written, you should probably write the output to a temporary file and rename it only after the build succeeds. Typical usage is roughly:

rm -r out
msbuild -logger:CompileCommandsLogger.dll;cctmp.json
mv cctmp.json compile_commands.json

Author

Andrew Baumann