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cdtcloud-clangd-contexts-ext

Overview

An example application of the Clangd Contexts API, in the form of a simple VS Code extension. The extension maps the context concept of the API onto the notion of build configuration (or build target) familiar from IDEs such as Apple Xcode or Eclipse CDT.

Features

  • quickly and easily apply clangd contexts described by compile_commands.json files to projects in the workspace
  • configure clangd's invocation of clang to suppress GCC flags such as -fstack-usage that are not recognized by clang

How to Run the Example VS Code Extension

The most convenient way to run the extension with debugger support for stepping through the code is via the Launch Clangd Contexts Example Extension launch configuration in VS Code. The run-time workbench then provides

  • a build configuration selection widget in the status line
  • a context menu action on folders in the Explorer view to configure GCC flags to suppress in the clangd configuration

The launch configuration opens a VS Code run-time workbench on the example workspace (see below).

Alternatively, the extension is built and packaged also in the browser and Electron example applications. These example apps can be launched on the clangd contexts example workspace as follows:

# for the clangd example workspace opened in the browser
$ yarn start:browser:clangd
# for the clangd example workspace opened in the Electron deployment
$ yarn start:electron:clangd

Using the Example VS Code Extension

The example workspace contains two projects, app/ and lib/. If we have a look at the app/main.c file we can see a compilation error because the reference to a name defined in the lib/ project cannot be resolved. To fix this a build configuration needs to be set.

Note that until the example workspace has first been built according to these instructions, VS Code will not be able to show any build configurations to choose because the context directories containing the requisite makefiles and compilation databases do not yet exist.

This can be done via the command palette using the Clangd: Change build configuration command. Alternatively, the build configuration can be configured by clicking on the build configuration item on the status bar.

Note that the Clangd: Change build configuration command also restarts the clangd language server to apply the configuration changes. Some errors regarding rejected promises may be thrown by restarting the language server. However, they are harmless and can safely be ignored.

Clangd uses a dedicated cache per build configuration index, which means that switching between configurations does not require a full re-indexing.

The Debug_x86-64 configuration uses a GCC-specific compile flag which is not recognized by clangd. To avoid errors related to unsupported GCC compile flags the Clangd: Suppress unsupported GCC flags" command can be used. It is also possible to suppress GCC flags only in a specific subdirectory. Simply select the directory in the file explorer, open the context menu and select Clangd: Suppress unsupported GCC flags". The cdtcloud-clangd-contexts-ext extension then recursively collects all .clangd configuration files that are located within the workspace or within the selected directory and adds a configuration option that tells the clangd server to suppress the unsupported compilation flags.

Example Workspaces

  • examples/clangd-workspace
    • provides a small example workspace with two interrelated projects in which to test-drive the Clangd Contexts API via the extension

License