Theia - Cpp Extension
This extension uses Clangd to provide LSP features.
To install Clangd on Ubuntu 18.04:
$ wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
$ echo "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main" | sudo tee /etc/apt/sources.list.d/llvm.list
$ sudo apt-get update && sudo apt-get install -y clangd
See here for detailed installation instructions.
Getting accurate diagnostics
To get accurate diagnostics, it helps to:
- Have the build system of the C/C++ project generate a
compile_commands.json
file. - Point Clangd to the build directory containing said
compile_commands.json
.
Step #2 can be done using the cpp.buildConfigurations
preference. In your
home or your project .theia/settings.json
, define one or more build
configurations:
{
"cpp.buildConfigurations": [{
"name": "Release",
"directory": "/path/to/my/release/build"
},{
"name": "Debug",
"directory": "/path/to/my/debug/build"
}]
}
You can then select an active configuration using the C/C++: Change Build Configuration
command from the command palette.
Setting clangd executable path and arguments
The path of the clangd executable to use can be specified by either:
-
Setting the
CPP_CLANGD_COMMAND
environment variable -
Setting the
cpp.clangdExecutable
preference in your home or your project.theia/settings.json
:{ "cpp.clangdExecutable": "/path/to/my/clangd/executable" }
-
Adding clangd to system path. Default value of executable path is set to
clangd
Similarly, the command-line arguments passed to clangd can be specified by either:
-
Setting the
CPP_CLANGD_ARGS
environment variable -
Setting the
cpp.clangdArgs
preference in your home or your project.theia/settings.json
:{ "cpp.clangdArgs": "list of clangd arguments" }
Getting cross-file references to work
You may notice that by default, cross-references across source file boundaries
don't work. For example, doing a "Go To Definition" on a function defined in a
different source file (different .c
or .cpp
) doesn't work, instead it sends
you to the declaration of the function, typically in a header file.
To get this working, you need to enable clangd's global index using the
--background-index
command-line argument.
{
"cpp.clangdArgs": "--background-index"
}
Using the clang-tidy linter
Note: This functionality is available when using clangd 9 and later.
You can set the preference 'cpp.clangTidy' to enable the clang-tidy linter included in clangd. When the preference is enabled, there are two ways to choose which of its built-in checks clang-tidy will use:
- using the preferences: 'cpp.clangTidyChecks'
- using the file '.clang-tidy' . This file is located in the same folder of the files or a parent folder.
Note: When the preference setting for "cpp.clangTidyChecks" is set, the configs will be merged with the configuration found in the ".clang-tidy" file. If you want to drop the configs from ".clang-tidy", you'd need to disable it in "cpp.clangTidyChecks" with "cpp.clangTidyChecks": "-*".
The syntax used to fill the checks can be found at http://clang.llvm.org/extra/clang-tidy/
clang-tidy has its own checks and can also run Clang static analyzer checks. Each check has a name (see link above for full list). Clang-tidy takes as input the checks that should run, in the form of a comma-separated list of positive and negative (prefixed with -) globs. Positive globs add subsets of checks, negative globs remove them.
There are two ways to configure clang-tidy's checks: through a Theia preference or using a .clang-tidy config file. Here are examples for both:"
- for the preferences: "cpp.clangTidyChecks": "*,-readability-*"
- Meaning: enables all list-checks and disable all readability-* checks
- for the .clang-tidy file: Checks: "-*,readability-*"
- Meaning: disable all list-checks and enable all readability-* checks
Running clang-tidy as a task
To be able to run clang-tidy as a task, you need to install the program.
UNIX
sudo apt-get install clang-tidy
Note: not all operating system are currently supported with this linter yet.
The clang-tidy task will read the "checks" and other configuration fields from the ".clang-tidy" file located in the closest parent directory of the source file.
P.S. You do not need to provide a value for each field.
Those configurations fields can be:
Checks
CheckOptions
FormatStyle
HeaderFilterRegex
User
WarningsAsErrors
You can run the following command to have an idea of the fields found in file ".clang-tidy"
clang-tidy -dump-config
In .theia/tasks.json, add the following:
{
"label": "[Task] clang-tidy",
"type": "shell",
"cwd": "${workspaceFolder}",
"command": "clang-tidy",
"args": [
"*"
],
"options": {},
"problemMatcher": [
"$clangTidyMatcher"
]
}
If you want a description for each task field, see theia/packages/task/src/browser/task-schema-updater.ts
When there is no compilation database, clang-tidy could run but you may need to be more specific which files to select. One way is to replace the "args" from the "*" to
"**/*.cpp" to only parse files with the "cpp" extension or
"**/*.c" to parse the "c" files extension.