compile-commands 2.0.1

Compilation Database Manipulation Utility

Compilation Database Manipulation Utility

This utility facilitates the use and modifications of compilation databases (CDB).
Modifying compilation databases can be useful especially when you don't have control over how a project is built.

Install

pip install compile-commands

Requirements

Requires at least python 3.8

Usage

This tool has many possible uses, some of them are listed below.

In a project composed of subproject with their own build directories, you can use --merge and indicate the root --dir and it will merge them. This is particularly useful for LSP servers that don't handle these projects well.

compile-commands --dir /path/to/project --merge

This may be slow if the project is big one alternative would to specify "by hand" the compilation databases with --files.

compile-commands --files $(fd compile_commands.json)
compile-commands --files myproject1/build/compile_commands.json myproject2/build/compile_commands.json --merge

The output file will named by default "compile_commands.json" in the current working directory. You can use -o, --output to override this behavior.

You can also indicate to a LSP server that you prefer using libc++ instead of libstdc++ even if your buildsystem doesn't use it.

compile-commands --file compile-commands.json \
                 --add_flags='-stdlib=libc++'

--add_flags takes in a string so you can add multiple flags easily

compile-commands --file compile-commands.json \
                 --add_flags='-stdlib=libc++ -O0'

You can combine --add_flags with --run to monitor warnings:

compile-commands --file compile-commands.json \
                 --add_flags='-Wall -Wextra -pedantic -fsyntax' \
                 --run --threads=12

You can decide to treat only a subset of your project by using --filter_files or --remove_files.
--filter_files takes in a regular expression whereas --remove_files takes in a comma-separated list of absolute paths.

You can as example filter out .c files from the database:

compile-commands --file compile-commands.json \
                 --filter_files='.*\.c$' \
                 --remove_files path/to/file1 path/to/file2

You can decide to treat only a subset of your project by using --include_files which takes in a comma-separated list of absolute paths. You can also prefix each paths passed to --include_files and --remove_files by using --path-prefix.

compile-commands --file compile-commands.json \
                 --include_files= path/to/file1 path/to/file2

You can use the -o flag to specify the name of the output file in case you don't want to overwrite

compile-commands --file compile-commands.json \
                 --filter_files='.c\$' \
                 -o my-db-without-c-files.json

You can also filter out parts of the commands based on a regular expression using --filter.
This is particularly useful when you need to modify the -o from the compiler's command. A good example of that is using ClangBuildAnalyzer.

mkdir ftime
cd ftime
compile-commands --file=/path/to/project/compile-commands.json \
                 --add_flags='-ftime-trace' \
                 --filter='-o .*\\.o' \
                 --run -j 12

# .json and .o files are created in-place!
ClangBuildAnalyzer --all . capture_file
ClangBuildAnalyzer --analyze capture_file

We add the clang's -ftime-trace as required by ClangBuildAnalyzer and remove every occurences of -o path/to/object/file.o and run each commands to produces the json tracings.
What if g++ was used during the creation of compilation database ? In this case we can use --clang and --gcc to switch between the two compilers and even change the path of the compiler with --compiler_path if let's say gcc is in /usr/bin and the clang we want to use is in /usr/bin/local.

compile-commands --file=/path/to/project/compile-commands.json \
                 --clang --compiler_path='/usr/bin/local' \
                 --add_flags='-ftime-trace' \
                 --filter='-o .*\\.o' \
                 --run -j 12 

--filter also accepts a replacement through the --replacement flag, it accepts reference to groups within the regular expression as per re.sub(). --filter is also useful to remove flags that are not compatible with both gcc and clang.

If you are a user of the Ninja buildsystem you might notice that the above example does not work. That is because generating a CDB through CMake using Ninja as the generator will result in having relative include paths within the CDB (relative to "directory" that is). This is inconvenient because the above effectively moves the build directory but does not move dependencies. To fix that you can use --absolute_include_directories which will modify relative includes paths into absolute include paths.