Clang tooling requires a compilation database to figure out the build options for each file. This enables tools like clang-tidy and clang-check. See https://clang.llvm.org/docs/HowToSetupToolingForLLVM.html for more information. Normally cmake is used to generate the compilation database, but the linux kernel uses make. Another option is using [BEAR](https://github.com/rizsotto/Bear) which instruments exec to find clang invocations and generate the database that way. Clang 4.0.0 added the -MJ option to generate the json for each compilation unit. https://reviews.llvm.org/D27140 This patch takes advantage of the -MJ option. So it only works for Clang. Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx> --- I have a couple TODOs in the code that I would like some feedback on. Specifically why extra-y doesn't seem to work in the root Makefile. Also, is there a way to add the correct list of prerequisites to the compile_commands.json target? Thanks, Raul Makefile | 20 ++++++++++++++++++++ lib/Kconfig.debug | 7 +++++++ scripts/Makefile.build | 9 ++++++++- 3 files changed, 35 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index a61a95b6b38f7..06067ee18ff64 100644 --- a/Makefile +++ b/Makefile @@ -1663,6 +1663,26 @@ quiet_cmd_tags = GEN $@ tags TAGS cscope gtags: FORCE $(call cmd,tags) +# Compilation Database +# --------------------------------------------------------------------------- +# Generates a compilation database that can be used with the LLVM tools +ifdef CONFIG_COMPILATION_DATABASE + +quiet_cmd_compilation_db = GEN $@ +cmd_compilation_db = (echo '['; \ + find "$(@D)" -mindepth 2 -iname '*.json' -print0 | xargs -0 cat; \ + echo ']') > "$(@D)/$(@F)" + +# Make sure the database is built when calling `make` without a target. +# TODO: Using extra-y doesn't seem to work. +_all: $(obj)/compile_commands.json + +# TODO: Is there a variable that contains all the object files created by +# cmd_cc_o_c? Depending on `all` is kind of a hack +$(obj)/compile_commands.json: all FORCE + $(call if_changed,compilation_db) +endif + # Scripts to check various things for consistency # --------------------------------------------------------------------------- diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index eae43952902eb..46fceb1fff3d9 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -238,6 +238,13 @@ config GDB_SCRIPTS instance. See Documentation/dev-tools/gdb-kernel-debugging.rst for further details. +config COMPILATION_DATABASE + bool "Generate a compilation database" + depends on CLANG_VERSION >= 40000 + help + This creates a JSON Compilation Database (compile_commands.json) + that is used by the clang tooling (clang-tidy, clang-check, etc). + config ENABLE_MUST_CHECK bool "Enable __must_check logic" default y diff --git a/scripts/Makefile.build b/scripts/Makefile.build index ae9cf740633e1..0017bf397292d 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -145,8 +145,15 @@ $(obj)/%.ll: $(src)/%.c FORCE # The C file is compiled and updated dependency information is generated. # (See cmd_cc_o_c + relevant part of rule_cc_o_c) +ifdef CONFIG_COMPILATION_DATABASE +# TODO: Should we store the json in a temp variable and only copy it to the +# final name when the content is different? In theory we could avoid having to +# generate the compilation db if the json did not change. +compdb_flags = -MJ $(@D)/.$(@F).json +endif + quiet_cmd_cc_o_c = CC $(quiet_modtag) $@ - cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $< + cmd_cc_o_c = $(CC) $(c_flags) $(compdb_flags) -c -o $@ $< ifdef CONFIG_MODVERSIONS # When module versioning is enabled the following steps are executed: -- 2.22.0.rc1.311.g5d7573a151-goog
