On Fri, Jun 7, 2019 at 5:30 AM Raul E Rangel <rrangel@xxxxxxxxxxxx> wrote: > > 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)" Using 'find' has the same problem as scripts/gen_compile_commands.py does. Unless we start build from the clean source tree, compile_commands.json will contain stale entries from the previous building. The motivation is to replace scripts/gen_compile_commands.py entirely? Generally, we do not need two ways to do the same thing... > +# 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 > -- Best Regards Masahiro Yamada
