linux/tools/build
Brian Norris ea974028a0 tools build: Avoid circular .fixdep-in.o.cmd issues
The 'fixdep' tool is used to post-process dependency files for various
reasons, and it runs after every object file generation command. This
even includes 'fixdep' itself.

In Kbuild, this isn't actually a problem, because it uses a single
command to generate fixdep (a compile-and-link command on fixdep.c), and
afterward runs the fixdep command on the accompanying .fixdep.cmd file.

In tools/ builds (which notably is maintained separately from Kbuild),
fixdep is generated in several phases:

 1. fixdep.c -> fixdep-in.o
 2. fixdep-in.o -> fixdep

Thus, fixdep is not available in the post-processing for step 1, and
instead, we generate .cmd files that look like:

  ## from tools/objtool/libsubcmd/.fixdep.o.cmd
  # cannot find fixdep (/path/to/linux/tools/objtool/libsubcmd//fixdep)
  [...]

These invalid .cmd files are benign in some respects, but cause problems
in others (such as the linked reports).

Because the tools/ build system is rather complicated in its own right
(and pointedly different than Kbuild), I choose to simply open-code the
rule for building fixdep, and avoid the recursive-make indirection that
produces the problem in the first place.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Link: https://lore.kernel.org/all/Zk-C5Eg84yt6_nml@google.com/
Link: https://lore.kernel.org/r/20240715203325.3832977-3-briannorris@chromium.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2024-08-05 12:09:14 -03:00
..
Documentation tools build: Add CFLAGS_REMOVE_* support 2016-11-14 11:37:25 -03:00
feature Another perf tools fixes for v6.11 2024-07-30 19:22:41 -07:00
tests License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
Build.include tools build: Enable warnings through HOSTCFLAGS 2021-12-07 22:18:23 -03:00
fixdep.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile tools build: Avoid circular .fixdep-in.o.cmd issues 2024-08-05 12:09:14 -03:00
Makefile.build tools/build: Fix -s detection code in tools/build/Makefile.build 2023-10-18 15:29:35 -07:00
Makefile.feature tools: Make pkg-config dependency checks usable by other tools 2024-07-17 13:14:35 -07:00
Makefile.include treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00