Paul and myself got trapped a few times by not seeing the effects of applying a patch to the nolibc source code until a "make clean" was issued in the nolibc directory. It's particularly annoying when trying to confirm that a proposed patch really solves a problem (or that reverting it reintroduces the problem).
The reason for the sysroot not being rebuilt was that it can be quite slow. But in fact it's only slow after a "make clean" issued at the kernel's topdir, because it's the main "make headers" that can take a tens of seconds; as long as "usr/include" still contains headers, the "headers_install" phase is only a quick "rsync", and rebuilding the whole nolibc sysroot takes a bit less than one second, which is perfectly acceptable for a test, even more once the time lost caused by misleading results if factored in.
This patch marks the sysroot target as phony and starts by clearing the previous sysroot for the current architecture before reinstalling it. Thanks to this, applying a patch to nolibc makes the effect immediately visible to "make nolibc-test":
$ time make -j -C tools/testing/selftests/nolibc nolibc-test make: Entering directory '/k/tools/testing/selftests/nolibc' MKDIR sysroot/x86/include make[1]: Entering directory '/k/tools/include/nolibc' make[2]: Entering directory '/k' make[2]: Leaving directory '/k' make[2]: Entering directory '/k' INSTALL /k/tools/testing/selftests/nolibc/sysroot/sysroot/include make[2]: Leaving directory '/k' make[1]: Leaving directory '/k/tools/include/nolibc' CC nolibc-test make: Leaving directory '/k/tools/testing/selftests/nolibc'
real 0m0.869s user 0m0.716s sys 0m0.149s
Cc: "Paul E. McKenney" paulmck@kernel.org Link: https://lore.kernel.org/all/20221021155645.GK5600@paulmck-ThinkPad-P17-Gen-1... Signed-off-by: Willy Tarreau w@1wt.eu --- tools/testing/selftests/nolibc/Makefile | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile index 69ea659caca9..22f1e1d73fa8 100644 --- a/tools/testing/selftests/nolibc/Makefile +++ b/tools/testing/selftests/nolibc/Makefile @@ -95,6 +95,7 @@ all: run sysroot: sysroot/$(ARCH)/include
sysroot/$(ARCH)/include: + $(Q)rm -rf sysroot/$(ARCH) sysroot/sysroot $(QUIET_MKDIR)mkdir -p sysroot $(Q)$(MAKE) -C ../../../include/nolibc ARCH=$(ARCH) OUTPUT=$(CURDIR)/sysroot/ headers_standalone $(Q)mv sysroot/sysroot sysroot/$(ARCH) @@ -133,3 +134,5 @@ clean: $(Q)rm -rf initramfs $(call QUIET_CLEAN, run.out) $(Q)rm -rf run.out + +.PHONY: sysroot/$(ARCH)/include