Hi,
This fixes a couple of minor aggravating factors that I ran across while trying to do some changes in selftests/vm. These are simple things, but like most things with GNU Make, it's rarely obvious what's wrong until you understand *the entire Makefile and all of its includes*.
So while there is, of course, joy in learning those details, I thought I'd fix these little things, so as to allow others to skip out on the Joy if they so choose. :)
First of all, if you have an item (let's choose userfaultfd for an example) that fails to build, you might do this:
$ make -j32
# ...you observe a failed item in the threaded output
# OK, let's get a closer look
$ make # ...but now the build quietly "succeeds".
That's what Patch 0001 fixes.
Second, if you instead attempt this approach for your closer look (a casual mistake, as it's not supported):
$ make userfaultfd
# ...userfaultfd fails to link, due to incomplete LDLIBS
That's what Patch 0002 fixes.
John Hubbard (2): selftests/vm: fix false build success on the second and later attempts selftests/vm: fix incorrect gcc invocation in some cases
tools/testing/selftests/vm/Makefile | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
If one or more of these selftest fail to build, then after the first failure, subsequent invocations of "make" will make it appear that there are no build failures, after all.
That's because the failed build products remain, with up-to-date timestamps, thus tricking Make (and you!) into believing that there's nothing else to build.
Fix this by telling Make to delete targets that didn't completely succeed.
Signed-off-by: John Hubbard jhubbard@nvidia.com --- tools/testing/selftests/vm/Makefile | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile index a9026706d597..9f2625bebf07 100644 --- a/tools/testing/selftests/vm/Makefile +++ b/tools/testing/selftests/vm/Makefile @@ -3,6 +3,11 @@ uname_M := $(shell uname -m 2>/dev/null || echo not) MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/')
+# Without this, failed build products remain, with up-to-date timestamps, +# thus tricking Make (and you!) into believing that All Is Well, in subsequent +# make invocations: +.DELETE_ON_ERROR: + CFLAGS = -Wall -I ../../../../usr/include $(EXTRA_CFLAGS) LDLIBS = -lrt TEST_GEN_FILES = compaction_test
Avoid accidental wrong builds, due to built-in rules working just a little bit too well--but not quite as well as required for our situation here.
In other words, "make userfaultfd" (for example) is supposed to fail to build at all, because this Makefile only supports either "make" (all), or "make /full/path". However, the built-in rules, if not suppressed, will pick up CFLAGS and the initial LDLIBS (but not the target-specific LDLIBS, because those are only set for the full path target!). This causes it to get pretty far into building things despite using incorrect values such as an *occasionally* incomplete LDLIBS value.
Signed-off-by: John Hubbard jhubbard@nvidia.com --- tools/testing/selftests/vm/Makefile | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile index 9f2625bebf07..30873b19d04b 100644 --- a/tools/testing/selftests/vm/Makefile +++ b/tools/testing/selftests/vm/Makefile @@ -8,6 +8,18 @@ MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/') # make invocations: .DELETE_ON_ERROR:
+# Avoid accidental wrong builds, due to built-in rules working just a little +# bit too well--but not quite as well as required for our situation here. +# +# In other words, "make userfaultfd" is supposed to fail to build at all, +# because this Makefile only supports either "make" (all), or "make /full/path". +# However, the built-in rules, if not suppressed, will pick up CFLAGS and the +# initial LDLIBS (but not the target-specific LDLIBS, because those are only +# set for the full path target!). This causes it to get pretty far into building +# things despite using incorrect values such as an *occasionally* incomplete +# LDLIBS. +MAKEFLAGS += --no-builtin-rules + CFLAGS = -Wall -I ../../../../usr/include $(EXTRA_CFLAGS) LDLIBS = -lrt TEST_GEN_FILES = compaction_test
On Mon, Sep 14, 2020 at 06:29:01PM -0700, John Hubbard wrote:
Avoid accidental wrong builds, due to built-in rules working just a little bit too well--but not quite as well as required for our situation here.
In other words, "make userfaultfd" (for example) is supposed to fail to build at all, because this Makefile only supports either "make" (all), or "make /full/path". However, the built-in rules, if not suppressed, will pick up CFLAGS and the initial LDLIBS (but not the target-specific LDLIBS, because those are only set for the full path target!). This causes it to get pretty far into building things despite using incorrect values such as an *occasionally* incomplete LDLIBS value.
Signed-off-by: John Hubbard jhubbard@nvidia.com
tools/testing/selftests/vm/Makefile | 12 ++++++++++++ 1 file changed, 12 insertions(+)
I hit this too when fiddling with the hmm tests! Would be happy to see better errors
Jason
linux-kselftest-mirror@lists.linaro.org
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Jason Gunthorpe -
John Hubbard