From: Josh Steadmon <steadmon@google.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Bagas Sanjaya <bagasdotme@gmail.com>,
Abhradeep Chakraborty <chakrabortyabhradeep79@gmail.com>,
Glen Choo <chooglen@google.com>,
Andrei Rybak <rybak.a.v@gmail.com>,
Emily Shaffer <emilyshaffer@google.com>
Subject: Re: [PATCH v3 1/6] common-main.o: move non-trace2 exit() behavior out of trace2.c
Date: Tue, 7 Jun 2022 15:05:57 -0700 [thread overview]
Message-ID: <Yp/LxRguys1FRJHH@google.com> (raw)
In-Reply-To: <220607.8635ggupws.gmgdl@evledraar.gmail.com>
On 2022.06.07 23:12, Ævar Arnfjörð Bjarmason wrote:
>
> On Tue, Jun 07 2022, Josh Steadmon wrote:
>
> > On 2022.06.02 14:25, Ævar Arnfjörð Bjarmason wrote:
> >> Change the exit() wrapper added in ee4512ed481 (trace2: create new
> >> combined trace facility, 2019-02-22) so that we'll split up the trace2
> >> logging concerns from wanting to wrap the "exit()" function itself for
> >> other purposes.
> >>
> >> This makes more sense structurally, as we won't seem to conflate
> >> non-trace2 behavior with the trace2 code. I'd previously added an
> >> explanation for this in 368b5843158 (common-main.c: call exit(), don't
> >> return, 2021-12-07), that comment is being adjusted here.
> >>
> >> Now the only thing we'll do if we're not using trace2 is to truncate
> >> the "code" argument to the lowest 8 bits.
> >>
> >> We only need to do that truncation on non-POSIX systems, but in
> >> ee4512ed481 that "if defined(__MINGW32__)" code added in
> >> 47e3de0e796 (MinGW: truncate exit()'s argument to lowest 8 bits,
> >> 2009-07-05) was made to run everywhere. It might be good for clarify
> >> to narrow that down by an "ifdef" again, but I'm not certain that in
> >> the interim we haven't had some other non-POSIX systems rely the
> >> behavior. On a POSIX system taking the lowest 8 bits is implicit, see
> >> exit(3)[1] and wait(2)[2]. Let's leave a comment about that instead.
> >>
> >> 1. https://man7.org/linux/man-pages/man3/exit.3.html
> >> 2. https://man7.org/linux/man-pages/man2/wait.2.html
> >>
> >> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> >> ---
> >> common-main.c | 20 ++++++++++++++++----
> >> git-compat-util.h | 4 ++--
> >> trace2.c | 8 ++------
> >> trace2.h | 8 +-------
> >> 4 files changed, 21 insertions(+), 19 deletions(-)
> >
> > Just realized that this unexpectedly breaks the fuzzer builds:
> >
> > $ git checkout ab/bug-if-bug
> > $ make CC=clang CXX=clang++ \
> > CFLAGS="-fsanitize=fuzzer-no-link,address" \
> > LIB_FUZZING_ENGINE="-fsanitize=fuzzer" \
> > fuzz-all
> >
> > [...]
> > LINK fuzz-pack-headers
> > LINK fuzz-pack-idx
> > /usr/bin/ld: archive.o: in function `parse_archive_args':
> > archive.c:(.text.parse_archive_args[parse_archive_args]+0x2cb8): undefined reference to `common_exit'
> > [...]
>
> Hrm, that's a pain, sorry about that.
>
> > The issue is that we don't link the fuzzers against common-main.o
> > because the fuzzing engine provides its own main(). Would it be too much
> > of a pain to move this out to a new common-exit.c file?
>
> I could do that, I actually did that in a WIP copy, but figured it was
> too much boilerplate to pass the list.
>
> But why it is that we can't just link to common-main.o? Yeah the linker
> error, but we already depend on modern clang here, so can't we just use
> -Wl,--allow-multiple-definition?
>
> This works for me with my local clang & GNU ld:
>
> make CC=clang CXX=clang++ \
> CFLAGS="-fsanitize=fuzzer-no-link,address" \
> FUZZ_CXXFLAGS="-fsanitize=fuzzer-no-link,address -Wl,--allow-multiple-definition" \
> LIB_FUZZING_ENGINE="common-main.o -fsanitize=fuzzer" fuzz-all
>
> It seems to me that the $(FUZZ_PROGRAMS) rule is mostly trying to work
> around that by size, i.e. re-declaring most of $(OBJECTS).
>
> But maybe it's a no-go for some reason, maybe due to OSX ld?
Ah yeah, that would probably work. The main concern is that we want
these to run via OSS-Fuzz[1], but I believe I can send a change to our
build script there to add that flag. Thanks for the suggestion!
[1]: https://google.github.io/oss-fuzz/
next prev parent reply other threads:[~2022-06-08 2:48 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-21 17:14 [PATCH 0/5] usage API: add and use a bug() + BUG_if_bug() Ævar Arnfjörð Bjarmason
2022-05-21 17:14 ` [PATCH 1/5] usage.c: add a non-fatal bug() function to go with BUG() Ævar Arnfjörð Bjarmason
2022-05-25 20:55 ` Junio C Hamano
2022-05-26 4:17 ` Junio C Hamano
2022-05-26 7:59 ` Ævar Arnfjörð Bjarmason
2022-05-26 16:55 ` Junio C Hamano
2022-05-26 18:29 ` Ævar Arnfjörð Bjarmason
2022-05-26 18:55 ` Junio C Hamano
2022-05-31 16:52 ` Ævar Arnfjörð Bjarmason
2022-05-27 17:03 ` Josh Steadmon
2022-05-27 19:05 ` Junio C Hamano
2022-05-21 17:14 ` [PATCH 2/5] parse-options.c: use new bug() API for optbug() Ævar Arnfjörð Bjarmason
2022-05-27 17:03 ` Josh Steadmon
2022-05-21 17:14 ` [PATCH 3/5] parse-options.c: use optbug() instead of BUG() "opts" check Ævar Arnfjörð Bjarmason
2022-05-25 21:05 ` Junio C Hamano
2022-05-21 17:14 ` [PATCH 4/5] receive-pack: use bug() and BUG_if_bug() Ævar Arnfjörð Bjarmason
2022-05-25 21:15 ` Junio C Hamano
2022-05-27 17:04 ` Josh Steadmon
2022-05-27 22:53 ` Andrei Rybak
2022-05-21 17:14 ` [PATCH 5/5] cache-tree.c: " Ævar Arnfjörð Bjarmason
2022-05-27 21:29 ` Glen Choo
2022-05-27 17:02 ` [PATCH 0/5] usage API: add and use a bug() + BUG_if_bug() Josh Steadmon
2022-05-31 16:58 ` [PATCH v2 0/6] " Ævar Arnfjörð Bjarmason
2022-05-31 16:58 ` [PATCH v2 1/6] common-main.o: move non-trace2 exit() behavior out of trace2.c Ævar Arnfjörð Bjarmason
2022-06-01 18:37 ` Junio C Hamano
2022-05-31 16:58 ` [PATCH v2 2/6] usage.c: add a non-fatal bug() function to go with BUG() Ævar Arnfjörð Bjarmason
2022-05-31 18:18 ` Glen Choo
2022-06-01 18:50 ` Junio C Hamano
2022-05-31 16:58 ` [PATCH v2 3/6] parse-options.c: use new bug() API for optbug() Ævar Arnfjörð Bjarmason
2022-05-31 16:58 ` [PATCH v2 4/6] parse-options.c: use optbug() instead of BUG() "opts" check Ævar Arnfjörð Bjarmason
2022-05-31 17:38 ` Josh Steadmon
2022-06-01 18:55 ` Junio C Hamano
2022-05-31 16:58 ` [PATCH v2 5/6] receive-pack: use bug() and BUG_if_bug() Ævar Arnfjörð Bjarmason
2022-05-31 16:58 ` [PATCH v2 6/6] cache-tree.c: " Ævar Arnfjörð Bjarmason
2022-06-01 18:52 ` Junio C Hamano
2022-05-31 17:39 ` [PATCH v2 0/6] usage API: add and use a bug() + BUG_if_bug() Josh Steadmon
2022-06-02 12:25 ` [PATCH v3 " Ævar Arnfjörð Bjarmason
2022-06-02 12:25 ` [PATCH v3 1/6] common-main.o: move non-trace2 exit() behavior out of trace2.c Ævar Arnfjörð Bjarmason
2022-06-03 1:19 ` Junio C Hamano
2022-06-07 20:09 ` Josh Steadmon
2022-06-07 21:12 ` Ævar Arnfjörð Bjarmason
2022-06-07 22:05 ` Josh Steadmon [this message]
2022-06-02 12:25 ` [PATCH v3 2/6] usage.c: add a non-fatal bug() function to go with BUG() Ævar Arnfjörð Bjarmason
2022-06-02 12:25 ` [PATCH v3 3/6] parse-options.c: use new bug() API for optbug() Ævar Arnfjörð Bjarmason
2022-06-02 12:25 ` [PATCH v3 4/6] parse-options.c: use optbug() instead of BUG() "opts" check Ævar Arnfjörð Bjarmason
2022-06-02 12:25 ` [PATCH v3 5/6] receive-pack: use bug() and BUG_if_bug() Ævar Arnfjörð Bjarmason
2022-06-02 12:25 ` [PATCH v3 6/6] cache-tree.c: " Ævar Arnfjörð Bjarmason
2022-06-02 19:54 ` Junio C Hamano
2022-06-02 16:56 ` [PATCH v3 0/6] usage API: add and use a bug() + BUG_if_bug() Glen Choo
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