From: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
To: Thomas Gummerer <t.gummerer@gmail.com>
Cc: git <git@vger.kernel.org>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Christian Couder" <christian.couder@gmail.com>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Kernel USP" <kernel-usp@googlegroups.com>,
"Benoit Pierre" <benoit.pierre@gmail.com>,
"Junio C Hamano" <gitster@pobox.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>
Subject: Re: [GSoC][PATCH v4 2/7] clone: better handle symlinked files at .git/objects/
Date: Mon, 1 Apr 2019 00:56:52 -0300 [thread overview]
Message-ID: <CAHd-oW7jJWyww1i6rLG60M91NJa4AV2nbyOaXA6KE=StmmN6_A@mail.gmail.com> (raw)
In-Reply-To: <20190330192738.GQ32487@hank.intra.tgummerer.com>
On Sat, Mar 30, 2019 at 4:27 PM Thomas Gummerer <t.gummerer@gmail.com> wrote:
>
> On 03/30, Matheus Tavares Bernardino wrote:
> > On Fri, Mar 29, 2019 at 5:05 PM Thomas Gummerer <t.gummerer@gmail.com> wrote:
> > >
> > > On 03/29, Matheus Tavares Bernardino wrote:
> > > > Ok, what if instead of using linkat() we use 'realpath(const char
> > > > *path, char *resolved_path)', which will resolve any symlinks at
> > > > 'path' and store the canonical path at 'resolved_path'? Then, we can
> > > > still keep using link() but now, with the certainty that all platforms
> > > > will have a consistent behaviour? (also, realpath() is POSIX.1-2001)
> > > > Would that be a better idea?
> > >
> > > Yeah, I think that is a good idea. Note that 'realpath()' itself is
> > > not used anywhere in our codebase either, but there is
> > > 'strbuf_realpath()', that from reading the function documentation does
> > > exactly what 'realpath()' would do. So using 'strbuf_realpath()'
> > > would probably be the right thing to do here.
> >
> > Thanks. While I was looking for realpath() at git codebase (before I
> > saw your email), I got a little confused: Besides strbuf_realpath() I
> > also found real_path(), real_path_if_valid() and real_pathdup(). All
> > these last three use strbuf_realpath() but they also initialize the
> > struct strbuf internally and just return a 'char *', which is much
> > convenient in some cases.
>
> Right, feel free to use whichever is most convenient for you, and
> whichever works in the context.
>
> > What seems weird to me is that, whilst
> > real_pathdup() releases the internally initialized struct strubuf
> > (leaving just the returned string to be free'd by the user), the other
> > two don't. So, if struct strbuf change in the future to have more
> > dynamic allocated resources, these functions will also have to be
> > modified. Also, since real_pathdup() can already do what the other two
> > do, do you know if there is a reason to keep all of them?
>
> Right, '*dup()' functions usually leave the return value to be free'd
> by the caller. And while 'real_pathdup()' could do what the others do
> already it also takes more effort to use it. Users don't need to free
> the return value from 'real_path()' to avoid a memory leak. This
> alone justifies its existence I think.
>
> > One last question: I found some places which don't free the string
> > returned by, for example, real_path() (e.g., find_worktree() at
> > worktree.c). Would it be a valid/good patch (or patches) to add free()
> > calls in this places? (I'm currently trying to get more people here at
> > USP to contribute to git, and maybe this could be a nice first
> > contribution for them...)
>
> Trying to plug memory leaks in the codebase is definitely something
> that I think is worthy of doing. Sometimes it's not worth actually
> free'ing the memory, for example just before the program exits, in
> which case we can use the UNLEAK annotation. It was introduced in
> 0e5bba53af ("add UNLEAK annotation for reducing leak false positives",
> 2017-09-08) if you want more background.
>
> That said, the memory from 'real_path()' should actually not be
> free'd. The strbuf there has a static lifetime, so it is valid until
> git exits. If we were to free the return value of the function we'd
> actually free an internal buffer of the strbuf, that is still valid.
> So if someone were to use 'real_path()' after that, the memory that
> strbuf still thinks it owns would actually have been free'd, which
> would result in undefined behaviour, and probably would make git
> segfault.
>
Thanks for the great explanation, Thomas. I hadn't noticed that the
strbuf variable inside real_path() is declared as static. I also took
some time, now, to better understand how strbuf functions deal with
the buf attribute (especially how it's realloc'ed) and now I think I
understand it better. Thanks again for the help!
> --
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next prev parent reply other threads:[~2019-04-01 3:57 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-26 5:17 [WIP RFC PATCH v2 0/5] clone: dir iterator refactoring with tests Matheus Tavares
2019-02-26 5:18 ` [WIP RFC PATCH v2 1/5] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-02-26 12:01 ` Duy Nguyen
2019-02-27 13:59 ` Matheus Tavares Bernardino
2019-02-26 5:18 ` [WIP RFC PATCH v2 2/5] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-02-26 5:18 ` [WIP RFC PATCH v2 3/5] clone: copy hidden paths at local clone Matheus Tavares
2019-02-26 12:13 ` Duy Nguyen
2019-02-26 5:18 ` [WIP RFC PATCH v2 4/5] clone: extract function from copy_or_link_directory Matheus Tavares
2019-02-26 12:18 ` Duy Nguyen
2019-02-27 17:30 ` Matheus Tavares Bernardino
2019-02-27 22:45 ` Thomas Gummerer
2019-02-27 22:50 ` Matheus Tavares Bernardino
2019-02-26 5:18 ` [WIP RFC PATCH v2 5/5] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-02-26 11:35 ` Ævar Arnfjörð Bjarmason
2019-02-26 12:32 ` Duy Nguyen
2019-02-26 12:50 ` Ævar Arnfjörð Bjarmason
2019-02-27 17:40 ` Matheus Tavares Bernardino
2019-02-28 7:13 ` Duy Nguyen
2019-02-28 7:53 ` Ævar Arnfjörð Bjarmason
2019-02-26 11:36 ` [WIP RFC PATCH v2 0/5] clone: dir iterator refactoring with tests Ævar Arnfjörð Bjarmason
2019-02-26 12:20 ` Duy Nguyen
2019-02-26 12:28 ` [RFC PATCH v3 " Ævar Arnfjörð Bjarmason
2019-02-26 20:56 ` Matheus Tavares Bernardino
2019-03-22 23:22 ` [GSoC][PATCH v4 0/7] clone: dir-iterator " Matheus Tavares
2019-03-22 23:22 ` [GSoC][PATCH v4 1/7] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-03-24 18:09 ` Matheus Tavares Bernardino
2019-03-24 20:56 ` SZEDER Gábor
2019-03-26 19:43 ` Matheus Tavares Bernardino
2019-03-28 21:49 ` Thomas Gummerer
2019-03-29 14:06 ` Matheus Tavares Bernardino
2019-03-29 19:31 ` Thomas Gummerer
2019-03-29 19:42 ` SZEDER Gábor
2019-03-30 2:49 ` Matheus Tavares Bernardino
2019-03-22 23:22 ` [GSoC][PATCH v4 2/7] clone: better handle symlinked files at .git/objects/ Matheus Tavares
2019-03-28 22:10 ` Thomas Gummerer
2019-03-29 8:38 ` Ævar Arnfjörð Bjarmason
2019-03-29 20:15 ` Thomas Gummerer
2019-03-29 14:27 ` Matheus Tavares Bernardino
2019-03-29 20:05 ` Thomas Gummerer
2019-03-30 5:32 ` Matheus Tavares Bernardino
2019-03-30 19:27 ` Thomas Gummerer
2019-04-01 3:56 ` Matheus Tavares Bernardino [this message]
2019-03-29 15:40 ` Johannes Schindelin
2019-03-22 23:22 ` [GSoC][PATCH v4 3/7] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-03-28 22:19 ` Thomas Gummerer
2019-03-29 13:16 ` Matheus Tavares Bernardino
2019-03-22 23:22 ` [GSoC][PATCH v4 4/7] clone: copy hidden paths at local clone Matheus Tavares
2019-03-22 23:22 ` [GSoC][PATCH v4 5/7] clone: extract function from copy_or_link_directory Matheus Tavares
2019-03-22 23:22 ` [GSoC][PATCH v4 6/7] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-03-22 23:22 ` [GSoC][PATCH v4 7/7] clone: Replace strcmp by fspathcmp Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 0/7] clone: dir-iterator refactoring with tests Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 1/7] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 2/7] clone: better handle symlinked files at .git/objects/ Matheus Tavares
2019-03-31 17:40 ` Thomas Gummerer
2019-04-01 3:59 ` Matheus Tavares Bernardino
2019-03-30 22:49 ` [GSoC][PATCH v5 3/7] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-03-31 18:12 ` Thomas Gummerer
2019-04-10 20:24 ` Matheus Tavares Bernardino
2019-04-11 21:09 ` Thomas Gummerer
2019-04-23 17:07 ` Matheus Tavares Bernardino
2019-04-24 18:36 ` Thomas Gummerer
2019-04-26 4:13 ` Matheus Tavares Bernardino
2019-03-30 22:49 ` [GSoC][PATCH v5 4/7] clone: copy hidden paths at local clone Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 5/7] clone: extract function from copy_or_link_directory Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 6/7] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-03-30 22:49 ` [GSoC][PATCH v5 7/7] clone: replace strcmp by fspathcmp Matheus Tavares
2019-03-31 18:16 ` [GSoC][PATCH v5 0/7] clone: dir-iterator refactoring with tests Thomas Gummerer
2019-04-01 13:56 ` Matheus Tavares Bernardino
2019-05-02 14:48 ` [GSoC][PATCH v6 00/10] " Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 01/10] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 02/10] clone: better handle symlinked files at .git/objects/ Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 03/10] dir-iterator: add tests for dir-iterator API Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 04/10] dir-iterator: use warning_errno when possible Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 05/10] dir-iterator: refactor state machine model Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 06/10] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 07/10] clone: copy hidden paths at local clone Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 08/10] clone: extract function from copy_or_link_directory Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 09/10] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-05-02 14:48 ` [GSoC][PATCH v6 10/10] clone: replace strcmp by fspathcmp Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 00/10] clone: dir-iterator refactoring with tests Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 01/10] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 02/10] clone: better handle symlinked files at .git/objects/ Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 03/10] dir-iterator: add tests for dir-iterator API Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 04/10] dir-iterator: use warning_errno when possible Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 05/10] dir-iterator: refactor state machine model Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 06/10] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-06-25 18:00 ` Junio C Hamano
2019-06-25 18:11 ` Matheus Tavares Bernardino
2019-06-26 13:34 ` Johannes Schindelin
2019-06-26 18:04 ` Junio C Hamano
2019-06-27 9:20 ` Duy Nguyen
2019-06-27 17:23 ` Matheus Tavares Bernardino
2019-06-27 18:48 ` Johannes Schindelin
2019-06-27 19:33 ` Matheus Tavares Bernardino
2019-06-28 12:51 ` Johannes Schindelin
2019-06-28 14:16 ` Matheus Tavares Bernardino
2019-07-01 12:15 ` Johannes Schindelin
2019-07-03 8:57 ` SZEDER Gábor
2019-07-08 22:21 ` Matheus Tavares Bernardino
2019-06-18 23:27 ` [GSoC][PATCH v7 07/10] clone: copy hidden paths at local clone Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 08/10] clone: extract function from copy_or_link_directory Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 09/10] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-06-18 23:27 ` [GSoC][PATCH v7 10/10] clone: replace strcmp by fspathcmp Matheus Tavares
2019-06-19 4:36 ` [GSoC][PATCH v7 00/10] clone: dir-iterator refactoring with tests Matheus Tavares Bernardino
2019-06-20 20:18 ` Junio C Hamano
2019-06-21 13:41 ` Matheus Tavares Bernardino
2019-07-10 23:58 ` [GSoC][PATCH v8 " Matheus Tavares
2019-07-10 23:58 ` [GSoC][PATCH v8 01/10] clone: test for our behavior on odd objects/* content Matheus Tavares
2019-07-10 23:58 ` [GSoC][PATCH v8 02/10] clone: better handle symlinked files at .git/objects/ Matheus Tavares
2019-07-10 23:58 ` [GSoC][PATCH v8 03/10] dir-iterator: add tests for dir-iterator API Matheus Tavares
2019-07-10 23:58 ` [GSoC][PATCH v8 04/10] dir-iterator: use warning_errno when possible Matheus Tavares
2019-07-10 23:58 ` [GSoC][PATCH v8 05/10] dir-iterator: refactor state machine model Matheus Tavares
2019-07-10 23:59 ` [GSoC][PATCH v8 06/10] dir-iterator: add flags parameter to dir_iterator_begin Matheus Tavares
2019-07-10 23:59 ` [GSoC][PATCH v8 07/10] clone: copy hidden paths at local clone Matheus Tavares
2019-07-10 23:59 ` [GSoC][PATCH v8 08/10] clone: extract function from copy_or_link_directory Matheus Tavares
2019-07-10 23:59 ` [GSoC][PATCH v8 09/10] clone: use dir-iterator to avoid explicit dir traversal Matheus Tavares
2019-07-10 23:59 ` [GSoC][PATCH v8 10/10] clone: replace strcmp by fspathcmp Matheus Tavares
2019-07-11 11:56 ` [GSoC][PATCH v8 00/10] clone: dir-iterator refactoring with tests Johannes Schindelin
2019-07-11 15:24 ` Matheus Tavares Bernardino
2019-02-26 12:28 ` [RFC PATCH v3 1/5] clone: test for our behavior on odd objects/* content Ævar Arnfjörð Bjarmason
2019-02-28 21:19 ` Matheus Tavares Bernardino
2019-03-01 13:49 ` Ævar Arnfjörð Bjarmason
2019-03-13 3:17 ` Matheus Tavares
2019-02-26 12:28 ` [RFC PATCH v3 2/5] dir-iterator: add flags parameter to dir_iterator_begin Ævar Arnfjörð Bjarmason
2019-02-26 12:28 ` [RFC PATCH v3 3/5] clone: copy hidden paths at local clone Ævar Arnfjörð Bjarmason
2019-02-26 12:28 ` [RFC PATCH v3 4/5] clone: extract function from copy_or_link_directory Ævar Arnfjörð Bjarmason
2019-02-26 12:28 ` [RFC PATCH v3 5/5] clone: use dir-iterator to avoid explicit dir traversal Ævar Arnfjörð Bjarmason
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