From: Taylor Blau <me@ttaylorr.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Taylor Blau <me@ttaylorr.com>,
git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Han-Wen Nienhuys <hanwen@google.com>
Subject: Re: [PATCH 2/3] reftable: remove unreachable "return" statements
Date: Wed, 12 Jan 2022 14:19:40 -0500 [thread overview]
Message-ID: <Yd8pzOh1HLvDWSPg@nand.local> (raw)
In-Reply-To: <220112.865yqpxge2.gmgdl@evledraar.gmail.com>
On Wed, Jan 12, 2022 at 01:47:40PM +0100, Ævar Arnfjörð Bjarmason wrote:
> >> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> >> ---
> >> reftable/refname.c | 1 -
> >> reftable/writer.c | 1 -
> >> 2 files changed, 2 deletions(-)
> >>
> >> diff --git a/reftable/refname.c b/reftable/refname.c
> >> index 95734969324..136001bc2c7 100644
> >> --- a/reftable/refname.c
> >> +++ b/reftable/refname.c
> >> @@ -132,7 +132,6 @@ static int validate_refname(const char *name)
> >> return REFTABLE_REFNAME_ERROR;
> >> name = next + 1;
> >> }
> >> - return 0;
> >> }
> >
> > In this case the loop inside of validate_refname() should always
> > terminate the function within the loop body. But removing this return
> > statement here relies on the compiler to determine that fact.
> >
> > I could well imagine on the other end of the spectrum there exists a
> > compiler which _doesn't_ make this inference pass, and would complain
> > about the opposite thing as you're reporting from SunCC (i.e., that this
> > function which returns something other than void does not have a return
> > statement outside of the loop).
> >
> > So in that sense, I disagree with the guidance of SunCC's warning. In
> > other words: by quelching this warning under one compiler, are we
> > introducing a new warning under a different/less advanced compiler?
>
> I'd think that any compiler who'd warn about this sort of thing at all
> would be able to spot constructs like this one, which are basically:
>
> while (1) {
> ...
> if (x)
> return;
> ...
> }
> return; /* unreachable */
>
> Where the elided code contains no "break", "goto" or other mechanism for
> exiting the for-loop.
>
> I.e. GCC and Clang don't bother to note the unreachable code, but I
> don't think the reverse will be true, that a compiler will say that a
> "return" is missing there. Having a function be just a loop body that
> returns an some point is a common pattern.
Right, but I'm more concerned about a less advanced compiler that would
complain about the absence of a `return` statement as the last
instruction in a non-void function.
This is probably all academic, anyway, since less advanced compilers
probably have other issues compiling Git as it stands today, but
fundamentally I think that SunCC's warnings here are at the very least
inconsiderate of less advanced compilers.
To me, the safest thing to do would be to leave the code as-is and drop
this patch.
Thanks,
Taylor
next prev parent reply other threads:[~2022-01-12 19:25 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 16:40 [PATCH 0/3] Fix SunCC compiler complaints new in v2.35.0-rc0 Ævar Arnfjörð Bjarmason
2022-01-11 16:40 ` [PATCH 1/3] test-tool genzeros: initialize "zeros" to avoid SunCC warning Ævar Arnfjörð Bjarmason
2022-01-11 19:06 ` Taylor Blau
2022-01-12 14:21 ` Johannes Schindelin
2022-01-12 19:10 ` Taylor Blau
2022-01-13 10:08 ` Ævar Arnfjörð Bjarmason
2022-01-13 15:31 ` Johannes Schindelin
2022-01-13 17:38 ` Junio C Hamano
2022-01-11 16:40 ` [PATCH 2/3] reftable: remove unreachable "return" statements Ævar Arnfjörð Bjarmason
2022-01-11 19:16 ` Taylor Blau
2022-01-12 12:47 ` Ævar Arnfjörð Bjarmason
2022-01-12 19:19 ` Taylor Blau [this message]
2022-01-13 10:29 ` Ævar Arnfjörð Bjarmason
2022-01-13 15:39 ` Johannes Schindelin
2022-01-13 20:17 ` Johannes Sixt
2022-01-13 21:37 ` Junio C Hamano
2022-01-11 16:40 ` [PATCH 3/3] reftable tests: avoid "int" overflow, use "uint64_t" Ævar Arnfjörð Bjarmason
2022-01-11 19:28 ` Taylor Blau
2022-01-11 19:31 ` Han-Wen Nienhuys
2022-01-11 19:41 ` Taylor Blau
2022-01-11 20:08 ` Johannes Sixt
2022-01-11 20:18 ` Taylor Blau
2022-01-11 20:21 ` Johannes Sixt
2022-01-11 20:24 ` Taylor Blau
2022-01-12 14:18 ` Johannes Schindelin
2022-01-12 19:02 ` Junio C Hamano
2022-01-12 19:07 ` Taylor Blau
2022-01-13 10:04 ` Ævar Arnfjörð Bjarmason
2022-01-13 21:38 ` Junio C Hamano
2022-01-11 17:06 ` [PATCH 0/3] Fix SunCC compiler complaints new in v2.35.0-rc0 Han-Wen Nienhuys
2022-01-11 18:36 ` René Scharfe
2022-01-12 1:22 ` Emily Shaffer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Yd8pzOh1HLvDWSPg@nand.local \
--to=me@ttaylorr.com \
--cc=Johannes.Schindelin@gmx.de \
--cc=avarab@gmail.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=hanwen@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).