From: Johannes Schindelin <Johannes.Schindelin@gmx.de> To: Jeff King <firstname.lastname@example.org> Cc: "Johannes Schindelin via GitGitGadget" <email@example.com>, firstname.lastname@example.org, 마누엘 <email@example.com> Subject: Re: [PATCH] clean: explicitly `fflush` stdout Date: Fri, 10 Apr 2020 16:03:26 +0200 (CEST) [thread overview] Message-ID: <nycvar.QRO.firstname.lastname@example.org> (raw) In-Reply-To: <20200408201454.GB2270445@coredump.intra.peff.net> Hi Peff, On Wed, 8 Apr 2020, Jeff King wrote: > On Wed, Apr 08, 2020 at 07:33:00PM +0000, Johannes Schindelin via GitGitGadget wrote: > > > From: =?UTF-8?q?=EB=A7=88=EB=88=84=EC=97=98?= <email@example.com> > > > > For performance reasons `stdout` is buffered by default. That leads to > > problems if after printing to `stdout` a read on `stdin` is performed. > > This first paragraph left me scratching my head. It's only a problem for > interactive uses, right? Would: > > This can lead to problems for interactive commands which write a > prompt to `stdout` and then read user input on `stdin`. If the prompt > is left in the buffer, the user will not realize the program is > waiting for their input. > > make sense? Thank you, yes, that makes sense. Based on another suggestion of yours, I did refactor the code a bit more and already sent out the result as v2. Thank you, Dscho > > > For that reason interactive commands like `git clean -i` do not function > > properly anymore if the `stdout` is not flushed by `fflush(stdout)` before > > trying to read from `stdin`. > > I'm not sure I understand this "anymore". Did the buffering change at > some point, introducing a regression? > > > So let's precede all reads on `stdin` in `git clean -i` by flushing > > `stdout`. > > This (and the patch) make sense to me. It might be worth factoring out a > "read input from user" function and putting the flush there, but with > only three affected call sites, I'm OK with it either way. > > > This is yet another patch that was funneled through a Git for Windows > > PR. It has served us well for almost five years now, and it is beyond > > time that it find its final home in core Git. > > Agreed. I guess it didn't affect people on other platforms much because > stdout to a terminal is generally line-buffered on POSIX systems. But > it's better not to rely on that, plus it could create confusion if > somebody tried to manipulate the interactive operation through a pipe > (e.g., driving it from a GUI or something). > > -Peff >
next prev parent reply other threads:[~2020-04-10 14:03 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-08 19:33 Johannes Schindelin via GitGitGadget 2020-04-08 20:14 ` Jeff King 2020-04-08 21:51 ` Junio C Hamano 2020-04-08 22:38 ` Jeff King 2020-04-10 14:03 ` Johannes Schindelin [this message] 2020-04-10 11:27 ` [PATCH v2 0/2] Explicitly fflush stdout in git clean Johannes Schindelin via GitGitGadget 2020-04-10 11:27 ` [PATCH v2 1/2] Refactor code asking the user for input interactively Johannes Schindelin via GitGitGadget 2020-04-10 12:27 ` Derrick Stolee 2020-04-10 14:01 ` Johannes Schindelin 2020-04-10 15:07 ` Jeff King 2020-04-10 17:44 ` Junio C Hamano 2020-04-10 11:27 ` [PATCH v2 2/2] Explicitly `fflush` stdout before expecting interactive input 마누엘 via GitGitGadget 2020-04-10 12:28 ` Derrick Stolee 2020-04-10 18:16 ` [PATCH v3 0/2] Explicitly fflush stdout in git clean Johannes Schindelin via GitGitGadget 2020-04-10 18:16 ` [PATCH v3 1/2] Refactor code asking the user for input interactively Johannes Schindelin via GitGitGadget 2020-04-10 18:16 ` [PATCH v3 2/2] Explicitly `fflush` stdout before expecting interactive input 마누엘 via GitGitGadget
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