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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Junio C Hamano <gitster@pobox.com>
Cc: Johannes Sixt <j6t@kdbg.org>,
	Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org
Subject: Re: [PATCH v2 0/2] Brown-bag fix on top of js/mingw-inherit-only-std-handles
Date: Mon, 2 Dec 2019 10:05:08 +0100 (CET)
Message-ID: <nycvar.QRO.7.76.6.1912021001510.31080@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <xmqqk17fz2e7.fsf@gitster-ct.c.googlers.com>

Hi Junio,

On Sun, 1 Dec 2019, Junio C Hamano wrote:

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>
> > But the intention is not to help correct callers! The purpose of mapping
> > `ERROR_SUCCESS` to 0 will help _only_ callers that try to report an error
> > when none happened. On Windows, which is the only platform where the
> > discussed function is compiled and used, `strerror(0)` has the
> > well-established behavior of returning "No error".
>
> But is the caller that ends up saying "No error" you mention below
> by calling strerror() exists *only* on Windows port somewhere in
> compat/ directory?  If the call to strerror() is made from a
> codepath that is common to all platforms, then that caller *is*
> wrong to do so after seeing *no* errors.

Yes, that would be a difference between platforms, but _at least_ the
Windows side would help diagnose the bug better. I'd prefer such a half
solution to having no solution at all.

> So, no, sorry, but I do not understand the above line of reasoning.
>
> > Now imagine that a user encounters a bug where a code path does indeed
> > incorrectly report an error where no error occurred (or where Git is
> > looking for the error too late or something like that). You probably agree
> > with me that we should really avoid reporting "Function not implemented"
> > in such a case and rather say "No error", which will help figure out the
> > bug much quicker.
>
> Not really.  A BUG() that catches a call to this function that
> should not be called when there is no error would help identify the
> problematic caller a lot faster by being louder---those users who
> get hit will raise their hands more readily than those who see "No
> error" and wonders "why does Git give that error message when there
> is no error?".  IOW, "No error" sounds like sweeping the issue under
> the rug.

This is a very good point. It _is_ a bug to hit that code path when
`GetLastError()` returned `ERROR_SUCCESS`, and having such a `BUG()` call
would have prevented the bug that I fix in 1/2 from slipping through.

Therefore, I changed 2/2 to raise a BUG() and am currently waiting for the
PR build to finish before sending another iteration of this seris.

Ciao,
Dscho

> The argument could be "I do not want to be pressured to hunt for the
> problematic caller, and taking the approach to be less loud than the
> BUG() approach would allow the end users keep operating as if
> nothing bad happened, so that I can hunt for the caller iff/when I
> feel like it, and with no urgent need I can just ignore the hunt
> altogether.  Not hitting with BUG() is a service to the end users
> who shouldn't be made a guinea pig---that is why we want to sweep
> the problematic caller under the rug.  It may delay the discovery
> and fixing of problematic callers, which is a downside, though."
>
> I would understand such an argument, even if I might not think that
> such an argument makes the right tradeoff between not hitting the
> users with BUG() and not being effective in finding the problematic
> caller.
>
> Thanks.
>
>

  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-29 21:44 [PATCH 0/1] " Johannes Schindelin via GitGitGadget
2019-11-29 21:44 ` [PATCH 1/1] mingw: do set `errno` correctly when trying to restrict handle inheritance Johannes Schindelin via GitGitGadget
2019-11-29 23:02   ` Johannes Sixt
2019-11-30 22:06     ` Johannes Schindelin
2019-11-30 22:16       ` Johannes Sixt
2019-11-30 10:36 ` [PATCH v2 0/2] Brown-bag fix on top of js/mingw-inherit-only-std-handles Johannes Schindelin via GitGitGadget
2019-11-30 10:36   ` [PATCH v2 1/2] mingw: do set `errno` correctly when trying to restrict handle inheritance Johannes Schindelin via GitGitGadget
2019-11-30 10:36   ` [PATCH v2 2/2] mingw: translate ERROR_SUCCESS to errno = 0 Johannes Schindelin via GitGitGadget
2019-11-30 18:04   ` [PATCH v2 0/2] Brown-bag fix on top of js/mingw-inherit-only-std-handles Junio C Hamano
2019-11-30 19:13     ` Johannes Sixt
2019-11-30 20:11       ` Andreas Schwab
2019-11-30 20:23         ` Junio C Hamano
2019-11-30 20:43           ` Andreas Schwab
2019-11-30 21:22             ` Johannes Schindelin
2019-11-30 20:21       ` Junio C Hamano
2019-12-01  6:26         ` Junio C Hamano
2019-12-01  9:53           ` Johannes Schindelin
2019-12-02  6:07             ` Junio C Hamano
2019-12-02  9:05               ` Johannes Schindelin [this message]
2019-11-30 19:20   ` Johannes Sixt
2019-11-30 22:09     ` Junio C Hamano
2019-12-02 11:33   ` [PATCH v3 " Johannes Schindelin via GitGitGadget
2019-12-02 11:33     ` [PATCH v3 1/2] mingw: do set `errno` correctly when trying to restrict handle inheritance Johannes Schindelin via GitGitGadget
2019-12-02 11:33     ` [PATCH v3 2/2] mingw: translate ERROR_SUCCESS to errno = 0 Johannes Schindelin via GitGitGadget
2019-12-02 17:35     ` [PATCH v3 0/2] Brown-bag fix on top of js/mingw-inherit-only-std-handles Johannes Sixt
2019-12-02 19:04       ` Junio C Hamano
2019-12-03 12:04       ` Johannes Schindelin

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