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Re: [PATCH v2 0/2] Brown-bag fix on top of js/mingw-inherit-only-std-handles

From
Johannes Schindelin <johannes.schindelin@gmx.de>
Date
Dec 2, 2019, 09:05 UTC
Message-ID
<nycvar.QRO.7.76.6.1912021001510.31080@tvgsbejvaqbjf.bet>
In-Reply-To
<xmqqk17fz2e7.fsf@gitster-ct.c.googlers.com>
Hi Junio,
On Sun, 1 Dec 2019, Junio C Hamano wrote:
Show 13 quoted lines
> 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.

Show 16 quoted lines
> 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

Show 18 quoted lines
> 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.
>
>
Previous: Junio C HamanoNext: Johannes Sixt
Message 19 of 27 in “Brown-bag fix on top of js/mingw-inherit-only-std-handles”
  1. 0/1 Brown-bag fix on top of js/mingw-inherit-only-std-handlesJohannes Schindelin via GitGitGadget, Nov 29, 2019
  2. 1/1 mingw: do set `errno` correctly when trying to restrict handle inheritanceJohannes Schindelin via GitGitGadget, Nov 29, 2019
  3. Johannes SixtNov 29, 2019
  4. Johannes SchindelinNov 30, 2019
  5. Johannes SixtNov 30, 2019
  6. 0/2 Brown-bag fix on top of js/mingw-inherit-only-std-handlesJohannes Schindelin via GitGitGadget, Nov 30, 2019
  7. 1/2 mingw: do set `errno` correctly when trying to restrict handle inheritanceJohannes Schindelin via GitGitGadget, Nov 30, 2019
  8. 2/2 mingw: translate ERROR_SUCCESS to errno = 0Johannes Schindelin via GitGitGadget, Nov 30, 2019
  9. Junio C HamanoNov 30, 2019
  10. Johannes SixtNov 30, 2019
  11. Andreas SchwabNov 30, 2019
  12. Junio C HamanoNov 30, 2019
  13. Andreas SchwabNov 30, 2019
  14. Johannes SchindelinNov 30, 2019
  15. Junio C HamanoNov 30, 2019
  16. Junio C HamanoDec 1, 2019
  17. Johannes SchindelinDec 1, 2019
  18. Junio C HamanoDec 2, 2019
  19. Johannes SchindelinDec 2, 2019
  20. Johannes SixtNov 30, 2019
  21. Junio C HamanoNov 30, 2019
  22. 0/2 Brown-bag fix on top of js/mingw-inherit-only-std-handlesJohannes Schindelin via GitGitGadget, Dec 2, 2019
  23. 2/2 mingw: translate ERROR_SUCCESS to errno = 0Johannes Schindelin via GitGitGadget, Dec 2, 2019
  24. 1/2 mingw: do set `errno` correctly when trying to restrict handle inheritanceJohannes Schindelin via GitGitGadget, Dec 2, 2019
  25. Johannes SixtDec 2, 2019
  26. Junio C HamanoDec 2, 2019
  27. Johannes SchindelinDec 3, 2019

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