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Re: [PATCH v3 20/23] try_remove_empty_parents(): don't trash argument contents

From
Jeff King <peff@peff.net>
Date
Jan 2, 2017, 17:10 UTC
Message-ID
<20170102171043.ebfeaaylf4waq6co@sigill.intra.peff.net>
In-Reply-To
<9215973c-8db1-8f5a-2dc7-3a0137dd5c62@alum.mit.edu>
On Mon, Jan 02, 2017 at 05:27:59PM +0100, Michael Haggerty wrote:
Show 18 quoted lines
> > or something. But I doubt the single allocation is breaking the bank,
> > and it has the nice side effect that callers can pass in a const string
> > (I didn't check yet whether that enables further cleanups).
> 
> The last patch in the series passes ref_update::refname to this
> function, which is `const char *`. With your suggested change, either
> that member would have to be made non-const, or it would have to be cast
> to const at the `try_remove_empty_parents()` callsite.
> 
> Making the member non-const would be easy, though it loses a tiny bit of
> documentation and safety against misuse. Also, scribbling even
> temporarily over that member would mean that this code is not
> thread-safe (though it seems unlikely that we would ever bother making
> it multithreaded).
> 
> I think I prefer the current version because it loosens the coupling
> between this function and its callers. But I don't mind either way if
> somebody feels strongly about it.
OK, let's take what you have here, then.
> As an aside, I wonder whether we would be discussing this at all if we
> had stack-allocated strbufs that could be used without allocating heap
> memory in the usual case.

I'm not sure. We still pay the memcpy(), though I don't know how substantial that is compared to an allocation. For these small strings, probably not very.

-Peff
Previous: Michael HaggertyNext: Michael Haggerty
Message 28 of 55 in “Delete directories left empty after ref deletion”
  1. 00/23 Delete directories left empty after ref deletionMichael Haggerty, Dec 31, 2016
  2. 01/23 files_rename_ref(): tidy up whitespaceMichael Haggerty, Dec 31, 2016
  3. 02/23 t5505: use "for-each-ref" to test for the non-existence of referencesMichael Haggerty, Dec 31, 2016
  4. 03/23 safe_create_leading_directories_const(): preserve errnoMichael Haggerty, Dec 31, 2016
  5. 05/23 raceproof_create_file(): new functionMichael Haggerty, Dec 31, 2016
  6. Jeff KingDec 31, 2016
  7. Michael HaggertyDec 31, 2016
  8. Junio C HamanoJan 1, 2017
  9. 06/23 lock_ref_sha1_basic(): inline constantMichael Haggerty, Dec 31, 2016
  10. 07/23 lock_ref_sha1_basic(): use raceproof_create_file()Michael Haggerty, Dec 31, 2016
  11. 13/23 log_ref_setup(): pass the open file descriptor back to the callerMichael Haggerty, Dec 31, 2016
  12. Jeff KingDec 31, 2016
  13. Michael HaggertyDec 31, 2016
  14. Jeff KingDec 31, 2016
  15. Junio C HamanoJan 1, 2017
  16. 12/23 log_ref_setup(): improve robustness against racesMichael Haggerty, Dec 31, 2016
  17. 11/23 log_ref_setup(): separate code for create vs non-createMichael Haggerty, Dec 31, 2016
  18. Jeff KingDec 31, 2016
  19. Michael HaggertyDec 31, 2016
  20. Junio C HamanoJan 1, 2017
  21. Michael HaggertyJan 1, 2017
  22. 15/23 log_ref_setup(): manage the name of the reflog file internallyMichael Haggerty, Dec 31, 2016
  23. 16/23 log_ref_write_1(): inline functionMichael Haggerty, Dec 31, 2016
  24. 19/23 try_remove_empty_parents(): rename parameter "name" -> "refname"Michael Haggerty, Dec 31, 2016
  25. 20/23 try_remove_empty_parents(): don't trash argument contentsMichael Haggerty, Dec 31, 2016
  26. Jeff KingDec 31, 2016
  27. Michael HaggertyJan 2, 2017
  28. Jeff KingJan 2, 2017
  29. 22/23 try_remove_empty_parents(): teach to remove parents of reflogs, tooMichael Haggerty, Dec 31, 2016
  30. 21/23 try_remove_empty_parents(): don't accommodate consecutive slashesMichael Haggerty, Dec 31, 2016
  31. Junio C HamanoJan 1, 2017
  32. Jeff KingJan 1, 2017
  33. Michael HaggertyJan 2, 2017
  34. Jeff KingJan 2, 2017
  35. 23/23 files_transaction_commit(): clean up empty directoriesMichael Haggerty, Dec 31, 2016
  36. 04/23 safe_create_leading_directories(): set errno on SCLD_EXISTSMichael Haggerty, Dec 31, 2016
  37. 08/23 rename_tmp_log(): use raceproof_create_file()Michael Haggerty, Dec 31, 2016
  38. 14/23 log_ref_write_1(): don't depend on logfile argumentMichael Haggerty, Dec 31, 2016
  39. Jeff KingDec 31, 2016
  40. Michael HaggertyDec 31, 2016
  41. 17/23 delete_ref_loose(): derive loose reference path from lockMichael Haggerty, Dec 31, 2016
  42. 18/23 delete_ref_loose(): inline functionMichael Haggerty, Dec 31, 2016
  43. 09/23 rename_tmp_log(): improve error reportingMichael Haggerty, Dec 31, 2016
  44. 10/23 log_ref_write(): inline functionMichael Haggerty, Dec 31, 2016
  45. Junio C HamanoJan 1, 2017
  46. Michael HaggertyJan 1, 2017
  47. Jeff KingDec 31, 2016
  48. Junio C HamanoJan 1, 2017
  49. Jacob KellerJan 1, 2017
  50. Jacob KellerJan 1, 2017
  51. Philip OakleyJan 1, 2017
  52. Jacob KellerJan 1, 2017
  53. Jeff KingJan 2, 2017
  54. Michael HaggertyJan 2, 2017
  55. Jacob KellerJan 2, 2017

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