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Re: [PATCH 2/9] commit-graph: stop using signed integers to count bloom filters

From
Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Date
Aug 6, 2025, 12:54 UTC
Message-ID
<aJNQm1r_FOIqsDlZ@ugly>
In-Reply-To
<aJL06Nlee6CR-KK0@pks.im>
On Wed, Aug 06, 2025 at 08:23:36AM +0200, Patrick Steinhardt wrote:
Show 27 quoted lines
>On Mon, Aug 04, 2025 at 05:44:06PM -0400, Taylor Blau wrote:
>> I wrote these counters in 312cff5207 (bloom: split 
>> 'get_bloom_filter()'
>> in two, 2020-09-16) and 59f0d5073f (bloom: encode out-of-bounds filters
>> as non-empty, 2020-09-17), and I don't see a compelling reason that
>> these should be unsigned.
>
>I think that is going backwards though: the question to ask is why
>should these be signed if they cannot ever be negative?
>
>> It's true that we don't have any need for negative values here since we
>> are counting from zero, but I don't think that alone justifies changing
>> the signed-ness here.
>> 
>> Is there a reason beyond "these are always non-negative" that changing
>> the signed-ness is warranted? If so, let's discuss that and make sure
>> that it is documented in the commit message. If not, I think we could
>> drop this patch (and optionally the patch before it as well).
>
>Yes, there is: it makes code easier to reason about for the reader, and
>it means that we don't have to guard ourselves against negative values.
>
>If I see a counting variable that is signed I immediately jump to the
>question of whether or not it can ever be a negative value. I assume
>that the author of this code _intentfully_ made it signed to cater to a
>specific edge case.
>

well, there is also the diametrically opposed view: https://google.github.io/styleguide/cppguide.html#Integer_Types https://critical.eschertech.com/2010/04/07/danger-unsigned-types-used-here/ https://soundsoftware.ac.uk/c-pitfall-unsigned https://stackoverflow.com/questions/30395205/why-are-unsigned-integers-error-prone ..

in isync, i standardized on unsigned where possible (e2d3b4d55), and sure enough, i introduced one of those underflow bugs not much later (859b7dd7f => 12e30ce56) ...

Previous: Patrick SteinhardtNext: Junio C Hamano
Message 10 of 69 in “commit-graph: remove reliance on global state”
  1. 0/9 commit-graph: remove reliance on global statePatrick Steinhardt, Aug 4, 2025
  2. 1/9 trace2: introduce function to trace unsigned integersPatrick Steinhardt, Aug 4, 2025
  3. Taylor BlauAug 4, 2025
  4. 2/9 commit-graph: stop using signed integers to count bloom filtersPatrick Steinhardt, Aug 4, 2025
  5. Oswald BuddenhagenAug 4, 2025
  6. Patrick SteinhardtAug 4, 2025
  7. Junio C HamanoAug 4, 2025
  8. Taylor BlauAug 4, 2025
  9. Patrick SteinhardtAug 6, 2025
  10. Oswald BuddenhagenAug 6, 2025
  11. Junio C HamanoAug 6, 2025
  12. Junio C HamanoAug 6, 2025
  13. Patrick SteinhardtAug 7, 2025
  14. Junio C HamanoAug 7, 2025
  15. Patrick SteinhardtAug 11, 2025
  16. Junio C HamanoAug 5, 2025
  17. Taylor BlauAug 4, 2025
  18. 3/9 commit-graph: fix type for some write optionsPatrick Steinhardt, Aug 4, 2025
  19. Taylor BlauAug 4, 2025
  20. 4/9 commit-graph: fix sign comparison warningsPatrick Steinhardt, Aug 4, 2025
  21. Taylor BlauAug 4, 2025
  22. Patrick SteinhardtAug 6, 2025
  23. 5/9 commit-graph: stop using `the_hash_algo` via macrosPatrick Steinhardt, Aug 4, 2025
  24. Taylor BlauAug 4, 2025
  25. 6/9 commit-graph: store the hash algorithm instead of its lengthPatrick Steinhardt, Aug 4, 2025
  26. Taylor BlauAug 4, 2025
  27. 7/9 commit-graph: stop using `the_hash_algo`Patrick Steinhardt, Aug 4, 2025
  28. Taylor BlauAug 4, 2025
  29. Patrick SteinhardtAug 6, 2025
  30. 8/9 commit-graph: stop using `the_repository`Patrick Steinhardt, Aug 4, 2025
  31. Taylor BlauAug 4, 2025
  32. 9/9 commit-graph: stop passing in redundant repositoryPatrick Steinhardt, Aug 4, 2025
  33. Derrick StoleeAug 5, 2025
  34. Patrick SteinhardtAug 6, 2025
  35. 00/10 commit-graph: remove reliance on global statePatrick Steinhardt, Aug 6, 2025
  36. 01/10 trace2: introduce function to trace unsigned integersPatrick Steinhardt, Aug 6, 2025
  37. 02/10 commit-graph: stop using signed integers to count Bloom filtersPatrick Steinhardt, Aug 6, 2025
  38. 03/10 commit-graph: fix type for some write optionsPatrick Steinhardt, Aug 6, 2025
  39. Oswald BuddenhagenAug 6, 2025
  40. Junio C HamanoAug 6, 2025
  41. Patrick SteinhardtAug 7, 2025
  42. 04/10 commit-graph: fix sign comparison warningsPatrick Steinhardt, Aug 6, 2025
  43. 05/10 commit-graph: stop using `the_hash_algo` via macrosPatrick Steinhardt, Aug 6, 2025
  44. 06/10 commit-graph: store the hash algorithm instead of its lengthPatrick Steinhardt, Aug 6, 2025
  45. 07/10 commit-graph: refactor `parse_commit_graph()` to take a repositoryPatrick Steinhardt, Aug 6, 2025
  46. 08/10 commit-graph: stop using `the_hash_algo`Patrick Steinhardt, Aug 6, 2025
  47. 09/10 commit-graph: stop using `the_repository`Patrick Steinhardt, Aug 6, 2025
  48. 10/10 commit-graph: stop passing in redundant repositoryPatrick Steinhardt, Aug 6, 2025
  49. 00/10 commit-graph: remove reliance on global statePatrick Steinhardt, Aug 7, 2025
  50. 01/10 trace2: introduce function to trace unsigned integersPatrick Steinhardt, Aug 7, 2025
  51. 02/10 commit-graph: stop using signed integers to count Bloom filtersPatrick Steinhardt, Aug 7, 2025
  52. 03/10 commit-graph: fix type for some write optionsPatrick Steinhardt, Aug 7, 2025
  53. Junio C HamanoAug 7, 2025
  54. Patrick SteinhardtAug 11, 2025
  55. 04/10 commit-graph: fix sign comparison warningsPatrick Steinhardt, Aug 7, 2025
  56. 05/10 commit-graph: stop using `the_hash_algo` via macrosPatrick Steinhardt, Aug 7, 2025
  57. 06/10 commit-graph: store the hash algorithm instead of its lengthPatrick Steinhardt, Aug 7, 2025
  58. 07/10 commit-graph: refactor `parse_commit_graph()` to take a repositoryPatrick Steinhardt, Aug 7, 2025
  59. 08/10 commit-graph: stop using `the_hash_algo`Patrick Steinhardt, Aug 7, 2025
  60. 09/10 commit-graph: stop using `the_repository`Patrick Steinhardt, Aug 7, 2025
  61. 10/10 commit-graph: stop passing in redundant repositoryPatrick Steinhardt, Aug 7, 2025
  62. 0/6 commit-graph: remove reliance on global statePatrick Steinhardt, Aug 15, 2025
  63. 1/6 commit-graph: stop using `the_hash_algo` via macrosPatrick Steinhardt, Aug 15, 2025
  64. 2/6 commit-graph: store the hash algorithm instead of its lengthPatrick Steinhardt, Aug 15, 2025
  65. 3/6 commit-graph: refactor `parse_commit_graph()` to take a repositoryPatrick Steinhardt, Aug 15, 2025
  66. 4/6 commit-graph: stop using `the_hash_algo`Patrick Steinhardt, Aug 15, 2025
  67. 5/6 commit-graph: stop using `the_repository`Patrick Steinhardt, Aug 15, 2025
  68. 6/6 commit-graph: stop passing in redundant repositoryPatrick Steinhardt, Aug 15, 2025
  69. Derrick StoleeAug 15, 2025

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