Prob it works because it resets buffer but not sure, I'll try to add some tests here today evening

Prob it works because it resets buffer but not sure, I'll try to add some tests here today evening

Uhm, not sure. The writeAt() is called one extra time with the extra length 🤔

Agree, so I'm kinda not sure how it passed this test

I think I may have understood why no test was failing. The length was written twice, but both times at the same position, overwriting the alen (4 bytes) placeholder initially written by writeLabelIndexesOffsetTable(). The writeLabelIndexesOffsetTable() function initially writes 4 bytes placeholder, then the length is later written back in the position of the placeholder. Writing the length twice was overwriting the placeholder twice, which is superfluous but actually not a corruption bug.

Ah looks like you're right, it does w.write ... startPos, the same pos to write, so it re-write over and doesn't break anything, just writing 2 times

Even the written length should have been correct, because w.f.pos (used to compute the length as l := w.f.pos - startPos - 4) was not advanced by .writeAt() (the .Write() advances it, but not the WriteAt()).

Can you please point me in doc, becuase I can't find any piece of doc saying about updateing position. Just need that to learn

Can you please point me in doc, becuase I can't find any piece of doc saying about updateing position. Just need that to learn

My reasoning:

• The length of an index section is computed by l := w.f.pos - startPos - 4 (code)
• Before merging this PR we were computing the length twice. If w.f.pos changes between the 2 lines of code where we compute the length, then the 2nd length value would be corrupted.
• The length is written by calling w.writeAt() (code), so question is: does w.writeAt() increases w.f.pos or not? I don't think so, because pos is increased by FileWriter.Write() (code) but not by FileWriter.WriteAt() (code)

i see, interesting

Postmortem:
Where did we get lucky - we didn't broke anything yet, even bug was introduced =)

Thanks both for caring about this so much 👍