using custom equal function in block_cache::cache_t #1264
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Crash happened again in internal tests, theory is wrong, I still think the PR is good |
aldenml
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Current coverage is 71.01% (diff: 100%)@@ master #1264 diff @@
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Files 391 391
Lines 58284 58283 -1
Methods 5756 5757 +1
Messages 0 0
Branches 8790 8790
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- Hits 41458 41389 -69
- Misses 12452 12516 +64
- Partials 4374 4378 +4
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I tracked all the locks on the mutex |
arvidn
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Oct 28, 2016
| , cached_piece_entry const& p2) const | ||
| { return p1.storage.get() == p2.storage.get() && p1.piece == p2.piece; } | ||
| }; | ||
| using cache_t = std::unordered_set<cached_piece_entry, hash_value, equal_value>; |
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I don't see how this is necessary. If it was, it would have been a compilation error. cached_piece_entry already has an operator== which does this.
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Oh, I looked for it...I guess I'm over thinking with the issue/crash
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I expect this to fix the issue #1225 (if not, well, need to keep looking).
The theory behind this is the following:
The custom hash is used to determine the internal bucket in the internal hash table. The
libc++implementation of thefind, lookup the bucket and iterate all the elements (it could be one) and test for equality of the value (default is the==). In this case, not providing a customequalsis a bug.Why it hasn't happened before? Looking at the
boost::unordered_setimplementation, branchRC_1_1, in theirfindalgorithm, they lookup the bucket and they "cleverly" returns if only one element is found. If the bucket contains more than one element (hash collision) then they iterate using the equality. In this case, not providing a customequalsis irrelevant, since by "definition", this is a set and hash values should not create a collision.