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| -rw-r--r-- | Notes/BugStories.txt | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Notes/BugStories.txt b/Notes/BugStories.txt new file mode 100644 index 00000000..0e2ca1dd --- /dev/null +++ b/Notes/BugStories.txt @@ -0,0 +1,26 @@ +2019-07-13: Sizeof mismatch +=========================== + +librustc takes ~20mins to recompile, and that's just one crate out of ~80 in rustc +- rustc failing on a consistency check +- Turn on debug logging, add more to find where things become inconsistent +- add assertion that a hashmap insert worked +- started crashing earlier (but same place) +- Print the map, item is there +- Start dumping hashes, they don't match +- Check equality of pre-hash values, they match +- Check input to hasher, don't see anything too odd +- Add more debug to make it easier to see the instance hashig +- Notice the difference, a pointer difference? +- Match the hash inputs to fields, find an odd pair with the `ty::Slice` type +- Start chasing it's Hash impl down, it's supposed to just hash the pointer + - Actual impl hashes two words, not just one + - The source code checks sizeof to pick between one/two word hashing + - But post-optimisation it's always picking two + - Turn off that optimisation and rebuild librustc, no change? +- Check libcore's metadata, it has the bug already (in the generic version?) +- Enable optimisation debug and rebuild libcore +- Oh look, `sizeof<*const T>` where `T: ?Sized` is returning 16 instead of returning "I don't know yet" + +<!-- vim: ft=markdown +--> |