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Postings from December 2012
On 14 December 2012 14:16, Dave Mitchell <davem@iabyn.com> wrote: > On Thu, Dec 13, 2012 at 11:09:40PM -0800, Andreas J. Koenig via RT wrote: >> I have no bisect for this one because the test result is random: >> sometimes OK, sometimes SEGV. I saw it the first time happen with >> v5.17.6-281-g01f4497. The test script that triggered it was >> t/010_internals/100_threads.t. I just ran the test with v5.17.6 a >> hundred times without crash, so I suppose the problem stems from some >> commit after that. > > Given that its crashing while freeing a hash, perhaps the randomness of > the crash is related to the new hash randomisation. In which case you > could run it with the env var PERL_HASH_SEED_DEBUG=1, then when it > crashes, note the hash seed that was displayed at start up: > > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0xd460791e > > and then use that seed for the bisect: > > PERL_HASH_SEED=d460791e ./perl ... > > > Although Yves, I've just noticed that this seems to be a bit buggy: Actually no. The output here is as expected. Although maybe this hasnt been properly documented. See the delta for 5.17.6 for the documentation I did do. Ill try to improve the docs. But basically the seed is populated from the left, and omitted bits default to 0. This was done to make it easier to handle to arbitrary seed sizes. IOW, it isnt a number, its a string in hex. Consider that Siphash uses two 64 bit seeds, and other hash functions could have an arbitrary number of bits in their seeds. I have played around with hash functions that use very large "seeds". > $ PERL_HASH_SEED=1 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 > > $ PERL_HASH_SEED=0x1 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x00000000 Perhaps we should warn that we encountered an unexpected non-hex digit in this case. > $ PERL_HASH_SEED=f PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0xf0000000 > > $ PERL_HASH_SEED=100 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 > > $ PERL_HASH_SEED=10000 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 > > $ PERL_HASH_SEED=1000000 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 > > $ PERL_HASH_SEED=10000000 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 > > $ PERL_HASH_SEED=100000000 PERL_HASH_SEED_DEBUG=1 p -e 1 > HASH_FUNCTION = ONE_AT_A_TIME HASH_SEED = 0x10000000 -- perl -Mre=debug -e "/just|another|perl|hacker/"Thread Previous | Thread Next