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Treat output length as a maximum length for CALL operations #236
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…new bytes to set was empty.
…t's a 0 length BytesValues rather than 32 bytes of zeross.
… actual data to output is shorter than outputLength, do not zero out the tail end of the memory range.
shemnon
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Nov 14, 2018
…ng#236) * Fix corner case where Memory did not clear target destination if the new bytes to set was empty. * Use BytesValue.EMPTY instead of Bytes32.EMPTY to make it clear that it's a 0 length BytesValues rather than 32 bytes of zeross. * Treat outputLength for call operations as a maximum length - when the actual data to output is shorter than outputLength, do not zero out the tail end of the memory range.
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PR description
For call-type operations when the output data is shorter than the specified output length, the extra unused memory should be left unchanged, not zeroed out. By chance Pantheon gets this right for the most common case when the output data is empty but not for other cases.
So fix the corner case in Memory so that it consistently zeros out all the memory in the range (which is the right behaviour for other operations like CODECOPY), then change
AbstractCallOperationto explicitly treat output length as a maximum length.New ethereum reference tests are being contributed to cover these cases: ethereum/tests#538
Issues with this behaviour were encountered on ropsten in block 1715984 and block 465128.