Testcase needed for CODECOPY where code_size=0

[masonforest]

We at Mana ran into a consensus breaking bug in our client at block #116524. The issue was that when code_size was set to 0 when running the opcode CODECOPY we would push a 0 onto the stack instead of leaving the state unchanged. This was a bug in our implementation and was fixed in commit mana-ethereum/mana@8279808. It may be helpful to add a test for this case for this so other new clients don’t run into the same issue in the future.

[holiman]

Looking at the fix, you mean CODECOPY, not CALLCODE, right?

[masonforest]

Whoops, yep. Updated 👍

[axic]

Can the new test case also cover EXTCODECOPY please?

[winsvega]

#569

could not really test codecopy of empty code. I've put codecopy into contract init code maybe this count.