runBlock gives less gasUsed than runTx

[asinyagin]

Hi,

As I see, runBlock() gives wrong gasUsed while runTx() uses correct number of gas. Here's how to reproduce it: https://github.com/asinyagin/ethereumjs-test/blob/master/app.js . The app prints:

root@982421ef3b07:~/ethereumjs-test# node app.js 
tx: 5a24e
block: 05254e

[axic]

Does runTx gives the correct number compared to geth/ethereumj? And do you see a consistent difference between the two when running with other examples or is random?

[asinyagin]

yeah, the live network uses the same number of gas as runTx

[axic]

The difference seems to be 32000 which is the cost of CREATE. There might be something off in block vs. tx regarding deploying a contract. Are you calling CREATE from your code?

cc @wanderer

[wanderer]

so to recap I bet this is also the creation cost of a precompiled. @axic added an option to active the precompiles @asinyagin can you give that a try?

[asinyagin]

@axic I'm not sure. That's Ballot contract from https://ethereum.github.io/browser-solidity/#version=soljson-latest.js compiled with solc 0.3.0 with constructor parameter 10.

[asinyagin]

@wanderer it gives the same gasUsed (the wrong one) with the key. Is the code correct? https://github.com/asinyagin/ethereumjs-test/blob/master/app.js#L37

[danfinlay]

I'm also experiencing out of gas errors, I think it may be related to this. Particularly, I'm getting OOG errors on transactions estimated by testrpc (which relies on ethereumjs-vm).

The bug is documented on the testrpc github here and includes a test case.

[danfinlay]

Even better and more specific reproduction steps in this testrpc issue, #96.

[kumavis]

playing out the repro here with some deeper logging trufflesuite/ganache-cli-archive#96
while the trace is exactly the same, the gas calc divergence can be seen near the end https://www.diffchecker.com/7w3djc6a
the logging is a little confusing... +3 is gas used, resulting number is remaining gas (limit - used)

some how 4683971-3 = 4663968 (off by 20000) but only in runBlock and not in estimateGas

wat

[wanderer]

@kumavis so its messing up on the SSTORE on line 148

[kumavis]

ah ok
somehow the dynamic cost is calc'd wrong

[kumavis]

© 2015 DiffChecker, Inc.

lel

[kumavis]

turns out my issue was unrelated -- was an issues in testrpc's provider-engine trufflesuite/ganache-cli-archive#96

[wanderer]

@asinyagin The problem is here https://github.com/asinyagin/ethereumjs-test/blob/master/app.js#L75 There is a cost difference between homestead and pre-homestead to create an account. By default tx's are homestead, but by setting the block number to 0 you force it to run as pre-homestead.

I added a check in 475143f that should fix teh problem if you give the VM the option opts:{enableHomestead: true}

[wanderer]

@asinyagin please reopen if this if its still an issue

[asinyagin]

@wanderer thanks! it works great