I am working on a self education project, where I am attempting to build a cheap miner application. I have set up "testnet in a box" and have written a small miner that builds version 2 blocks. The miner mines successfully, all blocks up to and including 127, but when attempting to submit block 128 blocks become rejected citing error "AcceptBlock() : block height mismatch in coinbase"

The coinbase script I am using looks like this: (example does not include the script length varint prefix)
0180 00002f503253482f04b8864e50080800000200000001072f736c7573682f



It is curious, how the block that fails is the one immediately past the max value of a signed byte (127) I suspect there may be a genuine bug here, related to how bitcoin computes the expected prefix.

Internally height is stored as a "signed" int: (Collected from AcceptBlock() function in main.cpp)
int nHeight = 0;

I suspect errors occur when these signed values get compacted into a variable integer. We may simply have never seen this, because of the possibility block version 2 was not introduced until both testnet and mainnet were sufficiently long to mask the problem. Sadly, I don't have the environment or tools set up to compile and rake around in bitcoin code. Can someone here more equipped, and more knowledgeable than I help me investigate this? I'd be curious of the result of the following snippit of code:

int nHeight = 128;
CScript expect = CScript() << nHeight;

See if the bytes built by CScript turn out to be "0180" as expected.


Thanks in advance!

Matt