Invalid memory address or nil pointer dereference on weird TxOut

[tsileo]

Hi,

I'm trying to parse the blockchain using gocoin, but I got a panic: runtime error: invalid memory address or nil pointer dereference when I try to decode address for weird TxOut.

Here is my code (https://gist.github.com/tsileo/8008319), and here is the exception I'm getting:

2013/12/17 17:56:54 128233
2013/12/17 17:56:54 128234
2013/12/17 17:56:54 128235
2013/12/17 17:56:54 128236
2013/12/17 17:56:54 128237
2013/12/17 17:56:54 128238
2013/12/17 17:56:54 128239
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x50 pc=0x44796a]

goroutine 1 [running]:
github.com/piotrnar/gocoin/btc.(*BtcAddr).String(0x0, 0x1a, 0x1a)
    /work/opensource/blockchain_playground_golang/src/github.com/piotrnar/gocoin/btc/addr.go:134 +0x2a
main.main()
    /work/opensource/blockchain_playground_golang/dat2.go:75 +0x250e

goroutine 2 [syscall]:
exit status 2

It happens on weird TxOut, when it can't decode/compute address, I found some explanations here and here.

I see it at block:

• 71036
• 127630
• 128239
• I stopped at block 128239

Even blockchain.info can't handle these TxOuts, I think it's missing some error checking, maybe it should return nil ?

I just started learning Go, so let me know if I missed something,

Thanks!

[piotrnar]

I think it is because you do this:

txo_addr = btc.NewAddrFromPkScript(txo.Pk_script, false).String()

btc.NewAddrFromPkScript() returns "nil" in certain cases and you unconditional call of the method String() there is causing the panic.

[tsileo]

My bad! You're right, thanks a lot!!!

[piotrnar]

Sure, no problem. Glad I could help.

[tsileo]

I just wanted to let you know I've written an article about parsing block chain raw blocks using Gocoin: http://thomassileo.com/blog/2013/12/17/parsing-the-bitcoin-block-chain-with-go-language-using-gocoin/.

Let me know if you have any feedback,

Thanks!