bcli: Bitcoin backend assumes Linux-style newlines

[cdecker]

A user reported this error on [reddit]:

So I have confirmed that the bitcoin-cli.exe is being invoked, with the arguments shown. But I am not sure why this error is coming up. If I run bitcoin-cli.exe from command line, I can easily get replies for command like getblockchaininfo, which confirms that bitcoind is running.

Here is what I get as output of lightningd command:

2020-08-30T17:35:53.634Z INFO plugin-bcli: bitcoin-cli initialized and connected to bitcoind.
/usr/local/bin/../libexec/c-lightning/plugins/bcli error: bad response to getrawblockbyheight (bad 'result' field), response was {"jsonrpc":"2.0","id":8,"error":{"code":400,"message":"bitcoin-cli.exe -datadir=G:\\\\.bitcoin -rpcconnect=127.0.0.1 -rpcport=8332 -rpcuser=... -rpcpassword=... getblockhash 646000: bad JSON: bad blockhash (00000000000000000001ef19be9c9879c6e9aa6241a096f543109e2a34397936\r\n)"} }

Not sure why I am seeing this problem.

Update: I got it running. Now I see this

2020-08-30T23:45:47.611Z INFO plugin-bcli: bitcoin-cli initialized and connected to bitcoind.
2020-08-30T23:45:48.728Z INFO lightningd: --------------------------------------------------
2020-08-30T23:45:48.729Z INFO lightningd: Server started with public key 03c7505d1ac56441f234025cd348743cddff147f9356e6296820d5e95d1a56b29d, alias GREENTOLL (color #03c750) and lightningd v0.9.0-197-gdd8cd81-modded

I've no clue what I am doing, but will continue digging more.

From the datadir specified in the bitcoin-cli call it seems like this is
running on Windows (cygwin or MingW), and the error message seems to indicate
like it got a windows-style \r\n newline rather than the \n newline we
expect:

lightning/plugins/bcli.c

Lines 657 to 662 in 71e713c

	/* `-1` to strip the newline character. */
	stash->block_hash = tal_strndup(stash, bcli->output,
	bcli->output_bytes-1);
	if (!stash->block_hash || strlen(stash->block_hash) != 64) {
	return command_err_bcli_badjson(bcli, "bad blockhash");
	}

We should likely strip whitespace at the end in a more reliable fashion.