Database panic

[cpacia]

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x38 pc=0x8b2abf]
goroutine 55 [running]:
github.com/gcash/bchd/database/ffldb.rollbackOnPanic(0xc001244c80)
	/home/chris/workspace/bchd/database/ffldb/db.go:1903 +0x77
panic(0xc5e180, 0x15ae830)
	/usr/lib/go-1.14/src/runtime/panic.go:969 +0x166
github.com/gcash/bchd/database/ffldb.(*blockStore).writeData(0xc00012a320, 0xc00da3b3a0, 0x4, 0x4, 0xd786aa, 0x11, 0x0, 0xd27660)
	/home/chris/workspace/bchd/database/ffldb/blockio.go:387 +0x4f
github.com/gcash/bchd/database/ffldb.(*blockStore).writeBlock(0xc00012a320, 0xc00f7d2000, 0xba747, 0xba747, 0x9e026, 0x0, 0x0, 0x0, 0x0)
	/home/chris/workspace/bchd/database/ffldb/blockio.go:433 +0x10a
github.com/gcash/bchd/database/ffldb.(*transaction).writePendingAndCommit(0xc001244c80, 0xc001244c80, 0xc0089d8b00)
	/home/chris/workspace/bchd/database/ffldb/db.go:1685 +0x41c
github.com/gcash/bchd/database/ffldb.(*transaction).Commit(0xc001244c80, 0x0, 0x0)
	/home/chris/workspace/bchd/database/ffldb/db.go:1758 +0x9d
github.com/gcash/bchd/database/ffldb.(*db).Update(0xc00007e000, 0xc0000a4ec0, 0x0, 0x0)
	/home/chris/workspace/bchd/database/ffldb/db.go:1970 +0x100
github.com/gcash/bchd/blockchain.(*BlockChain).maybeAcceptBlock(0xc000141c00, 0xc00cef3ae0, 0xc00d91a584, 0xc00deca9a0, 0x4, 0x0, 0x0, 0xca2eab670e0973db)
	/home/chris/workspace/bchd/blockchain/accept.go:55 +0x113
github.com/gcash/bchd/blockchain.(*BlockChain).ProcessBlock(0xc000141c00, 0xc00cef3ae0, 0xc000000004, 0xc002910000, 0x0, 0x0)
	/home/chris/workspace/bchd/blockchain/process.go:218 +0x27d
github.com/gcash/bchd/netsync.(*SyncManager).handleBlockMsg(0xc00029a300, 0xc0072cd780)
	/home/chris/workspace/bchd/netsync/manager.go:787 +0x227
github.com/gcash/bchd/netsync.(*SyncManager).blockHandler(0xc00029a300)
	/home/chris/workspace/bchd/netsync/manager.go:1436 +0x703
created by github.com/gcash/bchd/netsync.(*SyncManager).Start
	/home/chris/workspace/bchd/netsync/manager.go:1696 +0xd7

This panic stems from this line trying to write the height of the final block when moving to a new file. The reason for the panic is because curFile.file is nil.

https://github.com/gcash/bchd/blob/master/database/ffldb/blockio.go#L433

Later on in this function we have:

// Open the current file if needed.  This will typically only be the
// case when moving to the next file to write to or on initial database
// load.  However, it might also be the case if rollbacks happened after
// file writes started during a transaction commit.
if wc.curFile.file == nil {
	file, err := s.openWriteFileFunc(wc.curFileNum)
	if err != nil {
		return blockLocation{}, err
	}
	wc.curFile.file = file
}

It seems it may be possible that it's trying to load curFile.file before it was set. Possibly an edge case where the first block to be processed on startup is creating a new block file?

Duplicating the above code block right before L433 appears to have got past the error though it's unclear if this is correct code wise.

[zquestz]

You going to put up a PR with your fix?

[cpacia]

yeah

[zquestz]

Any progress on this?