"Assertion `pindex->nCachedBranchId' failed" when trying to simulate a reorg

[cadaniluk]

For testing purposes I wanted to simulate a reorg on zcashd. What I am doing is essentially starting two nodes (0 denotes the first node, 1 the second), making them generate an unequal number of blocks, and then connecting them to see the shorter one reorg.
The full error I am getting on node 0 is

zcashd: main.cpp:2982: DisconnectResult DisconnectBlock(const CBlock &, CValidationState &, const CBlockIndex *,
CCoinsViewCache &, const CChainParams &, const bool): Assertion `pindex->nCachedBranchId' failed.

I started them like this:

Node 0: zcashd -debug -regtest -datadir=node0 -conf=zcash.conf -port=40000 -rpcport=50000 &
Node 1: zcashd -debug -regtest -datadir=node1 -conf=zcash.conf -port=40001 -rpcport=50001 &

In terms of RPC commands, this is what I did:

(Node 0 runs on 127.0.0.1:40000, node 1 on 127.0.0.1:40001.)

0: addnode 127.0.0.1:40001 add
0: generate 200                                      # shared base
0: disconnectnode 127.0.0.1:40001 
0: setban 127.0.0.1 add                        # prevent reconnection
0: generate 1                                          # short branch only on node 0
1: generate 2                                          # long branch only on node 1
0: clearbanned                                       # allow reconnection, triggering reorg on node 1

I also tried without 0: generate 200 to start from the Genesis block, the result is the same.

I would have expected to see some messages concerning the reorg and its result showing in 0: getchaintips. Node 0 crashes, however, because of the failed assertion.

I guess this is a bug since a user should not be able to trigger an assertion failure with RPC commands, but if I am doing something non-standard, tell me. Furthermore, could you suggest some workaround if this bug is not straightforward to fix, please?

Node 0's and node 1's debug.log files are attached.

Zcash version: v5.5.1

Machine specs:

• OS name + version: Fedora 37
• CPU: Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz
• Linux kernel version (uname -a): Linux *** 6.2.15-200.fc37.x86_64 Dust off codebase: build, run, poke at JSON api, try to exercise mint, pour, and receive manually. #1 SMP PREEMPT_DYNAMIC Thu May 11 15:56:33 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
• Compiler version (gcc --version): gcc (GCC) 12.3.1 20230508 (Red Hat 12.3.1-1)
• Linker version (ld -v): GNU ld version 2.38-27.fc37
• Assembler version (as --version): GNU assembler version 2.38-27.fc37

[miodragpop]

Network upgrades are not automatically activated in regtest mode. I think you should manually activate some (at least). For example, by adding -nuparams=76b809bb:1 to zcashd command line arguments for Sapling activation at height 1.