GetCallingScriptHash from module returns incorrect value about neo-boa

[igormcoelho]

I did some quick simulations with both Python and C#, and they seem to behave the same way. I expanded the test to include functions: GetCallingScriptHash(), GetEntryScriptHash() and GetExecutingScriptHash()

    caller = GetCallingScriptHash()
    caller2 = GetEntryScriptHash()
    caller3 = GetExecutingScriptHash()
contracts:
(A): #6edabfbf75265d2dd024416183f69aec677ee8e9
(B): # fb593745178a682d6df4dda9aa160af23d3444d4

#python
b'caller_main'
b'\xd4D4=\xf2\n\x16\xaa\xa9\xdd\xf4m-h\x8a\x17E7Y\xfb'  #b'd444343df20a16aaa9ddf46d2d688a17453759fb'
b'caller2_main'
b'v\xf1\xb4sZ\x9e\x0c\x8f\xb5\xb2s\xb8p\x10`\x1a\xcd\xa9\x04\xa9'  #b'76f1b4735a9e0c8fb5b273b87010601acda904a9'
b'caller3_main'
b'\xe9\xe8~g\xec\x9a\xf6\x83aA$\xd0-]&u\xbf\xbf\xdan' #b'e9e87e67ec9af683614124d02d5d2675bfbfda6e'
b'caller_printCaller'
b'\xe9\xe8~g\xec\x9a\xf6\x83aA$\xd0-]&u\xbf\xbf\xdan' #b'e9e87e67ec9af683614124d02d5d2675bfbfda6e'
b'caller2_printCaller'
b'v\xf1\xb4sZ\x9e\x0c\x8f\xb5\xb2s\xb8p\x10`\x1a\xcd\xa9\x04\xa9' #b'76f1b4735a9e0c8fb5b273b87010601acda904a9'
b'caller3_printCaller'
b'\xe9\xe8~g\xec\x9a\xf6\x83aA$\xd0-]&u\xbf\xbf\xdan' #b'e9e87e67ec9af683614124d02d5d2675bfbfda6e'

# C#
{"txid":"0x1ebc29295160470cede06e4e05008b850f1a321c46606862538e85ecc15ed352","vmstate":"HALT, BREAK","gas_consumed":"0.101","stack":[{"type":"ByteArray","value":""},
{"type":"ByteArray","value":""},{"type":"ByteArray","value":""}],
"notifications":[{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller_main"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"d444343df20a16aaa9ddf46d2d688a17453759fb"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller2_main"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"76f1b4735a9e0c8fb5b273b87010601acda904a9"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller3_main"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"e9e87e67ec9af683614124d02d5d2675bfbfda6e"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller_printCaller"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"e9e87e67ec9af683614124d02d5d2675bfbfda6e"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller2_printCaller"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"76f1b4735a9e0c8fb5b273b87010601acda904a9"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"caller3_printCaller"}},
{"contract":"0x6edabfbf75265d2dd024416183f69aec677ee8e9","state":{"type":"ByteArray","value":"e9e87e67ec9af683614124d02d5d2675bfbfda6e"}}]}

It seems the only way to get the right contract calling information is on Main scope (and store it for further usage). GetCallingScriptHash() seems to return the scriphash of the contract which performed the last CALL operation, while GetExecutingScriptHash() seems to be consistent.

[igormcoelho]

@nickfujita @localhuman That is the correct behavior.

Let's assume InvocationStack is currently:
0: 6edabfbf75265d2dd024416183f69aec677ee8e9 (ContractA)
1: fb593745178a682d6df4dda9aa160af23d3444d4 (ContractB)

CurrentContext (in GetExecutingScriptHash) is: 6edabfbf75265d2dd024416183f69aec677ee8e9 (ContractA). GetCallingScriptHash returns position 1 of InvocationStack: fb593745178a682d6df4dda9aa160af23d3444d4 (ContractB).

After you perform a (function) CALL: https://github.com/neo-project/neo-vm/blob/e2f3b1aa42073ce27343c9a95bf076ce7d19d787/src/neo-vm/ExecutionEngine.cs#L124
you clone CurrentContext and put on InvocationStack, which becomes:
0: 6edabfbf75265d2dd024416183f69aec677ee8e9 (ContractA)
1: 6edabfbf75265d2dd024416183f69aec677ee8e9 (ContractA)
2: fb593745178a682d6df4dda9aa160af23d3444d4 (ContractB)

So, GetCallingScriptHash will change value, and it is actually information that the contract itself performed the last CALL operation (not ContractB anymore).

[igormcoelho]

@shargon @vncoelho it is amazing that I got interested by this post (by chance), because it seems to break my idea of function CALL inlining in NeonOpt project, when people are using GetCallingScriptHash information... in fact, if @nickfujita used my function inliner, he wouldn't have had this issue, because auxiliar function would have been moved to main scope :D hahahah

[ixje]

@nickfujita unfortunately this is expected. I reported this issue some months ago here neo-project/neo-vm#29 and Erik Zhang said it's expected and intended behaviour.