Calling constant functions that use msg.sender in non-constant functions fails

[fubuloubu]

I was testing some updates I was making with one of my example contracts and I think I may have stumbled upon a bug, or at least something I don't understand why it should fail (and it's not very clear why)

To summarize, I have a contract that contains a constant method to return the balance of some map (address -> record) for the address associated with the message sender. I decided to use this function in my other functions so I didn't duplicate this access in multiple spots, basically assuming that if I called this @constant function, the msg.sender attribute would be passed to that @constant function. However, when I do this I get the TransactionFailed exception from pyethereum.

Here's an example:

from ethereum.tools import tester
from viper import compiler

chain = tester.Chain()
tester.languages['viper'] = compiler.Compiler()
chain.head_state.gas_limit = 10**9

code="""
bal: num[address]

def __init__():
    self.bal[msg.sender] = 1

@constant
def get_my_bal() -> num:
    return self.bal[msg.sender]

def foo():
    assert self.bal[msg.sender] > 0

def bar():
    assert self.get_my_bal() > 0
"""

c = chain.contract(code, language='viper')
c.get_my_bal() # Works fine
c.foo() # Works fine as well
c.bar() # Fails with ethereum.tools.tester.TransactionFailed()

Please let me know if I am misunderstanding how the @constant is supposed to be used (I am assuming you should be allowed to call @constant functions from other functions) (I am also assuming that implicit values such as msg.sender are passed to @constant functions as well).

Not totally certain what the problem is...

[fubuloubu]

I believe that msg.sender and other "internal"quantities are not passed to an internal call to a function in a Viper program. Still trying to figure out why, would appreciate any help!

[DavidKnott]

@fubuloubu Great catch! I'll help with this, off the top of my head I'm guessing it's an issue with how function contexts are being made.

[fubuloubu]

I narrowed it down to a test case that we can use to debug. I'll create a pull request for that, and then maybe you can help me debug the issue further.

[fubuloubu]

Created #320

Further collaboration on that please.