I am having trouble understanding the function confirmAndCheck (line 149 in the Wallet contract). Pasting the code below, with my addition in the last line:

function confirmAndCheck(bytes32 _operation) internal returns (bool) {
        // determine what index the present sender is:
        uint ownerIndex = m_ownerIndex[uint(msg.sender)];
        // make sure they're an owner
        if (ownerIndex == 0) return;

        var pending = m_pending[_operation];
        // if we're not yet working on this operation, switch over and reset the confirmation status.
        if (pending.yetNeeded == 0) {
            // reset count of confirmations needed.
            pending.yetNeeded = m_required;
            // reset which owners have confirmed (none) - set our bitmap to 0.
            pending.ownersDone = 0;
            pending.index = m_pendingIndex.length++;
            m_pendingIndex[pending.index] = _operation;
        // determine the bit to set for this owner.
        uint ownerIndexBit = 2**ownerIndex;
        // make sure we (the message sender) haven't confirmed this operation previously.
        if (pending.ownersDone & ownerIndexBit == 0) {
            Confirmation(msg.sender, _operation);
            // ok - check if count is enough to go ahead.
            if (pending.yetNeeded <= 1) {
                // enough confirmations: reset and run interior.
                delete m_pendingIndex[m_pending[_operation].index];
                delete m_pending[_operation];
                return true;
                // not enough: record that this owner in particular confirmed.
                pending.ownersDone |= ownerIndexBit;
                // m_pending[_operation] = pending; // ?

In case of multiple confirmations, shouldn't we save the local variable pending inside m_pending, since it will be accessed again later in line 155?


1 Answer 1


It’s a reference type, so we shouldn’t.

On the other hand, assignments from a memory stored reference type to another memory-stored reference type does not create a copy.

Since the variable pending is reference, all changes applied to this variable are also applied to the origin. Therefore we don’t have to assign its value back to m_pending.

  • 1
    This answer has severe formatting or content problems. This answer is unlikely to be salvageable through editing, and might need to be removed.
    – niksmac
    Jan 26, 2017 at 2:08
  • @niksmac What’s the problem? Jan 26, 2017 at 9:38
  • Link only answers are generally not welcome, will get removed eventually.
    – niksmac
    Jan 26, 2017 at 9:40
  • Consider adding some information the link into this answer.
    – niksmac
    Jan 26, 2017 at 9:41
  • @niksmac Is it ok now? Jan 26, 2017 at 12:05

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