Merge #16572: wallet: Fix Char as Bool in Wallet

2dbfb37 Fix Char as Bool in interfaces (Jeremy Rubin)

Pull request description:

  In a few places in src/wallet/wallet.h, we use a char when semantically we want a bool.

  This is kind of an issue because it means we can unserialize the same transaction with different fFromMe flags (as differing chars) and evaluate the following section in wallet/wallet.cpp
  ```c++
          if (wtxIn.fFromMe && wtxIn.fFromMe != wtx.fFromMe)
           {
               wtx.fFromMe = wtxIn.fFromMe;
               fUpdated = true;
           }
  ```
  incorrectly (triggering an fUpdated where both fFromMe values represent true, via different chars).

  I don't think this is a vulnerability, but it's just a little messy and unsemantic, and could lead to issues with stored wtxIns not being findable in a map by their hash.

  The serialize/unserialize code for bool internally uses a char, so it should be safe to make this substitution.

  NOTE: Technically, this is a behavior change -- I haven't checked too closely that nowhere is depending on storing information in this char. Theoretically, this could break something because after this change a tx unserialized with such a char would preserve it's value, but now it is converted to a ~true~ canonical bool.

ACKs for top commit:
  achow101:
    Code review ACK 2dbfb37
  meshcollider:
    Code review ACK 2dbfb37

Tree-SHA512: 8c0dc9cf672aa2276c694facbf50febe7456eaa8bf2bd2504f81a61052264b8b30cdb5326e1936893adc3d33504667aee3c7e207a194c71d87b3e7b5fe199c9d

Author: fanquake

src/wallet/wallet.h

@@ -444,7 +444,7 @@ class CWalletTx
      * on this bitcoin node, and set to 0 for transactions that were created
      * externally and came in through the network or sendrawtransaction RPC.
      */
-    char fFromMe;
+    bool fFromMe;
     int64_t nOrderPos; //!< position in ordered transaction list
     std::multimap<int64_t, CWalletTx*>::const_iterator m_it_wtxOrdered;
 
@@ -501,8 +501,8 @@ class CWalletTx
 
         std::vector<char> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<char> dummy_vector2; //!< Used to be vtxPrev
-        char dummy_char = false; //!< Used to be fSpent
-        s << tx << hashBlock << dummy_vector1 << nIndex << dummy_vector2 << mapValueCopy << vOrderForm << fTimeReceivedIsTxTime << nTimeReceived << fFromMe << dummy_char;
+        bool dummy_bool = false; //!< Used to be fSpent
+        s << tx << hashBlock << dummy_vector1 << nIndex << dummy_vector2 << mapValueCopy << vOrderForm << fTimeReceivedIsTxTime << nTimeReceived << fFromMe << dummy_bool;
     }
 
     template<typename Stream>
@@ -512,8 +512,8 @@ class CWalletTx
 
         std::vector<uint256> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<CMerkleTx> dummy_vector2; //!< Used to be vtxPrev
-        char dummy_char; //! Used to be fSpent
-        s >> tx >> hashBlock >> dummy_vector1 >> nIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_char;
+        bool dummy_bool; //! Used to be fSpent
+        s >> tx >> hashBlock >> dummy_vector1 >> nIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_bool;
 
         ReadOrderPos(nOrderPos, mapValue);
         nTimeSmart = mapValue.count("timesmart") ? (unsigned int)atoi64(mapValue["timesmart"]) : 0;