Make DummySignatureCreator a singleton

Author: sipa

src/script/ismine.cpp

@@ -146,7 +146,7 @@ isminetype IsMine(const CKeyStore &keystore, const CScript& scriptPubKey, bool&
     if (keystore.HaveWatchOnly(scriptPubKey)) {
         // TODO: This could be optimized some by doing some work after the above solver
         SignatureData sigs;
-        return ProduceSignature(keystore, DummySignatureCreator(), scriptPubKey, sigs) ? ISMINE_WATCH_SOLVABLE : ISMINE_WATCH_UNSOLVABLE;
+        return ProduceSignature(keystore, DUMMY_SIGNATURE_CREATOR, scriptPubKey, sigs) ? ISMINE_WATCH_SOLVABLE : ISMINE_WATCH_UNSOLVABLE;
     }
     return ISMINE_NO;
 }

src/script/sign.cpp

@@ -392,54 +392,51 @@ SignatureData CombineSignatures(const CScript& scriptPubKey, const BaseSignature
 
 namespace {
 /** Dummy signature checker which accepts all signatures. */
-class DummySignatureChecker : public BaseSignatureChecker
+class DummySignatureChecker final : public BaseSignatureChecker
 {
 public:
     DummySignatureChecker() {}
+    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override { return true; }
+};
+const DummySignatureChecker DUMMY_CHECKER;
 
-    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override
+class DummySignatureCreator final : public BaseSignatureCreator {
+public:
+    DummySignatureCreator() {}
+    const BaseSignatureChecker& Checker() const override { return DUMMY_CHECKER; }
+    bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override
     {
+        // Create a dummy signature that is a valid DER-encoding
+        vchSig.assign(72, '\000');
+        vchSig[0] = 0x30;
+        vchSig[1] = 69;
+        vchSig[2] = 0x02;
+        vchSig[3] = 33;
+        vchSig[4] = 0x01;
+        vchSig[4 + 33] = 0x02;
+        vchSig[5 + 33] = 32;
+        vchSig[6 + 33] = 0x01;
+        vchSig[6 + 33 + 32] = SIGHASH_ALL;
         return true;
     }
 };
-const DummySignatureChecker dummyChecker;
-} // namespace
-
-const BaseSignatureChecker& DummySignatureCreator::Checker() const
-{
-    return dummyChecker;
 }
 
-bool DummySignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const
-{
-    // Create a dummy signature that is a valid DER-encoding
-    vchSig.assign(72, '\000');
-    vchSig[0] = 0x30;
-    vchSig[1] = 69;
-    vchSig[2] = 0x02;
-    vchSig[3] = 33;
-    vchSig[4] = 0x01;
-    vchSig[4 + 33] = 0x02;
-    vchSig[5 + 33] = 32;
-    vchSig[6 + 33] = 0x01;
-    vchSig[6 + 33 + 32] = SIGHASH_ALL;
-    return true;
-}
+const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR = DummySignatureCreator();
 
 bool IsSolvable(const SigningProvider& provider, const CScript& script)
 {
     // This check is to make sure that the script we created can actually be solved for and signed by us
     // if we were to have the private keys. This is just to make sure that the script is valid and that,
     // if found in a transaction, we would still accept and relay that transaction. In particular,
     // it will reject witness outputs that require signing with an uncompressed public key.
-    static const DummySignatureCreator creator;
     SignatureData sigs;
     // Make sure that STANDARD_SCRIPT_VERIFY_FLAGS includes SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, the most
     // important property this function is designed to test for.
     static_assert(STANDARD_SCRIPT_VERIFY_FLAGS & SCRIPT_VERIFY_WITNESS_PUBKEYTYPE, "IsSolvable requires standard script flags to include WITNESS_PUBKEYTYPE");
-    if (ProduceSignature(provider, creator, script, sigs)) {
+    if (ProduceSignature(provider, DUMMY_SIGNATURE_CREATOR, script, sigs)) {
         // VerifyScript check is just defensive, and should never fail.
-        assert(VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker()));
+        assert(VerifyScript(sigs.scriptSig, script, &sigs.scriptWitness, STANDARD_SCRIPT_VERIFY_FLAGS, DUMMY_CHECKER));
         return true;
     }
     return false;

src/script/sign.h

@@ -58,11 +58,7 @@ class MutableTransactionSignatureCreator : public TransactionSignatureCreator {
 };
 
 /** A signature creator that just produces 72-byte empty signatures. */
-class DummySignatureCreator : public BaseSignatureCreator {
-public:
-    const BaseSignatureChecker& Checker() const override;
-    bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
-};
+extern const BaseSignatureCreator& DUMMY_SIGNATURE_CREATOR;
 
 struct SignatureData {
     CScript scriptSig;

src/wallet/wallet.cpp

@@ -1535,7 +1535,7 @@ bool CWallet::DummySignInput(CTxIn &tx_in, const CTxOut &txout) const
     const CScript& scriptPubKey = txout.scriptPubKey;
     SignatureData sigdata;
 
-    if (!ProduceSignature(*this, DummySignatureCreator(), scriptPubKey, sigdata))
+    if (!ProduceSignature(*this, DUMMY_SIGNATURE_CREATOR, scriptPubKey, sigdata))
     {
         return false;
     } else {