Merge #14094: refactoring: Remove unreferenced local variables

8ecaee1 Increase signal to noise in appveyor build output by reducing the MSVC warning count from 12 to 4 (12 is assuming the changes in #14086 are also implemented). (practicalswift)

Pull request description:

  Remove unreferenced local variables:

  Increase signal to noise in appveyor build output by reducing the MSVC warning count from 12 to 4. 12 is the number of MSVC warnings under our current appveyor setup assuming the changes in #14086 are also implemented.

  This makes it easier to spot errors or more important warnings in the verbose appveyor output. MSVC warnings are good, so having access to them in a noise free way (read: without trivial warnings) via appveyor without having to use Windows is really valuable.

  See #14086 (comment) plus discussion for context.

  Before:

  ```
  c:\projects\bitcoin\src\script\script.cpp(272): warning C4018: '>': signed/unsigned mismatch [C:\projects\bitcoin\build_msvc\libbitcoinconsensus\libbitcoinconsensus.vcxproj]
  c:\projects\bitcoin\src\rest.cpp(467): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\libbitcoin_server\libbitcoin_server.vcxproj]
  c:\projects\bitcoin\src\test\allocator_tests.cpp(147): warning C4312: 'reinterpret_cast': conversion from 'int' to 'void *' of greater size [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\coins_tests.cpp(511): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\coins_tests.cpp(524): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\coins_tests.cpp(722): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\coins_tests.cpp(783): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\crypto_tests.cpp(535): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?) [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\dbwrapper_tests.cpp(265): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\net_tests.cpp(118): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\net_tests.cpp(151): warning C4101: 'e': unreferenced local variable [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\scheduler_tests.cpp(57): warning C4305: 'argument': truncation from 'int' to 'bool' [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  ```

  After:

  ```
  c:\projects\bitcoin\src\script\script.cpp(272): warning C4018: '>': signed/unsigned mismatch [C:\projects\bitcoin\build_msvc\libbitcoinconsensus\libbitcoinconsensus.vcxproj]
  c:\projects\bitcoin\src\test\allocator_tests.cpp(147): warning C4312: 'reinterpret_cast': conversion from 'int' to 'void *' of greater size [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\crypto_tests.cpp(535): warning C4334: '<<': result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?) [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  c:\projects\bitcoin\src\test\scheduler_tests.cpp(57): warning C4305: 'argument': truncation from 'int' to 'bool' [C:\projects\bitcoin\build_msvc\test_bitcoin\test_bitcoin.vcxproj]
  ```

Tree-SHA512: 5051134126c570b8421d57c710f1f1b977600398d2b5e69f8a8bd766b3696f992bf4e3459643b99a6b7e08dee1adc92985ee4d0d52b20755954415cb6f23f2fb

src/rest.cpp

@@ -464,7 +464,7 @@ static bool rest_getutxos(HTTPRequest* req, const std::string& strURIPart)
                 oss >> fCheckMemPool;
                 oss >> vOutPoints;
             }
-        } catch (const std::ios_base::failure& e) {
+        } catch (const std::ios_base::failure&) {
             // abort in case of unreadable binary data
             return RESTERR(req, HTTP_BAD_REQUEST, "Parse error");
         }

src/test/coins_tests.cpp

@@ -508,7 +508,7 @@ BOOST_AUTO_TEST_CASE(ccoins_serialization)
         Coin cc4;
         ss4 >> cc4;
         BOOST_CHECK_MESSAGE(false, "We should have thrown");
-    } catch (const std::ios_base::failure& e) {
+    } catch (const std::ios_base::failure&) {
     }
 
     // Very large scriptPubKey (3*10^9 bytes) past the end of the stream
@@ -521,7 +521,7 @@ BOOST_AUTO_TEST_CASE(ccoins_serialization)
         Coin cc5;
         ss5 >> cc5;
         BOOST_CHECK_MESSAGE(false, "We should have thrown");
-    } catch (const std::ios_base::failure& e) {
+    } catch (const std::ios_base::failure&) {
     }
 }
 
@@ -719,7 +719,7 @@ static void CheckAddCoinBase(CAmount base_value, CAmount cache_value, CAmount mo
         test.cache.AddCoin(OUTPOINT, Coin(std::move(output), 1, coinbase), coinbase);
         test.cache.SelfTest();
         GetCoinsMapEntry(test.cache.map(), result_value, result_flags);
-    } catch (std::logic_error& e) {
+    } catch (std::logic_error&) {
         result_value = FAIL;
         result_flags = NO_ENTRY;
     }
@@ -780,7 +780,7 @@ void CheckWriteCoins(CAmount parent_value, CAmount child_value, CAmount expected
         WriteCoinsViewEntry(test.cache, child_value, child_flags);
         test.cache.SelfTest();
         GetCoinsMapEntry(test.cache.map(), result_value, result_flags);
-    } catch (std::logic_error& e) {
+    } catch (std::logic_error&) {
         result_value = FAIL;
         result_flags = NO_ENTRY;
     }

src/test/dbwrapper_tests.cpp

@@ -262,7 +262,7 @@ struct StringContentsSerializer {
                 try {
                     READWRITE(c);
                     str.push_back(c);
-                } catch (const std::ios_base::failure& e) {
+                } catch (const std::ios_base::failure&) {
                     break;
                 }
             }

src/test/net_tests.cpp

@@ -115,7 +115,7 @@ BOOST_AUTO_TEST_CASE(caddrdb_read)
         unsigned char pchMsgTmp[4];
         ssPeers1 >> pchMsgTmp;
         ssPeers1 >> addrman1;
-    } catch (const std::exception& e) {
+    } catch (const std::exception&) {
         exceptionThrown = true;
     }
 
@@ -148,7 +148,7 @@ BOOST_AUTO_TEST_CASE(caddrdb_read_corrupted)
         unsigned char pchMsgTmp[4];
         ssPeers1 >> pchMsgTmp;
         ssPeers1 >> addrman1;
-    } catch (const std::exception& e) {
+    } catch (const std::exception&) {
         exceptionThrown = true;
     }
     // Even through de-serialization failed addrman is not left in a clean state.

src/wallet/rpcwallet.cpp

@@ -278,7 +278,6 @@ static UniValue setlabel(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
     }
 
-    std::string old_label = pwallet->mapAddressBook[dest].name;
     std::string label = LabelFromValue(request.params[1]);
 
     if (IsMine(*pwallet, dest)) {