Merge bitcoin/bitcoin#28127: refactor: Remove C-style const-violating cast, Use reinterpret_cast

fa9108f85afdc926fd6a8b96cc2acff7ca25d7a8 refactor: Use reinterpret_cast where appropriate (MarcoFalke)
3333f950d49f13662842650ae76599a0dff052eb refactor: Avoid casting away constness (MarcoFalke)
fa6394dd10ae71755e46fd523dd43c2a1f2b832d refactor: Remove unused C-style casts (MarcoFalke)

Pull request description:

  Using a C-style cast to convert pointer types to a byte-like pointer type has many issues:

  * It may accidentally and silently throw away `const`.
  * It forces reviewers to check that it doesn't accidentally throw away `const`.

  For example, on current master a `const char*` is cast to `unsigned char*` (without `const`), see https://github.com/bitcoin/bitcoin/blob/d23fda05842ba4539b225bbab01b94df0060f697/src/span.h#L273 . This can lead to UB, and the only reason why it didn't lead to UB is because the return type added back the `const`. (Obviously this would break if the return type was deduced via `auto`)

  Fix all issues by adding back the `const` and using `reinterpret_cast` where appropriate.

ACKs for top commit:
  darosior:
    re-utACK fa9108f85afdc926fd6a8b96cc2acff7ca25d7a8
  hebasto:
    re-ACK fa9108f85afdc926fd6a8b96cc2acff7ca25d7a8.
  john-moffett:
    ACK fa9108f85afdc926fd6a8b96cc2acff7ca25d7a8

Tree-SHA512: 87f6e4b574f9bd96d4e0f2a0631fd0a9dc6096e5d4f1b95042fe9f197afc2fe9a24e333aeb34fed11feefcdb184a238fe1ea5aff10d580bb18d76bfe48b76a10

5 files changed, 55 insertions, 53 deletions

diff --git a/src/crypto/common.h b/src/crypto/common.h
index dc12ed9942..6ae5d4cd24 100644
--- a/src/crypto/common.h
+++ b/src/crypto/common.h
@@ -17,73 +17,73 @@
 uint16_t static inline ReadLE16(const unsigned char* ptr)
 {
     uint16_t x;
-    memcpy((char*)&x, ptr, 2);
+    memcpy(&x, ptr, 2);
     return le16toh(x);
 }
 
 uint32_t static inline ReadLE32(const unsigned char* ptr)
 {
     uint32_t x;
-    memcpy((char*)&x, ptr, 4);
+    memcpy(&x, ptr, 4);
     return le32toh(x);
 }
 
 uint64_t static inline ReadLE64(const unsigned char* ptr)
 {
     uint64_t x;
-    memcpy((char*)&x, ptr, 8);
+    memcpy(&x, ptr, 8);
     return le64toh(x);
 }
 
 void static inline WriteLE16(unsigned char* ptr, uint16_t x)
 {
     uint16_t v = htole16(x);
-    memcpy(ptr, (char*)&v, 2);
+    memcpy(ptr, &v, 2);
 }
 
 void static inline WriteLE32(unsigned char* ptr, uint32_t x)
 {
     uint32_t v = htole32(x);
-    memcpy(ptr, (char*)&v, 4);
+    memcpy(ptr, &v, 4);
 }
 
 void static inline WriteLE64(unsigned char* ptr, uint64_t x)
 {
     uint64_t v = htole64(x);
-    memcpy(ptr, (char*)&v, 8);
+    memcpy(ptr, &v, 8);
 }
 
 uint16_t static inline ReadBE16(const unsigned char* ptr)
 {
     uint16_t x;
-    memcpy((char*)&x, ptr, 2);
+    memcpy(&x, ptr, 2);
     return be16toh(x);
 }
 
 uint32_t static inline ReadBE32(const unsigned char* ptr)
 {
     uint32_t x;
-    memcpy((char*)&x, ptr, 4);
+    memcpy(&x, ptr, 4);
     return be32toh(x);
 }
 
 uint64_t static inline ReadBE64(const unsigned char* ptr)
 {
     uint64_t x;
-    memcpy((char*)&x, ptr, 8);
+    memcpy(&x, ptr, 8);
     return be64toh(x);
 }
 
 void static inline WriteBE32(unsigned char* ptr, uint32_t x)
 {
     uint32_t v = htobe32(x);
-    memcpy(ptr, (char*)&v, 4);
+    memcpy(ptr, &v, 4);
 }
 
 void static inline WriteBE64(unsigned char* ptr, uint64_t x)
 {
     uint64_t v = htobe64(x);
-    memcpy(ptr, (char*)&v, 8);
+    memcpy(ptr, &v, 8);
 }
 
 /** Return the smallest number n such that (x >> n) == 0 (or 64 if the highest bit in x is set. */
diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index 35782edca6..4ae2106211 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -54,6 +54,8 @@ struct DBParams {
     DBOptions options{};
 };
 
+inline auto CharCast(const std::byte* data) { return reinterpret_cast<const char*>(data); }
+
 class dbwrapper_error : public std::runtime_error
 {
 public:
@@ -113,12 +115,12 @@ public:
     {
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey((const char*)ssKey.data(), ssKey.size());
+        leveldb::Slice slKey(CharCast(ssKey.data()), ssKey.size());
 
         ssValue.reserve(DBWRAPPER_PREALLOC_VALUE_SIZE);
         ssValue << value;
         ssValue.Xor(dbwrapper_private::GetObfuscateKey(parent));
-        leveldb::Slice slValue((const char*)ssValue.data(), ssValue.size());
+        leveldb::Slice slValue(CharCast(ssValue.data()), ssValue.size());
 
         batch.Put(slKey, slValue);
         // LevelDB serializes writes as:
@@ -138,7 +140,7 @@ public:
     {
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey((const char*)ssKey.data(), ssKey.size());
+        leveldb::Slice slKey(CharCast(ssKey.data()), ssKey.size());
 
         batch.Delete(slKey);
         // LevelDB serializes erases as:
@@ -177,7 +179,7 @@ public:
         DataStream ssKey{};
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey((const char*)ssKey.data(), ssKey.size());
+        leveldb::Slice slKey(CharCast(ssKey.data()), ssKey.size());
         piter->Seek(slKey);
     }
 
@@ -265,7 +267,7 @@ public:
         DataStream ssKey{};
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey((const char*)ssKey.data(), ssKey.size());
+        leveldb::Slice slKey(CharCast(ssKey.data()), ssKey.size());
 
         std::string strValue;
         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
@@ -307,7 +309,7 @@ public:
         DataStream ssKey{};
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
-        leveldb::Slice slKey((const char*)ssKey.data(), ssKey.size());
+        leveldb::Slice slKey(CharCast(ssKey.data()), ssKey.size());
 
         std::string strValue;
         leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
@@ -351,8 +353,8 @@ public:
         ssKey2.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey1 << key_begin;
         ssKey2 << key_end;
-        leveldb::Slice slKey1((const char*)ssKey1.data(), ssKey1.size());
-        leveldb::Slice slKey2((const char*)ssKey2.data(), ssKey2.size());
+        leveldb::Slice slKey1(CharCast(ssKey1.data()), ssKey1.size());
+        leveldb::Slice slKey2(CharCast(ssKey2.data()), ssKey2.size());
         uint64_t size = 0;
         leveldb::Range range(slKey1, slKey2);
         pdb->GetApproximateSizes(&range, 1, &size);
diff --git a/src/span.h b/src/span.h
index 0563556dc2..7209d21a58 100644
--- a/src/span.h
+++ b/src/span.h
@@ -5,10 +5,10 @@
 #ifndef BITCOIN_SPAN_H
 #define BITCOIN_SPAN_H
 
-#include <type_traits>
-#include <cstddef>
 #include <algorithm>
-#include <assert.h>
+#include <cassert>
+#include <cstddef>
+#include <type_traits>
 
 #ifdef DEBUG
 #define CONSTEXPR_IF_NOT_DEBUG
@@ -267,10 +267,10 @@ Span<std::byte> MakeWritableByteSpan(V&& v) noexcept
 }
 
 // Helper functions to safely cast to unsigned char pointers.
-inline unsigned char* UCharCast(char* c) { return (unsigned char*)c; }
+inline unsigned char* UCharCast(char* c) { return reinterpret_cast<unsigned char*>(c); }
 inline unsigned char* UCharCast(unsigned char* c) { return c; }
-inline unsigned char* UCharCast(std::byte* c) { return (unsigned char*)c; }
-inline const unsigned char* UCharCast(const char* c) { return (unsigned char*)c; }
+inline unsigned char* UCharCast(std::byte* c) { return reinterpret_cast<unsigned char*>(c); }
+inline const unsigned char* UCharCast(const char* c) { return reinterpret_cast<const unsigned char*>(c); }
 inline const unsigned char* UCharCast(const unsigned char* c) { return c; }
 inline const unsigned char* UCharCast(const std::byte* c) { return reinterpret_cast<const unsigned char*>(c); }
 
diff --git a/src/test/argsman_tests.cpp b/src/test/argsman_tests.cpp
index 0b789e7f5c..1f46efe464 100644
--- a/src/test/argsman_tests.cpp
+++ b/src/test/argsman_tests.cpp
@@ -112,7 +112,7 @@ public:
         test.SetupArgs({{"-value", flags}});
         const char* argv[] = {"ignored", arg};
         std::string error;
-        bool success = test.ParseParameters(arg ? 2 : 1, (char**)argv, error);
+        bool success = test.ParseParameters(arg ? 2 : 1, argv, error);
 
         BOOST_CHECK_EQUAL(test.GetSetting("-value").write(), expect.setting.write());
         auto settings_list = test.GetSettingsList("-value");
@@ -217,13 +217,13 @@ BOOST_AUTO_TEST_CASE(util_ParseParameters)
     std::string error;
     LOCK(testArgs.cs_args);
     testArgs.SetupArgs({a, b, ccc, d});
-    BOOST_CHECK(testArgs.ParseParameters(0, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(0, argv_test, error));
     BOOST_CHECK(testArgs.m_settings.command_line_options.empty() && testArgs.m_settings.ro_config.empty());
 
-    BOOST_CHECK(testArgs.ParseParameters(1, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(1, argv_test, error));
     BOOST_CHECK(testArgs.m_settings.command_line_options.empty() && testArgs.m_settings.ro_config.empty());
 
-    BOOST_CHECK(testArgs.ParseParameters(7, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(7, argv_test, error));
     // expectation: -ignored is ignored (program name argument),
     // -a, -b and -ccc end up in map, -d ignored because it is after
     // a non-option argument (non-GNU option parsing)
@@ -248,17 +248,17 @@ BOOST_AUTO_TEST_CASE(util_ParseInvalidParameters)
 
     const char* argv[] = {"ignored", "-registered"};
     std::string error;
-    BOOST_CHECK(test.ParseParameters(2, (char**)argv, error));
+    BOOST_CHECK(test.ParseParameters(2, argv, error));
     BOOST_CHECK_EQUAL(error, "");
 
     argv[1] = "-unregistered";
-    BOOST_CHECK(!test.ParseParameters(2, (char**)argv, error));
+    BOOST_CHECK(!test.ParseParameters(2, argv, error));
     BOOST_CHECK_EQUAL(error, "Invalid parameter -unregistered");
 
     // Make sure registered parameters prefixed with a chain type trigger errors.
     // (Previously, they were accepted and ignored.)
     argv[1] = "-test.registered";
-    BOOST_CHECK(!test.ParseParameters(2, (char**)argv, error));
+    BOOST_CHECK(!test.ParseParameters(2, argv, error));
     BOOST_CHECK_EQUAL(error, "Invalid parameter -test.registered");
 }
 
@@ -269,7 +269,7 @@ static void TestParse(const std::string& str, bool expected_bool, int64_t expect
     std::string arg = "-value=" + str;
     const char* argv[] = {"ignored", arg.c_str()};
     std::string error;
-    BOOST_CHECK(test.ParseParameters(2, (char**)argv, error));
+    BOOST_CHECK(test.ParseParameters(2, argv, error));
     BOOST_CHECK_EQUAL(test.GetBoolArg("-value", false), expected_bool);
     BOOST_CHECK_EQUAL(test.GetBoolArg("-value", true), expected_bool);
     BOOST_CHECK_EQUAL(test.GetIntArg("-value", 99998), expected_int);
@@ -331,7 +331,7 @@ BOOST_AUTO_TEST_CASE(util_GetBoolArg)
     std::string error;
     LOCK(testArgs.cs_args);
     testArgs.SetupArgs({a, b, c, d, e, f});
-    BOOST_CHECK(testArgs.ParseParameters(7, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(7, argv_test, error));
 
     // Each letter should be set.
     for (const char opt : "abcdef")
@@ -368,7 +368,7 @@ BOOST_AUTO_TEST_CASE(util_GetBoolArgEdgeCases)
     const char *argv_test[] = {"ignored", "-nofoo", "-foo", "-nobar=0"};
     testArgs.SetupArgs({foo, bar});
     std::string error;
-    BOOST_CHECK(testArgs.ParseParameters(4, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(4, argv_test, error));
 
     // This was passed twice, second one overrides the negative setting.
     BOOST_CHECK(!testArgs.IsArgNegated("-foo"));
@@ -380,7 +380,7 @@ BOOST_AUTO_TEST_CASE(util_GetBoolArgEdgeCases)
 
     // Config test
     const char *conf_test = "nofoo=1\nfoo=1\nnobar=0\n";
-    BOOST_CHECK(testArgs.ParseParameters(1, (char**)argv_test, error));
+    BOOST_CHECK(testArgs.ParseParameters(1, argv_test, error));
     testArgs.ReadConfigString(conf_test);
 
     // This was passed twice, second one overrides the negative setting,
@@ -395,7 +395,7 @@ BOOST_AUTO_TEST_CASE(util_GetBoolArgEdgeCases)
     // Combined test
     const char *combo_test_args[] = {"ignored", "-nofoo", "-bar"};
     const char *combo_test_conf = "foo=1\nnobar=1\n";
-    BOOST_CHECK(testArgs.ParseParameters(3, (char**)combo_test_args, error));
+    BOOST_CHECK(testArgs.ParseParameters(3, combo_test_args, error));
     testArgs.ReadConfigString(combo_test_conf);
 
     // Command line overrides, but doesn't erase old setting
@@ -655,38 +655,38 @@ BOOST_AUTO_TEST_CASE(util_GetChainTypeString)
     const char* testnetconf = "testnet=1\nregtest=0\n[test]\nregtest=1";
     std::string error;
 
-    BOOST_CHECK(test_args.ParseParameters(0, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(0, argv_testnet, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "main");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_testnet, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_regtest, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_regtest, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "regtest");
 
-    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_test_no_reg, error));
+    BOOST_CHECK(test_args.ParseParameters(3, argv_test_no_reg, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_both, error));
+    BOOST_CHECK(test_args.ParseParameters(3, argv_both, error));
     BOOST_CHECK_THROW(test_args.GetChainTypeString(), std::runtime_error);
 
-    BOOST_CHECK(test_args.ParseParameters(0, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(0, argv_testnet, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_testnet, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_regtest, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_regtest, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_THROW(test_args.GetChainTypeString(), std::runtime_error);
 
-    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_test_no_reg, error));
+    BOOST_CHECK(test_args.ParseParameters(3, argv_test_no_reg, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_both, error));
+    BOOST_CHECK(test_args.ParseParameters(3, argv_both, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_THROW(test_args.GetChainTypeString(), std::runtime_error);
 
@@ -694,23 +694,23 @@ BOOST_AUTO_TEST_CASE(util_GetChainTypeString)
     // [test] regtest=1 potentially relevant) doesn't break things
     test_args.SelectConfigNetwork("test");
 
-    BOOST_CHECK(test_args.ParseParameters(0, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(0, argv_testnet, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_testnet, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_testnet, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_regtest, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_regtest, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_THROW(test_args.GetChainTypeString(), std::runtime_error);
 
-    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_test_no_reg, error));
+    BOOST_CHECK(test_args.ParseParameters(2, argv_test_no_reg, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
-    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_both, error));
+    BOOST_CHECK(test_args.ParseParameters(3, argv_both, error));
     test_args.ReadConfigString(testnetconf);
     BOOST_CHECK_THROW(test_args.GetChainTypeString(), std::runtime_error);
 }
diff --git a/src/wallet/crypter.cpp b/src/wallet/crypter.cpp
index e2799c2d05..57a19fb5f2 100644
--- a/src/wallet/crypter.cpp
+++ b/src/wallet/crypter.cpp
@@ -112,7 +112,7 @@ bool EncryptSecret(const CKeyingMaterial& vMasterKey, const CKeyingMaterial &vch
     memcpy(chIV.data(), &nIV, WALLET_CRYPTO_IV_SIZE);
     if(!cKeyCrypter.SetKey(vMasterKey, chIV))
         return false;
-    return cKeyCrypter.Encrypt(*((const CKeyingMaterial*)&vchPlaintext), vchCiphertext);
+    return cKeyCrypter.Encrypt(vchPlaintext, vchCiphertext);
 }
 
 bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCiphertext, const uint256& nIV, CKeyingMaterial& vchPlaintext)