Merge #20429: refactor: replace (sizeof(a)/sizeof(a[0])) with C++17 std::size

e829c9afbf75e930db6c3fe77a269b0af5e7a3ad refactor: replace sizeof(a)/sizeof(a[0]) by std::size (C++17) (Sebastian Falbesoner)
365539c84691d470b44d35df374d8c049f8c1192 refactor: init vectors via std::{begin,end} to avoid pointer arithmetic (Sebastian Falbesoner)
63d4ee1968144cc3d115f92baef95785abf813ac refactor: iterate arrays via C++11 range-based for loops if idx is not needed (Sebastian Falbesoner)

Pull request description:

  This refactoring PR picks up the idea of #19626 and replaces all occurences of `sizeof(x)/sizeof(x[0])` (or `sizeof(x)/sizeof(*x)`, respectively) with the now-available C++17 [`std::size`](https://en.cppreference.com/w/cpp/iterator/size)  (as [suggested by sipa](https://github.com/bitcoin/bitcoin/pull/19626#issuecomment-666487228)), making the macro `ARRAYLEN` obsolete.

  As preparation for this, two other changes are done to eliminate `sizeof(x)/sizeof(x[0])` usage:
  * all places where arrays are iterated via an index are changed to use C++11 range-based for loops If the index' only purpose is to access the array element (as [suggested by MarcoFalke](https://github.com/bitcoin/bitcoin/pull/19626#discussion_r463404541)).
  * `std::vector` initializations are done via `std::begin` and `std::end` rather than using pointer arithmetic to calculate the end (also [suggested by MarcoFalke](https://github.com/bitcoin/bitcoin/pull/20429#discussion_r567418821)).

ACKs for top commit:
  practicalswift:
    cr ACK e829c9afbf75e930db6c3fe77a269b0af5e7a3ad: patch looks correct
  fanquake:
    ACK e829c9afbf75e930db6c3fe77a269b0af5e7a3ad
  MarcoFalke:
    review ACK e829c9afbf75e930db6c3fe77a269b0af5e7a3ad 🌩

Tree-SHA512: b01d32c04b9e04d562b7717cae00a651ec9a718645047a90761be6959e0cc2adbd67494e058fe894641076711bb09c3b47a047d0275c736f0b2218e1ce0d193d

15 files changed, 41 insertions, 51 deletions

diff --git a/src/base58.cpp b/src/base58.cpp
index 65e373283c..fb04673c5c 100644
--- a/src/base58.cpp
+++ b/src/base58.cpp
@@ -52,7 +52,7 @@ static const int8_t mapBase58[256] = {
     int size = strlen(psz) * 733 /1000 + 1; // log(58) / log(256), rounded up.
     std::vector<unsigned char> b256(size);
     // Process the characters.
-    static_assert(sizeof(mapBase58)/sizeof(mapBase58[0]) == 256, "mapBase58.size() should be 256"); // guarantee not out of range
+    static_assert(std::size(mapBase58) == 256, "mapBase58.size() should be 256"); // guarantee not out of range
     while (*psz && !IsSpace(*psz)) {
         // Decode base58 character
         int carry = mapBase58[(uint8_t)*psz];
diff --git a/src/bench/data.cpp b/src/bench/data.cpp
index 0ae4c7cad4..481e372105 100644
--- a/src/bench/data.cpp
+++ b/src/bench/data.cpp
@@ -8,7 +8,7 @@ namespace benchmark {
 namespace data {
 
 #include <bench/data/block413567.raw.h>
-const std::vector<uint8_t> block413567{block413567_raw, block413567_raw + sizeof(block413567_raw) / sizeof(block413567_raw[0])};
+const std::vector<uint8_t> block413567{std::begin(block413567_raw), std::end(block413567_raw)};
 
 } // namespace data
 } // namespace benchmark
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 97280c0d16..4796045730 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -9,7 +9,6 @@
 #include <consensus/merkle.h>
 #include <hash.h> // for signet block challenge hash
 #include <util/system.h>
-#include <util/strencodings.h>
 #include <versionbitsinfo.h>
 
 #include <assert.h>
@@ -135,7 +134,7 @@ public:
 
         bech32_hrp = "bc";
 
-        vFixedSeeds = std::vector<SeedSpec6>(pnSeed6_main, pnSeed6_main + ARRAYLEN(pnSeed6_main));
+        vFixedSeeds = std::vector<SeedSpec6>(std::begin(pnSeed6_main), std::end(pnSeed6_main));
 
         fDefaultConsistencyChecks = false;
         fRequireStandard = true;
@@ -240,7 +239,7 @@ public:
 
         bech32_hrp = "tb";
 
-        vFixedSeeds = std::vector<SeedSpec6>(pnSeed6_test, pnSeed6_test + ARRAYLEN(pnSeed6_test));
+        vFixedSeeds = std::vector<SeedSpec6>(std::begin(pnSeed6_test), std::end(pnSeed6_test));
 
         fDefaultConsistencyChecks = false;
         fRequireStandard = false;
diff --git a/src/protocol.cpp b/src/protocol.cpp
index 56e738eaa8..0b893b9272 100644
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -5,7 +5,6 @@
 
 #include <protocol.h>
 
-#include <util/strencodings.h>
 #include <util/system.h>
 
 static std::atomic<bool> g_initial_block_download_completed(false);
@@ -86,7 +85,7 @@ const static std::string allNetMessageTypes[] = {
     NetMsgType::CFCHECKPT,
     NetMsgType::WTXIDRELAY,
 };
-const static std::vector<std::string> allNetMessageTypesVec(allNetMessageTypes, allNetMessageTypes+ARRAYLEN(allNetMessageTypes));
+const static std::vector<std::string> allNetMessageTypesVec(std::begin(allNetMessageTypes), std::end(allNetMessageTypes));
 
 CMessageHeader::CMessageHeader()
 {
diff --git a/src/qt/networkstyle.cpp b/src/qt/networkstyle.cpp
index b1081f6aee..ee70c1bc30 100644
--- a/src/qt/networkstyle.cpp
+++ b/src/qt/networkstyle.cpp
@@ -22,7 +22,6 @@ static const struct {
     {"signet", QAPP_APP_NAME_SIGNET, 35, 15},
     {"regtest", QAPP_APP_NAME_REGTEST, 160, 30},
 };
-static const unsigned network_styles_count = sizeof(network_styles)/sizeof(*network_styles);
 
 // titleAddText needs to be const char* for tr()
 NetworkStyle::NetworkStyle(const QString &_appName, const int iconColorHueShift, const int iconColorSaturationReduction, const char *_titleAddText):
@@ -81,14 +80,12 @@ NetworkStyle::NetworkStyle(const QString &_appName, const int iconColorHueShift,
 const NetworkStyle* NetworkStyle::instantiate(const std::string& networkId)
 {
     std::string titleAddText = networkId == CBaseChainParams::MAIN ? "" : strprintf("[%s]", networkId);
-    for (unsigned x=0; x<network_styles_count; ++x)
-    {
-        if (networkId == network_styles[x].networkId)
-        {
+    for (const auto& network_style : network_styles) {
+        if (networkId == network_style.networkId) {
             return new NetworkStyle(
-                    network_styles[x].appName,
-                    network_styles[x].iconColorHueShift,
-                    network_styles[x].iconColorSaturationReduction,
+                    network_style.appName,
+                    network_style.iconColorHueShift,
+                    network_style.iconColorSaturationReduction,
                     titleAddText.c_str());
         }
     }
diff --git a/src/qt/platformstyle.cpp b/src/qt/platformstyle.cpp
index c6b80fd340..aab8d8e4af 100644
--- a/src/qt/platformstyle.cpp
+++ b/src/qt/platformstyle.cpp
@@ -23,7 +23,6 @@ static const struct {
     /* Other: linux, unix, ... */
     {"other", true, true, false}
 };
-static const unsigned platform_styles_count = sizeof(platform_styles)/sizeof(*platform_styles);
 
 namespace {
 /* Local functions for colorizing single-color images */
@@ -121,15 +120,13 @@ QIcon PlatformStyle::TextColorIcon(const QIcon& icon) const
 
 const PlatformStyle *PlatformStyle::instantiate(const QString &platformId)
 {
-    for (unsigned x=0; x<platform_styles_count; ++x)
-    {
-        if (platformId == platform_styles[x].platformId)
-        {
+    for (const auto& platform_style : platform_styles) {
+        if (platformId == platform_style.platformId) {
             return new PlatformStyle(
-                    platform_styles[x].platformId,
-                    platform_styles[x].imagesOnButtons,
-                    platform_styles[x].colorizeIcons,
-                    platform_styles[x].useExtraSpacing);
+                    platform_style.platformId,
+                    platform_style.imagesOnButtons,
+                    platform_style.colorizeIcons,
+                    platform_style.useExtraSpacing);
         }
     }
     return nullptr;
diff --git a/src/random.cpp b/src/random.cpp
index af9504e0ce..9900825abb 100644
--- a/src/random.cpp
+++ b/src/random.cpp
@@ -38,7 +38,6 @@
 #include <sys/random.h>
 #endif
 #ifdef HAVE_SYSCTL_ARND
-#include <util/strencodings.h> // for ARRAYLEN
 #include <sys/sysctl.h>
 #endif
 
@@ -333,7 +332,7 @@ void GetOSRand(unsigned char *ent32)
     int have = 0;
     do {
         size_t len = NUM_OS_RANDOM_BYTES - have;
-        if (sysctl(name, ARRAYLEN(name), ent32 + have, &len, nullptr, 0) != 0) {
+        if (sysctl(name, std::size(name), ent32 + have, &len, nullptr, 0) != 0) {
             RandFailure();
         }
         have += len;
diff --git a/src/rest.cpp b/src/rest.cpp
index f872f6e59d..71426a4dc4 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -19,7 +19,6 @@
 #include <txmempool.h>
 #include <util/check.h>
 #include <util/ref.h>
-#include <util/strencodings.h>
 #include <validation.h>
 #include <version.h>
 
@@ -117,9 +116,10 @@ static RetFormat ParseDataFormat(std::string& param, const std::string& strReq)
     param = strReq.substr(0, pos);
     const std::string suff(strReq, pos + 1);
 
-    for (unsigned int i = 0; i < ARRAYLEN(rf_names); i++)
-        if (suff == rf_names[i].name)
-            return rf_names[i].rf;
+    for (const auto& rf_name : rf_names) {
+        if (suff == rf_name.name)
+            return rf_name.rf;
+    }
 
     /* If no suffix is found, return original string.  */
     param = strReq;
@@ -129,12 +129,13 @@ static RetFormat ParseDataFormat(std::string& param, const std::string& strReq)
 static std::string AvailableDataFormatsString()
 {
     std::string formats;
-    for (unsigned int i = 0; i < ARRAYLEN(rf_names); i++)
-        if (strlen(rf_names[i].name) > 0) {
+    for (const auto& rf_name : rf_names) {
+        if (strlen(rf_name.name) > 0) {
             formats.append(".");
-            formats.append(rf_names[i].name);
+            formats.append(rf_name.name);
             formats.append(", ");
         }
+    }
 
     if (formats.length() > 0)
         return formats.substr(0, formats.length() - 2);
@@ -695,6 +696,7 @@ void InterruptREST()
 
 void StopREST()
 {
-    for (unsigned int i = 0; i < ARRAYLEN(uri_prefixes); i++)
-        UnregisterHTTPHandler(uri_prefixes[i].prefix, false);
+    for (const auto& up : uri_prefixes) {
+        UnregisterHTTPHandler(up.prefix, false);
+    }
 }
diff --git a/src/test/base32_tests.cpp b/src/test/base32_tests.cpp
index 3f7c5e99ee..3b44564ddb 100644
--- a/src/test/base32_tests.cpp
+++ b/src/test/base32_tests.cpp
@@ -17,7 +17,7 @@ BOOST_AUTO_TEST_CASE(base32_testvectors)
     static const std::string vstrIn[]  = {"","f","fo","foo","foob","fooba","foobar"};
     static const std::string vstrOut[] = {"","my======","mzxq====","mzxw6===","mzxw6yq=","mzxw6ytb","mzxw6ytboi======"};
     static const std::string vstrOutNoPadding[] = {"","my","mzxq","mzxw6","mzxw6yq","mzxw6ytb","mzxw6ytboi"};
-    for (unsigned int i=0; i<sizeof(vstrIn)/sizeof(vstrIn[0]); i++)
+    for (unsigned int i=0; i<std::size(vstrIn); i++)
     {
         std::string strEnc = EncodeBase32(vstrIn[i]);
         BOOST_CHECK_EQUAL(strEnc, vstrOut[i]);
diff --git a/src/test/base64_tests.cpp b/src/test/base64_tests.cpp
index bb8d102bd0..714fccffaa 100644
--- a/src/test/base64_tests.cpp
+++ b/src/test/base64_tests.cpp
@@ -16,7 +16,7 @@ BOOST_AUTO_TEST_CASE(base64_testvectors)
 {
     static const std::string vstrIn[]  = {"","f","fo","foo","foob","fooba","foobar"};
     static const std::string vstrOut[] = {"","Zg==","Zm8=","Zm9v","Zm9vYg==","Zm9vYmE=","Zm9vYmFy"};
-    for (unsigned int i=0; i<sizeof(vstrIn)/sizeof(vstrIn[0]); i++)
+    for (unsigned int i=0; i<std::size(vstrIn); i++)
     {
         std::string strEnc = EncodeBase64(vstrIn[i]);
         BOOST_CHECK_EQUAL(strEnc, vstrOut[i]);
diff --git a/src/test/hash_tests.cpp b/src/test/hash_tests.cpp
index 87f6470afa..41a626c0ea 100644
--- a/src/test/hash_tests.cpp
+++ b/src/test/hash_tests.cpp
@@ -107,14 +107,14 @@ BOOST_AUTO_TEST_CASE(siphash)
 
     // Check test vectors from spec, one byte at a time
     CSipHasher hasher2(0x0706050403020100ULL, 0x0F0E0D0C0B0A0908ULL);
-    for (uint8_t x=0; x<ARRAYLEN(siphash_4_2_testvec); ++x)
+    for (uint8_t x=0; x<std::size(siphash_4_2_testvec); ++x)
     {
         BOOST_CHECK_EQUAL(hasher2.Finalize(), siphash_4_2_testvec[x]);
         hasher2.Write(&x, 1);
     }
     // Check test vectors from spec, eight bytes at a time
     CSipHasher hasher3(0x0706050403020100ULL, 0x0F0E0D0C0B0A0908ULL);
-    for (uint8_t x=0; x<ARRAYLEN(siphash_4_2_testvec); x+=8)
+    for (uint8_t x=0; x<std::size(siphash_4_2_testvec); x+=8)
     {
         BOOST_CHECK_EQUAL(hasher3.Finalize(), siphash_4_2_testvec[x]);
         hasher3.Write(uint64_t(x)|(uint64_t(x+1)<<8)|(uint64_t(x+2)<<16)|(uint64_t(x+3)<<24)|
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index 9c06283a58..9073a5050c 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -219,11 +219,10 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
 
     // We can't make transactions until we have inputs
     // Therefore, load 110 blocks :)
-    static_assert(sizeof(blockinfo) / sizeof(*blockinfo) == 110, "Should have 110 blocks to import");
+    static_assert(std::size(blockinfo) == 110, "Should have 110 blocks to import");
     int baseheight = 0;
     std::vector<CTransactionRef> txFirst;
-    for (unsigned int i = 0; i < sizeof(blockinfo)/sizeof(*blockinfo); ++i)
-    {
+    for (const auto& bi : blockinfo) {
         CBlock *pblock = &pblocktemplate->block; // pointer for convenience
         {
             LOCK(cs_main);
@@ -232,7 +231,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
             CMutableTransaction txCoinbase(*pblock->vtx[0]);
             txCoinbase.nVersion = 1;
             txCoinbase.vin[0].scriptSig = CScript();
-            txCoinbase.vin[0].scriptSig.push_back(blockinfo[i].extranonce);
+            txCoinbase.vin[0].scriptSig.push_back(bi.extranonce);
             txCoinbase.vin[0].scriptSig.push_back(::ChainActive().Height());
             txCoinbase.vout.resize(1); // Ignore the (optional) segwit commitment added by CreateNewBlock (as the hardcoded nonces don't account for this)
             txCoinbase.vout[0].scriptPubKey = CScript();
@@ -242,7 +241,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
             if (txFirst.size() < 4)
                 txFirst.push_back(pblock->vtx[0]);
             pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
-            pblock->nNonce = blockinfo[i].nonce;
+            pblock->nNonce = bi.nonce;
         }
         std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(*pblock);
         BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(chainparams, shared_pblock, true, nullptr));
diff --git a/src/test/scriptnum_tests.cpp b/src/test/scriptnum_tests.cpp
index 281018be9f..746d4d3c6b 100644
--- a/src/test/scriptnum_tests.cpp
+++ b/src/test/scriptnum_tests.cpp
@@ -164,9 +164,9 @@ static void RunOperators(const int64_t& num1, const int64_t& num2)
 
 BOOST_AUTO_TEST_CASE(creation)
 {
-    for(size_t i = 0; i < sizeof(values) / sizeof(values[0]); ++i)
+    for(size_t i = 0; i < std::size(values); ++i)
     {
-        for(size_t j = 0; j < sizeof(offsets) / sizeof(offsets[0]); ++j)
+        for(size_t j = 0; j < std::size(offsets); ++j)
         {
             RunCreate(values[i]);
             RunCreate(values[i] + offsets[j]);
@@ -177,9 +177,9 @@ BOOST_AUTO_TEST_CASE(creation)
 
 BOOST_AUTO_TEST_CASE(operators)
 {
-    for(size_t i = 0; i < sizeof(values) / sizeof(values[0]); ++i)
+    for(size_t i = 0; i < std::size(values); ++i)
     {
-        for(size_t j = 0; j < sizeof(offsets) / sizeof(offsets[0]); ++j)
+        for(size_t j = 0; j < std::size(offsets); ++j)
         {
             RunOperators(values[i], values[i]);
             RunOperators(values[i], -values[i]);
diff --git a/src/test/sighash_tests.cpp b/src/test/sighash_tests.cpp
index bc862de78a..2eb980e8cd 100644
--- a/src/test/sighash_tests.cpp
+++ b/src/test/sighash_tests.cpp
@@ -88,7 +88,7 @@ void static RandomScript(CScript &script) {
     script = CScript();
     int ops = (InsecureRandRange(10));
     for (int i=0; i<ops; i++)
-        script << oplist[InsecureRandRange(sizeof(oplist)/sizeof(oplist[0]))];
+        script << oplist[InsecureRandRange(std::size(oplist))];
 }
 
 void static RandomTransaction(CMutableTransaction &tx, bool fSingle) {
diff --git a/src/util/strencodings.h b/src/util/strencodings.h
index b4a61202ef..98379e9138 100644
--- a/src/util/strencodings.h
+++ b/src/util/strencodings.h
@@ -17,8 +17,6 @@
 #include <string>
 #include <vector>
 
-#define ARRAYLEN(array)     (sizeof(array)/sizeof((array)[0]))
-
 /** Used by SanitizeString() */
 enum SafeChars
 {