Use std::bit_cast

For coverage builds, we try to link against the `gcov` library (specific to the environment). But as macOS doesn't have this library and thus doesn't have the coverage tools to generate reports, the coverage builds on that platform were failing on linking.

We actually don't need to explicitly force this linking, as the `CodeCoverage` file already has correct detection logic (currently on lines 177-193), which is invoked when the `--coverage` flag is provided:
* AppleClang: Uses `xcrun -f llvm-cov` to set `GCOV_TOOL="llvm-cov gcov"`.
* Clang: Finds `llvm-cov` to set `GCOV_TOOL="llvm-cov gcov"`.
* GCC: Finds `gcov` to set `GCOV_TOOL="gcov"`.
The `GCOV_TOOL` is then passed to `gcovr` on line 416, so the correct tool is used for processing coverage data.

This change therefore removes the `gcov` suffix from lines 473 and 475 in the `CodeCoverage.cmake` file.

cmake/CodeCoverage.cmake

@@ -466,11 +466,6 @@ function (add_code_coverage_to_target name scope)
     target_compile_options(${name} ${scope} $<$<COMPILE_LANGUAGE:CXX>:${COVERAGE_CXX_COMPILER_FLAGS}>
                            $<$<COMPILE_LANGUAGE:C>:${COVERAGE_C_COMPILER_FLAGS}>)
 
-    target_link_libraries(
-        ${name}
-        ${scope}
-        $<$<LINK_LANGUAGE:CXX>:${COVERAGE_CXX_LINKER_FLAGS}
-        gcov>
-        $<$<LINK_LANGUAGE:C>:${COVERAGE_C_LINKER_FLAGS}
-        gcov>)
+    target_link_libraries(${name} ${scope} $<$<LINK_LANGUAGE:CXX>:${COVERAGE_CXX_LINKER_FLAGS}>
+                          $<$<LINK_LANGUAGE:C>:${COVERAGE_C_LINKER_FLAGS}>)
 endfunction () # add_code_coverage_to_target

include/xrpl/nodestore/Backend.h

@@ -76,16 +76,16 @@ public:
         If the object is not found or an error is encountered, the
         result will indicate the condition.
         @note This will be called concurrently.
-        @param key A pointer to the key data.
+        @param hash The hash of the object.
         @param pObject [out] The created object if successful.
         @return The result of the operation.
     */
     virtual Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) = 0;
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) = 0;
 
     /** Fetch a batch synchronously. */
     virtual std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) = 0;
+    fetchBatch(std::vector<uint256> const& hashes) = 0;
 
     /** Store a single object.
         Depending on the implementation this may happen immediately

src/libxrpl/nodestore/DatabaseNodeImp.cpp

@@ -29,7 +29,7 @@ DatabaseNodeImp::fetchNodeObject(uint256 const& hash, std::uint32_t, FetchReport
 
     try
     {
-        status = backend_->fetch(hash.data(), &nodeObject);
+        status = backend_->fetch(hash, &nodeObject);
     }
     catch (std::exception const& e)
     {
@@ -62,18 +62,10 @@ DatabaseNodeImp::fetchBatch(std::vector<uint256> const& hashes)
     using namespace std::chrono;
     auto const before = steady_clock::now();
 
-    std::vector<uint256 const*> batch{};
-    batch.reserve(hashes.size());
-    for (size_t i = 0; i < hashes.size(); ++i)
-    {
-        auto const& hash = hashes[i];
-        batch.push_back(&hash);
-    }
-
     // Get the node objects that match the hashes from the backend. To protect
     // against the backends returning fewer or more results than expected, the
     // container is resized to the number of hashes.
-    auto results = backend_->fetchBatch(batch).first;
+    auto results = backend_->fetchBatch(hashes).first;
     XRPL_ASSERT(
         results.size() == hashes.size() || results.empty(),
         "number of output objects either matches number of input hashes or is empty");

src/libxrpl/nodestore/DatabaseRotatingImp.cpp

@@ -101,7 +101,7 @@ DatabaseRotatingImp::fetchNodeObject(uint256 const& hash, std::uint32_t, FetchRe
         std::shared_ptr<NodeObject> nodeObject;
         try
         {
-            status = backend->fetch(hash.data(), &nodeObject);
+            status = backend->fetch(hash, &nodeObject);
         }
         catch (std::exception const& e)
         {

src/libxrpl/nodestore/backend/MemoryFactory.cpp

@@ -115,10 +115,9 @@ public:
     //--------------------------------------------------------------------------
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) override
     {
         XRPL_ASSERT(db_, "xrpl::NodeStore::MemoryBackend::fetch : non-null database");
-        uint256 const hash(uint256::fromVoid(key));
 
         std::lock_guard _(db_->mutex);
 
@@ -133,14 +132,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else

src/libxrpl/nodestore/backend/NuDBFactory.cpp

@@ -177,17 +177,17 @@ public:
     }
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pno) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pno) override
     {
         Status status;
         pno->reset();
         nudb::error_code ec;
         db_.fetch(
-            key,
-            [key, pno, &status](void const* data, std::size_t size) {
+            hash.data(),
+            [hash, pno, &status](void const* data, std::size_t size) {
                 nudb::detail::buffer bf;
                 auto const result = nodeobject_decompress(data, size, bf);
-                DecodedBlob decoded(key, result.first, result.second);
+                DecodedBlob decoded(hash.data(), result.first, result.second);
                 if (!decoded.wasOk())
                 {
                     status = dataCorrupt;
@@ -205,14 +205,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else

src/libxrpl/nodestore/backend/NullFactory.cpp

@@ -36,13 +36,13 @@ public:
     }
 
     Status
-    fetch(void const*, std::shared_ptr<NodeObject>*) override
+    fetch(uint256 const&, std::shared_ptr<NodeObject>*) override
     {
         return notFound;
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         return {};
     }

src/libxrpl/nodestore/backend/RocksDBFactory.cpp

@@ -237,7 +237,7 @@ public:
     //--------------------------------------------------------------------------
 
     Status
-    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) override
+    fetch(uint256 const& hash, std::shared_ptr<NodeObject>* pObject) override
     {
         XRPL_ASSERT(m_db, "xrpl::NodeStore::RocksDBBackend::fetch : non-null database");
         pObject->reset();
@@ -245,7 +245,7 @@ public:
         Status status(ok);
 
         rocksdb::ReadOptions const options;
-        rocksdb::Slice const slice(static_cast<char const*>(key), m_keyBytes);
+        rocksdb::Slice const slice(std::bit_cast<char const*>(hash.data()), m_keyBytes);
 
         std::string string;
 
@@ -253,7 +253,7 @@ public:
 
         if (getStatus.ok())
         {
-            DecodedBlob decoded(key, string.data(), string.size());
+            DecodedBlob decoded(hash.data(), string.data(), string.size());
 
             if (decoded.wasOk())
             {
@@ -288,14 +288,14 @@ public:
     }
 
     std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
-    fetchBatch(std::vector<uint256 const*> const& hashes) override
+    fetchBatch(std::vector<uint256> const& hashes) override
     {
         std::vector<std::shared_ptr<NodeObject>> results;
         results.reserve(hashes.size());
         for (auto const& h : hashes)
         {
             std::shared_ptr<NodeObject> nObj;
-            Status status = fetch(h->begin(), &nObj);
+            Status status = fetch(h, &nObj);
             if (status != ok)
                 results.push_back({});
             else

src/test/nodestore/TestBase.h

@@ -137,7 +137,7 @@ public:
         {
             std::shared_ptr<NodeObject> object;
 
-            Status const status = backend.fetch(batch[i]->getHash().cbegin(), &object);
+            Status const status = backend.fetch(batch[i]->getHash(), &object);
 
             BEAST_EXPECT(status == ok);
 
@@ -157,7 +157,7 @@ public:
         {
             std::shared_ptr<NodeObject> object;
 
-            Status const status = backend.fetch(batch[i]->getHash().cbegin(), &object);
+            Status const status = backend.fetch(batch[i]->getHash(), &object);
 
             BEAST_EXPECT(status == notFound);
         }

src/test/nodestore/Timing_test.cpp

@@ -313,7 +313,7 @@ public:
                     std::shared_ptr<NodeObject> obj;
                     std::shared_ptr<NodeObject> result;
                     obj = seq1_.obj(dist_(gen_));
-                    backend_.fetch(obj->getHash().data(), &result);
+                    backend_.fetch(obj->getHash(), &result);
                     suite_.expect(result && isSame(result, obj));
                 }
                 catch (std::exception const& e)
@@ -371,9 +371,9 @@ public:
             {
                 try
                 {
-                    auto const key = seq2_.key(i);
+                    auto const hash = seq2_.key(i);
                     std::shared_ptr<NodeObject> result;
-                    backend_.fetch(key.data(), &result);
+                    backend_.fetch(hash, &result);
                     suite_.expect(!result);
                 }
                 catch (std::exception const& e)
@@ -438,9 +438,9 @@ public:
                 {
                     if (rand_(gen_) < missingNodePercent)
                     {
-                        auto const key = seq2_.key(dist_(gen_));
+                        auto const hash = seq2_.key(dist_(gen_));
                         std::shared_ptr<NodeObject> result;
-                        backend_.fetch(key.data(), &result);
+                        backend_.fetch(hash, &result);
                         suite_.expect(!result);
                     }
                     else
@@ -448,7 +448,7 @@ public:
                         std::shared_ptr<NodeObject> obj;
                         std::shared_ptr<NodeObject> result;
                         obj = seq1_.obj(dist_(gen_));
-                        backend_.fetch(obj->getHash().data(), &result);
+                        backend_.fetch(obj->getHash(), &result);
                         suite_.expect(result && isSame(result, obj));
                     }
                 }
@@ -524,8 +524,7 @@ public:
                         std::shared_ptr<NodeObject> result;
                         auto const j = older_(gen_);
                         obj = seq1_.obj(j);
-                        std::shared_ptr<NodeObject> result1;
-                        backend_.fetch(obj->getHash().data(), &result);
+                        backend_.fetch(obj->getHash(), &result);
                         suite_.expect(result != nullptr);
                         suite_.expect(isSame(result, obj));
                     }
@@ -543,7 +542,7 @@ public:
                                 std::shared_ptr<NodeObject> result;
                                 auto const j = recent_(gen_);
                                 obj = seq1_.obj(j);
-                                backend_.fetch(obj->getHash().data(), &result);
+                                backend_.fetch(obj->getHash(), &result);
                                 suite_.expect(!result || isSame(result, obj));
                                 break;
                             }