Fold leaks that are referenced by other leaks
Find leaks that have no references at all, or are only referenced by
other leaks in the same strongly connected component, and hide all
referenced leaks.
Bug: 27208635
Change-Id: Ifbfd14e24e2ba0f8af7c1b887e57f34362720f2d
diff --git a/libmemunreachable/LeakFolding.cpp b/libmemunreachable/LeakFolding.cpp
new file mode 100644
index 0000000..0b4e7dd
--- /dev/null
+++ b/libmemunreachable/LeakFolding.cpp
@@ -0,0 +1,143 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <inttypes.h>
+
+#include "Allocator.h"
+#include "HeapWalker.h"
+#include "LeakFolding.h"
+#include "Tarjan.h"
+#include "log.h"
+
+// Converts possibly cyclic graph of leaks to a DAG by combining
+// strongly-connected components into a object, stored in the scc pointer
+// of each node in the component.
+void LeakFolding::ComputeDAG() {
+ SCCList<LeakInfo> scc_list{allocator_};
+ Tarjan(leak_graph_, scc_list);
+
+ Allocator<SCCInfo> scc_allocator = allocator_;
+
+ for (auto& scc_nodes: scc_list) {
+ Allocator<SCCInfo>::unique_ptr leak_scc;
+ leak_scc = scc_allocator.make_unique(scc_allocator);
+
+ for (auto& node: scc_nodes) {
+ node->ptr->scc = leak_scc.get();
+ leak_scc->count++;
+ leak_scc->size += node->ptr->range.size();
+ }
+
+ leak_scc_.emplace_back(std::move(leak_scc));
+ }
+
+ for (auto& it : leak_map_) {
+ LeakInfo& leak = it.second;
+ for (auto& ref: leak.node.references_out) {
+ if (leak.scc != ref->ptr->scc) {
+ leak.scc->node.Edge(&ref->ptr->scc->node);
+ }
+ }
+ }
+}
+
+void LeakFolding::AccumulateLeaks(SCCInfo* dominator) {
+ std::function<void(SCCInfo*)> walk(std::allocator_arg, allocator_,
+ [&](SCCInfo* scc) {
+ if (scc->accumulator != dominator) {
+ scc->accumulator = dominator;
+ dominator->cuumulative_size += scc->size;
+ dominator->cuumulative_count += scc->count;
+ scc->node.Foreach([&](SCCInfo* ref) {
+ walk(ref);
+ });
+ }
+ });
+ walk(dominator);
+}
+
+bool LeakFolding::FoldLeaks() {
+ Allocator<LeakInfo> leak_allocator = allocator_;
+
+ // Find all leaked allocations insert them into leak_map_ and leak_graph_
+ heap_walker_.ForEachAllocation(
+ [&](const Range& range, HeapWalker::AllocationInfo& allocation) {
+ if (!allocation.referenced_from_root) {
+ auto it = leak_map_.emplace(std::piecewise_construct,
+ std::forward_as_tuple(range),
+ std::forward_as_tuple(range, allocator_));
+ LeakInfo& leak = it.first->second;
+ leak_graph_.push_back(&leak.node);
+ }
+ });
+
+ // Find references between leaked allocations and connect them in leak_graph_
+ for (auto& it : leak_map_) {
+ LeakInfo& leak = it.second;
+ heap_walker_.ForEachPtrInRange(leak.range,
+ [&](Range& ptr_range, HeapWalker::AllocationInfo* ptr_info) {
+ if (!ptr_info->referenced_from_root) {
+ LeakInfo* ptr_leak = &leak_map_.at(ptr_range);
+ leak.node.Edge(&ptr_leak->node);
+ }
+ });
+ }
+
+ // Convert the cyclic graph to a DAG by grouping strongly connected components
+ ComputeDAG();
+
+ // Compute dominators and cuumulative sizes
+ for (auto& scc : leak_scc_) {
+ if (scc->node.references_in.size() == 0) {
+ scc->dominator = true;
+ AccumulateLeaks(scc.get());
+ }
+ }
+
+ return true;
+}
+
+bool LeakFolding::Leaked(allocator::vector<LeakFolding::Leak>& leaked,
+ size_t limit, size_t* num_leaks_out, size_t* leak_bytes_out) {
+ size_t num_leaks = 0;
+ size_t leak_bytes = 0;
+ for (auto& it : leak_map_) {
+ const LeakInfo& leak = it.second;
+ num_leaks++;
+ leak_bytes += leak.range.size();
+ }
+
+ size_t n = 0;
+ for (auto& it : leak_map_) {
+ const LeakInfo& leak = it.second;
+ if (leak.scc->dominator) {
+ if (n++ < limit) {
+ leaked.emplace_back(Leak{leak.range,
+ leak.scc->cuumulative_count - 1,
+ leak.scc->cuumulative_size - leak.range.size()});
+ }
+ }
+ }
+
+ if (num_leaks_out) {
+ *num_leaks_out = num_leaks;
+ }
+ if (leak_bytes_out) {
+ *leak_bytes_out = leak_bytes;
+ }
+
+ return true;
+}