Memory leak
A memory leak is the unintended retention of allocated memory that a program no longer needs, preventing that memory from being reclaimed for reuse.
Troubleshooting Java, Second Edition
A memory leak is a software defect in which allocated memory remains unreleased after it is no longer needed.
- How it is used
- Guides profiling investigations of abnormal memory consumption before slowness, heap exhaustion, or application failure.
- How deep it goes
- Explains retained references, GC symptoms, diagnostic tools, and a failing Java example, but defers exact retention analysis to heap dumps.
- Examples
- Uses an unbounded static Java list, VisualVM memory graphs, GC-log entries, and lingering session references as diagnostic examples.
- What you can do after
- Diagnose suspected leaks with VisualVM and heap-usage logs, distinguish them from insufficient memory, and identify retained references with a heap dump.
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100 C++ Mistakes and How to Avoid Them
A memory leak is a failure to release dynamically allocated storage after it is no longer accessible or needed.
- How it is used
- Diagnoses dynamic-resource mistakes in legacy C++ and guides incremental replacement with disciplined ownership.
- How deep it goes
- Explains leaks through allocation, destruction, polymorphism, and copying, then stops short of leak-detection tooling.
- Examples
- Uses malloc/free and new/delete listings, a polymorphic Shape/Square hierarchy, and Page copy and unique_ptr examples.
- What you can do after
- Diagnose/debug leaks by matching allocation with destruction and preserving ownership across inheritance, copying, assignment, and moves.
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100 Go Mistakes and How to Avoid Them
A memory leak is a failure to release memory or another managed resource after it is no longer needed.
- How it is used
- Identifies Go code that retains large backing storage or creates repeated timeout resources despite keeping only small values.
- How deep it goes
- Traces backing-storage and timeout lifetimes through code, then compares copying, clearing references, contexts, and reusable timers.
- Examples
- Uses a large slice of byte buffers, cached UUIDs extracted from logs, and an hourly timeout in a message loop.
- What you can do after
- Diagnose/debug with it by checking retained backing storage and timeout lifetimes, then choosing copies, cleared references, or reusable timers.
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.NET in Action, Second Edition
A memory leak is a condition in which memory remains allocated or unreachable despite no longer being needed by a program.
- How it is used
- Frames memory leaks as a reliability risk of explicit heap management when comparing C++ with .NET garbage collection.
- How deep it goes
- Defines a leak through unfreed allocation and a lost pointer, without developing a leak-diagnosis procedure.
- Examples
- Uses a C++ dynamically allocated integer array and its C# array counterpart.
- What you can do after
- Diagnose/debug with it by recognizing when allocated C++ array memory is not freed before its pointer is lost.
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Idiomatic Rust
A memory leak is a failure to release dynamically allocated memory after it is no longer reachable or needed.
- How it is used
- Diagnoses unreleased heap allocations and motivates automatic cleanup through C++ object lifetime management.
- How deep it goes
- Traces malloc, pointer scope, early returns, and free, then contrasts them with C++ cleanup objects.
- Examples
- Uses malloc(sizeof(int)), a failing fopen branch, free(a), shared_ptr<int>, and ifstream.
- What you can do after
- Diagnose leaks by matching every heap allocation with cleanup across all return paths.
Related concepts
- WeakMapaddressed by · WeakMap is a JavaScript collection that associates values with weakly held object keys, which do not prevent garbage collection and whose entries cannot be enumerated.
- virtual destructoraddressed by · A virtual destructor is a destructor whose dynamic dispatch ensures that destroying an object through a base-class interface invokes the derived-class destructor.
- memory errorproduces · An out-of-memory error is a runtime failure that occurs when a process or system cannot obtain enough memory for an allocation or operation.
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