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Another frequent source of dangling pointers is a jumbled combination of malloc() and free() library calls: a pointer becomes dangling when the block of memory it points to is freed. As with the previous example one way to avoid this is to make sure to reset the pointer to null after freeing its reference—as demonstrated below.
They show the same erratic behaviour as dangling pointers, though they are less likely to stay undetected. Invalid free – passing an invalid address to free can corrupt the heap. Mismatched free – when multiple allocators are in use, attempting to free memory with a deallocation function of a different allocator [26]
The "sawtooth" pattern of memory utilization: the sudden drop in used memory is a candidate symptom for a memory leak. If the memory leak is in the kernel, the operating system itself will likely fail. Computers without sophisticated memory management, such as embedded systems, may also completely fail from a persistent memory leak.
Using non-owned memory: It is common to use pointers to access and modify memory. If such a pointer is a null pointer, dangling pointer (pointing to memory that has already been freed), or to a memory location outside of current stack or heap bounds, it is referring to memory that is not then possessed by the program. Using such pointers is a ...
Failures to adhere to this pattern, such as memory usage after a call to free (dangling pointer) or before a call to malloc (wild pointer), calling free twice ("double free"), etc., usually causes a segmentation fault and results in a crash of the program. These errors can be transient and hard to debug – for example, freed memory is usually ...
Semantic garbage cannot be automatically collected in general, and thus causes memory leaks even in garbage-collected languages. Detecting and eliminating semantic garbage is typically done using a specialized debugging tool called a heap profiler , which allows one to see which objects are live and how they are reachable, enabling one to ...
A code sanitizer is a programming tool that detects bugs in the form of undefined or suspicious behavior by a compiler inserting instrumentation code at runtime. The class of tools was first introduced by Google's AddressSanitizer (or ASan) of 2012, which uses directly mapped shadow memory to detect memory corruption such as buffer overflows or accesses to a dangling pointer (use-after-free).
This is because any pointers to objects will be invalidated if the garbage collector moves those objects (they become dangling pointers). For interoperability with native code, the garbage collector must copy the object contents to a location outside of the garbage collected region of memory.