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2025-04-17 19:19 本頁(yè)面
【正文】 delete instead of delete[] for C++ array deallocation, as well as using malloc() together with delete, and using new together with free(). Buffer Overruns Buffer overruns are bugs where memory outside of the allocated boundaries is overwritten, or corrupted. Buffer overruns can occur for global variables, local variables on the stack, and dynamic variables that were allocated on the heap with memory management. One nasty artifact of memory corruption is that the bug may not bee visible at the statement where the memory is overwritten. Only later, another statement in the program will access this memory location. Because the memory location has an illegal value, the program can behave incorrectly in a number of ways: the program may pute a wrong result, or, if the illegal value is in a pointer, the program will try to access protected memory and crash. If a function pointer variable is overwritten, the program will do a jump and try to execute data as program code. The key point is that there may be no strict relation between the statement causing the memory corruption and the statement triggering the visible bug. Uninitialized Memory Bugs Reading uninitialized memory can occur because C/C++ allows creation of variables without an initial value. The programmer is fully responsible to initialize all global and local variables, either through assignment statements or through the Memory Debuggers to the Rescue 35 various C++ constructors. The memory allocation function malloc() and operator new also do not initialize or zero out the allocated memory blocks. Uninitialized variables will contain unpredictable values. Memory Debuggers to the Rescue The above categories of memory access bugs created a need for adequate debugging tools. Finding bugs related to leaked, corrupted, or uninitialized memory with a conventional debugger such as GDB turned out to be unproductive. To deal with memory leaks in large software projects, many programmers came up with the same idea. They created memory management functions/operators with special instrumentation to track where a memory block was allocated, and if each block was properly deallocated at the end of the program. Since everybody had the same memory bugs in their C/C++ programs, and since everybody improvised with custom instrumentation to track down at least some of these bugs, a market for a tool called memory debugger was created. The most wellknown too
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