c++ - DEBUG_NEW 和 __FILE__ 有什么用？

Question

我看到了下面的宏，

#ifdef _DEBUG
#define new DEBUG_NEW
#UNDEF THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

上述宏的用法是什么？

谢谢

Answer 1

DEBUG_NEW 只是一个 MACRO，通常定义为:

#define DEBUG_NEW new(__FILE__, __LINE__)
#define new DEBUG_NEW

因此，无论您在哪里使用 new，它都可以跟踪文件和行号，这些文件和行号可用于定位程序中的内存泄漏。

而__FILE__、__LINE__都是predefined macros在您使用它们的地方分别评估文件名和行号!

阅读下面的文章，它非常漂亮地解释了将 DEBUG_NEW 与其他有趣的宏一起使用的技术:

A Cross-Platform Memory Leak Detector

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来自 Wikpedia ,

Debug_new refers to a technique in C++ to overload and/or redefine operator new and operator delete in order to intercept the memory allocation and deallocation calls, and thus debug a program for memory usage. It often involves defining a macro named DEBUG_NEW, and makes new become something like new(_FILE_, _LINE_) to record the file/line information on allocation. Microsoft Visual C++ uses this technique in its Microsoft Foundation Classes. There are some ways to extend this method to avoid using macro redefinition while still able to display the file/line information on some platforms. There are many inherent limitations to this method. It applies only to C++, and cannot catch memory leaks by C functions like malloc. However, it can be very simple to use and also very fast, when compared to some more complete memory debugger solutions.