c++/c中free已經free過的記憶體會出現的現象

/**********************************************************************                        測試多次free的後果***********************************************************************/#include<iostream>#include<cstdio>using namespace std;int main(){int *p = (int *)malloc(100);free(p);cout<<"已經free一次了，再free一次..."<<endl;free(p);return 0;}

其中的_CrtIsValidHeapPointer(pUserData)在MSDN中的描述是：
The _CrtIsValidHeapPointer function is used to ensure that a specific memory address is within the local heap. The “local” heap refers to the heap created and managed by a particular instance of the C run-time library. If a dynamically linked
library (DLL) contains a static link to the run-time library, then it has its own instance of the run-time heap, and therefore its own heap, independent of the application’s local heap. When_DEBUG
is not defined, calls to_CrtIsValidHeapPointer are removed during preprocessing.

 

為了防止迷途指標，或者是多次free()帶來不可預知的異常，最好是將對應的指標，置為NULL，這樣比較安全。