在本文中,如果在C++中使用new分配内存失败,那么应该如何处理呢?当使用new运算符动态创建类的对象时,该对象将占用堆中的内存。以下是必须牢记的主要内容:
- 如果堆内存中没有足够的内存怎么办?应该如何处理呢?
- 如果未分配内存,那么如何避免项目崩溃?
下面是占用大量内存的程序,因此会出现此问题。在try and catch块中使用内存分配语句,以防止内存崩溃并在内存分配失败时引发异常。
程序1:
C++
// C++ program to illustarate memory
// failure when very large memory
// is allocated
#include
using namespace std;
// Driver Code
int main()
{
// Allocate huge amount of memory
long MEMORY_SIZE = 0x7fffffff;
// Put memory allocation statement
// in the try catch block
try {
char* ptr = new char[MEMORY_SIZE];
// When memory allocation fails,
// below line is not be executed
// & control will go in catch block
cout << "Memory is allocated"
<< " Successfully" << endl;
}
// Catch Block handle error
catch (const bad_alloc& e) {
cout << "Memory Allocation"
<< " is failed: "
<< e.what()
<< endl;
}
return 0;
}
C++
// C++ program to handle memory failure
// when very large memory is allocated
#include
using namespace std;
// Drive Code
int main()
{
// Allocate huge amount of memory
long MEMORY_SIZE = 0x7fffffff;
// Allocate memory dynamically
// using "new" with "nothrow"
// version of new
char* addr = new (std::nothrow) char[MEMORY_SIZE];
// Check if addr is having
// proper address or not
if (addr) {
cout << "Memory is allocated"
<< " Successfully" << endl;
}
else {
// This part will be executed if
// large memory is allocated and
// failure occurs
cout << "Memory allocation"
<< " fails" << endl;
}
return 0;
}
输出:
Memory Allocation is failed: std::bad_alloc
无需使用try-catch块,即可解决上述内存故障问题。可以使用new运算符的nothrow版本进行修复:
- nothrow常量值用作运算符new和运算符 new []的参数,以指示这些函数在失败时不会引发异常,而是返回空指针。
- 默认情况下,当使用new运算符尝试分配内存而处理函数无法这样做时,将引发bad_alloc异常。
- 但是当nothrow用作new的参数时,它将返回一个空指针。
- 该常数(nothrow)只是nothrow_t类型的值,其唯一目的是触发采用此类型参数的函数运算符 new(或运算符 new [])的重载版本。
下面是使用nothrow运算符实现的内存分配:
程式2:
C++
// C++ program to handle memory failure
// when very large memory is allocated
#include
using namespace std;
// Drive Code
int main()
{
// Allocate huge amount of memory
long MEMORY_SIZE = 0x7fffffff;
// Allocate memory dynamically
// using "new" with "nothrow"
// version of new
char* addr = new (std::nothrow) char[MEMORY_SIZE];
// Check if addr is having
// proper address or not
if (addr) {
cout << "Memory is allocated"
<< " Successfully" << endl;
}
else {
// This part will be executed if
// large memory is allocated and
// failure occurs
cout << "Memory allocation"
<< " fails" << endl;
}
return 0;
}
输出:
Memory allocation fails
要从最佳影片策划和实践问题去学习,检查了C++基础课程为基础,以先进的C++和C++ STL课程基础加上STL。要完成从学习语言到DS Algo等的更多准备工作,请参阅“完整面试准备课程” 。