C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
来源:互联网 发布:长征5号发射失败知乎 编辑:程序博客网 时间:2024/05/20 18:50
Gotcha #63: Confusing Scope and Activation of Member new and delete
Gotcha条款63:Member New和Member Delete之生存期与活动空间的迷惑
当一个类别的对象被创建和销毁时,其所声明的member operator new和member operator delete会被唤起。施行分配的表达式所处的实际生存空间(scope)与此无关:
class String {
public:
void *operator new( size_t ); // member operator new
void operator delete( void * ); // member operator delete
void *operator new[]( size_t ); // member operator new[]
void operator delete [] ( void * ); // member operator delete[]
String( const char * = "" );
// . . .
};
void f() {
String *sp = new String( "Heap" ); // 使用 String::operator new
int *ip = new int( 12 ); // 使用 ::operator new
delete ip; // 使用 :: operator delete
delete sp; // 使用 String::delete
}
分配操作所处的生存空间无关大局,只有被分配对象的型别才真正决定哪一个分配函数被调用:
String::String( const char *s )
: s_( strcpy( new char[strlen(s)+1], s ) )
{}
字符数组在class String的scope内被分配内存,但分配使用的是global array new,而非String的那个array new——因为型别不同,char并不是String。经由显式的限定(explicit qualification),我们可以这样做:
String::String( const char *s )
: s_( strcpy( reinterpret_cast
(String::operator new[](strlen(s)+1 )),s ) )
{}
如果我们能够使用形如String::new char[strlen(s)+1]的语句来调用String的operator new[]就好了,但这是非法的,行不通。(尽管我们可以使用::new的形式来调用global operator new和global operator new[],使用::delete的形式来调用global operator delete和global operator delte[]。)
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- C++ Gotchas 条款62:替换Global New和Global Delete
- cannot add new member的解决方法
- 《Effective C++》学习笔记条款23 宁以non-member、non-friend替换member函数
- Effective C++——》条款23:宁以non-member、non-frined替换member函数
- Effective C++:条款23:宁以non-member、non-friend替换member函数
- Kingofark关于学习C++和编程的50个观点2003修订版
- C++ Gotchas 条款62:替换Global New和Global Delete
- kingofark's Ineffective C/C++:低手自序
- [转] 用php实现gb2312和unicode(UTF-8)间的编码转换
- kingofark's Ineffective C/C++:自白1:返回值的运用
- C++ Gotchas 条款63:Member New和Member Delete之生存期与活动空间的迷惑
- [转]PHP 5 数据对象 (PDO) 抽象层与 Oracle
- PHP中的代码安全和SQL Injection防范
- C++ Gotchas 条款64:抛出String Literals
- kingofark's Ineffective C/C++:自白2:有符号、无符号还有位运算,我的天!
- PHP5中数据库抽象层: PDO
- PHP中多张图片上传并校验的实现
- C++ Gotchas 条款61:检查内存分配失败的情形
- [转] 详谈 vsftpd 的设置