confused：vector< char *>和malloc [英] confused: vector<char*> and malloc

问题描述

矢量< char *之> m_Text;

m_Text.resize（1）;

char * foo =" FOO";

char * bar =" BAR" ;

char * foobar =（char *）malloc（strlen（foo）+ strlen（bar）+ 1）;

if（foobar）

{

strcpy（foobar，foo）;

strcat（foobar，bar）;

}

m_Text [0] = foobar;


//当m_Text超出范围时，m_Text [0]会被释放吗？如果没有，我应该在析构函数中使用
免费调用（m_Text [0]）吗？

解决方案

Richard写道：

vector< char *> m_Text;
m_Text.resize（1）;


这使''m_Text''长1个元素。由于''m_Text''在此之前是空的

，它会向它添加1个指针并使其为空。

char * foo =" FOO";
char * bar =" BAR" ;;
char * foobar =（char *）malloc（strlen（foo）+ strlen（bar）+ 1）;
if（foobar）
{
strcpy（foobar，foo）;
strcat（foobar，bar）;
}


此时''foobar''是一个指向7个字符数组的指针，分配在
免费商店中。数组有F，O，O，O，B，A，R，\\0 '

依旧。

m_Text [0] = foobar;


这使得向量''m_Text''中唯一元素的值与指向该7字符数组的指针相同。

。

//当m_Text超出范围时，m_Text [0]会被释放吗？


No.

如果没有，我应该在析构函数中免费调用（m_Text [0]）吗？

可能。假设你在讨论

中类的析构函数，''m_Text''是数据成员。


V

Richard写道：

vector< char *> m_Text;
m_Text.resize（1）;
char * foo =" FOO";
char * bar =" BAR" ;;
char * foobar =（char * ）malloc（strlen（foo）+ strlen（bar）+ 1）;


malloc是C，为什么不使用新的？

if（foobar）
{
strcpy（foobar，foo）;
strcat（foobar，bar）;
}
m_Text [0] = foobar;

//当m_Text超出范围时，m_Text [0]会被释放？如果没有，我应该在析构函数中调用free（m_Text [0]）吗？

尝试这个，如果你不想自己管理内存


vector< string> m_Text;


char * foo =" FOO";

char * bar =" BAR";


string foobar（foo）;

foobar.append（bar）;


m_Text.push_back（foobar）;

"凯尔" <在***** @ e.mail.com>在消息中写道

news：dd ********** @ nemesis.news.tpi.pl ...

Richard写道：

vector< char *> m_Text;
m_Text.resize（1）;
char * foo =" FOO";
char * bar =" BAR" ;;
char * foobar =（char * ）malloc（strlen（foo）+ strlen（bar）+ 1）;
malloc是C，为什么不使用new？

malloc也是C ++ 。


它用于在C ++中分配原始内存。由于new（和new []）分配

空间并构造对象，new（和new []）不适合当

不足以获得信息时构建对象。

尝试这个，如果你不想自己管理内存

vector< string> m_Text;

很棒的建议！


阿里

vector<char*> m_Text;
m_Text.resize(1);
char* foo = "FOO";
char* bar = "BAR";
char* foobar = (char*)malloc(strlen(foo) + strlen(bar) + 1);
if (foobar)
{
strcpy(foobar, foo);
strcat(foobar, bar);
}
m_Text[0] = foobar;

// Will m_Text[0] get freed when m_Text goes out of scope? If not, should I
call free(m_Text[0]) in the destructor?

解决方案

Richard wrote:

vector<char*> m_Text;
m_Text.resize(1);
This makes ''m_Text'' to be 1 element long. And since ''m_Text'' was empty
prior to that, it adds 1 pointer to it and makes it null.
char* foo = "FOO";
char* bar = "BAR";
char* foobar = (char*)malloc(strlen(foo) + strlen(bar) + 1);
if (foobar)
{
strcpy(foobar, foo);
strcat(foobar, bar);
}
At this point ''foobar'' is a pointer to 7 character array, allocated in
the free store. The array has ''F'', ''O'', ''O'', ''O'', ''B'', ''A'', ''R'', ''\0''
in it, in sequence.
m_Text[0] = foobar;
This makes the value of the only element in the vector ''m_Text'' to be the
same as the pointer to that 7-character array.
// Will m_Text[0] get freed when m_Text goes out of scope?
No.
If not, should I
call free(m_Text[0]) in the destructor?

Probably. Assuming you''re talking about the destructor of the class in
which ''m_Text'' is a data member.

V

Richard wrote:

vector<char*> m_Text;
m_Text.resize(1);
char* foo = "FOO";
char* bar = "BAR";
char* foobar = (char*)malloc(strlen(foo) + strlen(bar) + 1);
malloc is C, why dont you use new ?
if (foobar)
{
strcpy(foobar, foo);
strcat(foobar, bar);
}
m_Text[0] = foobar;

// Will m_Text[0] get freed when m_Text goes out of scope? If not, should I
call free(m_Text[0]) in the destructor?

try this if you dont want to manage memory on your own

vector<string> m_Text;

char* foo = "FOO";
char* bar = "BAR";

string foobar(foo);
foobar.append( bar );

m_Text.push_back( foobar );

"Kyle" <in*****@e.mail.com> wrote in message
news:dd**********@nemesis.news.tpi.pl...

Richard wrote:

vector<char*> m_Text;
m_Text.resize(1);
char* foo = "FOO";
char* bar = "BAR";
char* foobar = (char*)malloc(strlen(foo) + strlen(bar) + 1);
malloc is C, why dont you use new ?

malloc is C++ too.

It is used to allocate raw memory in C++. Since new (and new[]) allocates
space and constructs object(s), new (and new[]) is not suitable when there
is not enough information to construct the object(s).
try this if you dont want to manage memory on your own

vector<string> m_Text;

Great advice!

Ali

这篇关于confused：vector&lt; char *&gt;和malloc的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！