[英]Memory deallocation c++
I obviously misunderstood something using delete
. 我显然误用了
delete
。 Why is this program filling up my memory? 为什么这个程序会填满我的记忆?
void f(int* x){
x = new int[42];
}
int main(){
while(true){
int* x;
f(x);
delete[] x;
}
return 0;
}
How can I free the memory I allocated in f
from inside the main
function? 如何从
main
函数内部释放在f
分配的内存?
You are not actually modifying the x
variable in the outer function. 您实际上并没有在外部函数中修改
x
变量。
To do that, you have either to rely on the returned value of f
: 为此,您必须依靠
f
的返回值:
int* f(){
return new int[42];
}
int main(){
while(true){
int* x = f();
delete[] x;
}
return 0;
}
Or to pass the variable x
by reference: 或通过引用传递变量
x
:
void f(int*& x){
x = new int[42];
}
int main(){
while(true){
int* x;
f(x);
delete[] x;
}
return 0;
}
Or to use a pointer to pointer as an argument to f
: 或者使用指向指针的指针作为
f
的参数:
void f(int** x){
*x = new int[42];
}
int main(){
while(true){
int* x;
f(&x);
delete[] x;
}
return 0;
}
And so on... 等等...
There are memory leaks in the function 函数中存在内存泄漏
void f(int* x){
x = new int[42];
}
You allocate memory but never free it. 您分配内存,但永远不会释放它。 Function parameters are local variables of the function.
函数参数是函数的局部变量。 The function deals with a copy of the original pointer.
该函数处理原始指针的副本。 Any changes of the copy do not influence on the original argument.
复制的任何更改都不会影响原始参数。
And mpreover the program has undefined behaviour because pointer x
is not initialized. 并且mpreover程序具有未定义的行为,因为指针
x
未初始化。
int main(){
while(true){
int* x;
^^^^^^
f(x);
delete[] x;
}
return 0;
}
You need to pass the original pointer by reference. 您需要通过引用传递原始指针。 So the function should be defined like
所以功能应该像
void f(int* &x){
x = new int[42];
}
and called like 叫像
f(x);
or defined like 或定义为
void f(int* *x){
*x = new int[42];
}
and called like 叫像
f( &x );
Pass the parameter by reference. 通过引用传递参数。 You're passing it by value.
您正在通过价值传递它。
So what you might want to do is consider constructing a functor/class/struct that uses RAII... 因此,您可能要考虑构建使用RAII的函子/类/结构。
By this I mean how the standard library handles a lot of allocations. 我的意思是说标准库如何处理大量分配。
struct A {
A(){/*allocate mem*/}
~A(){/*deallocate mem*/}
}
For your particular function, 对于您的特定功能,
void f(int** x);
is most likely the signature you want. 是您想要的签名。 This will allow you to modify the array through the pointer to it.
这将允许您通过指向数组的指针来修改数组。 Though... I still recommend not doing this... the reason is what about if you decide to allocate a bunch of arrays?
虽然...我仍然建议不要这样做...原因是如果您决定分配一堆数组呢? Does the main method take responsibility for deallocating memory?
主要方法是否负责分配内存?
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