返回int指针？ [英] Returning int pointer ?
问题描述
我有以下代码片段 -
int * createIncidenceMatrix（int numEdges，int numVertices）{
int * p =（int *）calloc（ （numEdges * numVertices），sizeof（int））;
if（p == NULL）{
printf（无法分配内存）;
退出（0）;
}
返回p;
}
void createIncidencePerView（ int numEdges，int numVertices，int viewId）{
int * pnew = createIncidenceMatrix（numEdges，numVertices）;
}
这段代码编译得很好。我想知道这是否会像
那样运行。显然，我也试过运行代码。我的问题是 -
当createIncidenceMatrix（）返回p这是本地变量时，是否会在返回呼叫时取消分配？
因此，当我在
createIncidencePerView（）内部进行createIncidenceMatrix（）调用时，调用createIncidenceMatrix（）会尝试
为pnew指针分配解除分配的本地指针？
谢谢
Mahendra
" Mahendra" < im ** @ cc.gatech.eduwrote in message
news：gd ********** @ news-int2.gatech.edu ...
< blockquote class =post_quotes>
>我有以下代码片段 -
int * createIncidenceMatrix（int numEdges，int numVertices）{
int * p =（int *）calloc（（numEdges * numVertices），sizeof（int））;
if（p == NULL）{
printf（"无法分配内存）;
退出（0）;
}
返回p;
}
void createIncidencePerView（int numEdges，int numVertices，int viewId）{
int * pnew = createIncidenceMatrix（numEdges，numVertices）;
}
此代码编译良好。我想知道这是否会像
那样运行。显然，我也试过运行代码。我的问题是 -
当createIncidenceMatrix（）返回p是本地变量时，是否会在返回呼叫时取消分配？
p是一个指针（指向您已分配的内存）。它占用的几个字节
/将在返回时释放，但不会在这些字节的副本（指针变量p的
值）之前取消分配从功能返回。
-
Bartc
Bartc写道：
>
" Mahendra" < im ** @ cc.gatech.eduwrote in message
news：gd ********** @ news-int2.gatech.edu ...
< blockquote class =post_quotes>
>我有以下代码片段 -
int * createIncidenceMatrix（int numEdges，int numVertices）{
int * p =（int *） calloc（（numEdges * numVertices），sizeof（int））;
if（p == NULL）{
printf（无法分配内存）;
exit（0）;
}
返回p;
}
void createIncidencePerView（int numEdges，int numVertices，int viewId）{
int * pnew = createIncidenceMatrix（numEdges， numVertices）;
}
这段代码编译得很好。我想知道这是否会像
那样运行。显然，我也试过运行代码。我的问题是 -
当createIncidenceMatrix（）返回p这是局部变量时，是否会在返回呼叫时取消分配？
p是一个指针（指向您已分配的内存）。它需要的几个字节
up / will /将在返回时释放，但不会在这些字节的副本之前
（指针变量p的值）已经被取消分配从
函数返回。
它会复制字节 - 保存指针变量还是复制字节
持有指针变量的值？
如果按照你所描述的那样执行后者，这个内存在哪里？
分配 - 堆？这是否意味着返回 call创建堆内存副本？
谢谢
Mahendra
我得到了我正在寻找的回复来自Andrey。
谢谢所有
Mahendra
Mahendra写道：
Bartc写道：
>" Mahendra" < im ** @ cc.gatech.eduwrote in message
新闻：gd ********** @ news-int2.gatech.edu ...
>>我有以下代码片段 -
int * createIncidenceMatrix（int numEdges，int numVertices）{
int * p =（int *）calloc（ （numEdges * numVertices），sizeof（int））;
if（p == NULL）{
printf（无法分配内存）;
exit（0）;
}
返回p;
}
void createIncidencePerView（int numEdges，int numVertices，int viewId）{
int * pnew = createIncidenceMatrix（numEdges，numVertices） ;
}
这个代码编译得很好。我想知道这是否会像
那样运行。显然，我也试过运行代码。我的问题是 -
当createIncidenceMatrix（）返回p这是局部变量时，是否会在返回呼叫时取消分配？
p是一个指针（指向您已分配的内存）。它需要的几个字节在返回时将被释放/将被释放，而不是在那些字节的副本之前（指针变量p的值）已经从
返回函数。
它会复制字节 - 保存指针变量还是复制字节
持有指针变量的值？
如果你按照你所描述的那样做了后者，这个内存在哪里？
分配 - 堆？这是否意味着返回 call创建堆内存副本？
谢谢
Mahendra
I have following code snippet -
int *createIncidenceMatrix(int numEdges, int numVertices) {
int *p = (int *) calloc((numEdges*numVertices), sizeof(int));
if(p == NULL) {
printf("Could not allocate memory");
exit(0);
}
return p;
}
void createIncidencePerView(int numEdges, int numVertices, int viewId) {
int *pnew = createIncidenceMatrix(numEdges, numVertices);
}
This code compiles fine. I am trying to understand if this will run as
intended. Obviously, I tried running the code also. My question is -
When createIncidenceMatrix() return p which is local variable, will p
get deallocated at return call ?
So when i make createIncidenceMatrix() call inside
createIncidencePerView(), will the call createIncidenceMatrix() tries to
assign deallocated local pointer to the pnew pointer ?
Thanks
Mahendra
"Mahendra" <im**@cc.gatech.eduwrote in message
news:gd**********@news-int2.gatech.edu...>I have following code snippet -
int *createIncidenceMatrix(int numEdges, int numVertices) {
int *p = (int *) calloc((numEdges*numVertices), sizeof(int));
if(p == NULL) {
printf("Could not allocate memory");
exit(0);
}
return p;
}
void createIncidencePerView(int numEdges, int numVertices, int viewId) {
int *pnew = createIncidenceMatrix(numEdges, numVertices);
}
This code compiles fine. I am trying to understand if this will run as
intended. Obviously, I tried running the code also. My question is -
When createIncidenceMatrix() return p which is local variable, will p
get deallocated at return call ?p is a pointer (to the memory you''ve allocated). The few bytes it takes up
/will/ be deallocated on return, but not before a copy of those bytes (the
value of the pointer variable p) has been made to return from the function.
--
Bartc
Bartc wrote:>
"Mahendra" <im**@cc.gatech.eduwrote in message
news:gd**********@news-int2.gatech.edu...>I have following code snippet -
int *createIncidenceMatrix(int numEdges, int numVertices) {
int *p = (int *) calloc((numEdges*numVertices), sizeof(int));
if(p == NULL) {
printf("Could not allocate memory");
exit(0);
}
return p;
}
void createIncidencePerView(int numEdges, int numVertices, int viewId) {
int *pnew = createIncidenceMatrix(numEdges, numVertices);
}
This code compiles fine. I am trying to understand if this will run as
intended. Obviously, I tried running the code also. My question is -
When createIncidenceMatrix() return p which is local variable, will p
get deallocated at return call ?
p is a pointer (to the memory you''ve allocated). The few bytes it takes
up /will/ be deallocated on return, but not before a copy of those bytes
(the value of the pointer variable p) has been made to return from the
function.
Will it copy the bytes - holding pointer variable or copy the bytes
holding the value of pointer variable ?
If it does the latter as described by you, where is this memory
allocated - heap ? Does this mean "return" call creates heap memory copy ?
Thanks
Mahendra
I got the response i was looking for from Andrey.
Thanks all
Mahendra
Mahendra wrote:Bartc wrote:>"Mahendra" <im**@cc.gatech.eduwrote in message
news:gd**********@news-int2.gatech.edu...>>I have following code snippet -
int *createIncidenceMatrix(int numEdges, int numVertices) {
int *p = (int *) calloc((numEdges*numVertices), sizeof(int));
if(p == NULL) {
printf("Could not allocate memory");
exit(0);
}
return p;
}
void createIncidencePerView(int numEdges, int numVertices, int viewId) {
int *pnew = createIncidenceMatrix(numEdges, numVertices);
}
This code compiles fine. I am trying to understand if this will run as
intended. Obviously, I tried running the code also. My question is -
When createIncidenceMatrix() return p which is local variable, will p
get deallocated at return call ?p is a pointer (to the memory you''ve allocated). The few bytes it takes
up /will/ be deallocated on return, but not before a copy of those bytes
(the value of the pointer variable p) has been made to return from the
function.
Will it copy the bytes - holding pointer variable or copy the bytes
holding the value of pointer variable ?
If it does the latter as described by you, where is this memory
allocated - heap ? Does this mean "return" call creates heap memory copy ?
Thanks
Mahendra
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