CODEWITHSUNDEEP
cpointers
some_id
some_id

Reputation: 29896

Copying data in pointers

How does one copy the data that is pointed to by another pointer?

I have the following

void *startgpswatchdog(void *ptr)
{
    GPSLocation *destination;
    *destination = (GPSLocation *) ptr;

Will this do this correctly?

I free the data that is passed into thread after passing it, so I need to copy the data.

Upvotes: 6

Views: 26312

Answers (3)

yossi
yossi

Reputation: 13315

you need to allocate memory before you assign to the address pointed by the pointer. why do you need a pointer here ? why not use 

void *startgpswatchdog(void *ptr)
{
GPSLocation destination;
destination = (GPSLocation) *ptr;
}

and later if you need this variable address just use

&destination

just dont forget its a local variable :)

Upvotes: 0

user2100815
user2100815

Reputation:

You can do it if the pointer you ae copying to actually points at something:

void *startgpswatchdog(void *ptr)
{
    GPSLocation *destination = malloc( sizeof( GPSLocation ) );
    *destination = * (GPSLocation *) ptr;
}

or perhaps better:

void *startgpswatchdog(void *ptr)
{
    GPSLocation destination;
    destination = * (GPSLocation *) ptr;
}

Upvotes: 0

Mihran Hovsepyan
Mihran Hovsepyan

Reputation: 11108

If you want to copy data you should allocate new memory via malloc, then copy your memory via memcpy.

void *startgpswatchdog(void *ptr)
{
    GPSLocation *destination = malloc(sizeof(GPSLocation));
    memcpy(destination, ptr, sizeof(GPSLocation));
}

Upvotes: 12

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