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When is memory allocated and de-allocated static and dynamic memory in C?


By : Test Seventyseven
Date : September 14 2020, 09:00 AM
hop of those help? There are 3 different kinds of storage duration in C language:
static: the lifetime of the variable is the lifetime of the program. It is allocated at load time (only defined at compile time) and only freed when the operation system unloads the program. Static variables are variables declared outside any functions, and local variables (declared in a function or block) having the static modifier automatic: automatic variables are declared inside a block (or function), with no storage modifier. Their lifetime starts at the beginning of the bloc and ends at the end of the bloc. They are generally allocated at the beginning of the bloc and deallocated at its end, but because of the as if rule, optimizing compilers could allocate them sooner and free them later, for example if the bloc in located inside a loop. dynamic: they are allocated manually through malloc, and will only be deallocated by free
code :


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stack allocated memory versus dynamically allocated memory


By : Kelson
Date : March 29 2020, 07:55 AM
seems to work fine I wouldn't say that any one way of allocating a structure has "more chance of corruption". Whatever is causing the corruption could happen just as easily however it's allocated.
I'd say you'd be better off fixing the source of the corruption: You can use gdb to put a breakpoint on write to the corrupted variable with watch . Alternatively, you can also put a breakpoint when you detect corruption, and then use reverse debugging to find where the corruption occurred.
code :
void foo() {
    int a[10]; // stack
    static int b[10]; // static

    int *c = malloc(sizeof(int) * 10); // dynamic on the heap
}
void foo() {
    static int a = 0;
    a++;
    printf("%d\n",a);
}
static void foo() { ... }
static int x;

free allocated memory in 2D dynamic memory allocation array in C++


By : mbox
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further You have to go through your matrix and delete each array. At the end of doing that you can delete the matrix itself
code :
// free dynamically allocated memory
for( int i = 0 ; i < *row ; i++ )
{
    delete[] matrix[i]; // delete array within matrix
}
// delete actual matrix
delete[] matrix;

dynamic memory allocation in c , free some part of memory that is allocated before using malloc()


By : ycam
Date : March 29 2020, 07:55 AM
will be helpful for those in need You should use the standard library function realloc. As the name suggests, it reallocates a block of memory. Its prototype is (contained in the header stdlib.h)
code :
 void *realloc(void *ptr, size_t size);
// allocate memory for 10 integers
int *arr = malloc(10 * sizeof *arr);
// check arr for NULL in case malloc fails

// save the value of arr in temp in case
// realloc fails
int *temp = arr;  

// realloc may keep the same block of memory
// and free the memory for the extra 5 elements
// or may allocate a new block for 5 elements,
// copy the first five elements from the older block to the
// newer block and then free the older block
arr = realloc(arr, 5 * sizeof *arr);
if(arr == NULL) {
    // realloc failed
    arr = temp;
}

How to add contiguous blocks of memory (dynamically) to a previosly allocated dynamic memory


By : Qzak
Date : March 29 2020, 07:55 AM
I wish this helpful for you Now that i am aware of std::vector i think i can use it for this problem. I haven't posted the entire code because I think it will add to too much of details that are not relevant.
code :
vector<vector<int> > grid;
dist_y = get_y();        //returns the number of blocks in Y direction
if(dist_y > threshold){
    forward();          //moves a step forward.
    dist_x = get_x();   //returns blocks available in X direction.
    vector<int> col;
    for(int i = 0; i < dist_x; i++) {
        col.push_back(1);   //1 indicates there is free space there.
    }
    grid.push_back(col);
}  

C free() function called on static memory (on not dynamically allocated memory)


By : Noviana Arifin
Date : March 29 2020, 07:55 AM
will help you It's against the rules, so just about anything might happen. free() might print an error message. The program might crash with a segmentation violation or other memory access error. The error might be silently ignored. Or the error might lead to corruption of the malloc/free heap such that an error or crash might happen during some later call to malloc or free.
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