What happens to memory after free()?
Your analogy is correct. The data in memory doesn’t disappear or anything like that; the values may indeed still be there after a free(), though attempting to read from freed memory is undefined behaviour.
dynamic-memory-allocation
What is the recommended way to align memory in C++11
Unfortunately the best I have found is allocating extra space and then using the “aligned” part. So the RingBuffer new can request an extra 64 bytes and then return the first 64 byte aligned part of that. It wastes space but will give the alignment you need. You will likely need to set the memory … Read more
Assembly x86 brk() call use
others have pointed out a few things that are wrong with your code. I would like to add that you would not add 20 bits to the current breakpoint (or 20 bytes like add rbx, 20 actually does), you would simply add 5 bytes. Also, your first syscall argument will not be in rbx, it … Read more
Malloc function (dynamic memory allocation) resulting in an error when it is used globally
You can’t execute code outside of functions. The only thing you can do at global scope is declaring variables (and initialize them with compile-time constants). malloc is a function call, so that’s invalid outside a function. If you initialize a global pointer variable with malloc from your main (or any other function really), it will … Read more
dynamic allocation/deallocation of 2D & 3D arrays
You can also allocate one array and compute individual indices. This requires fewer allocator calls and results in both less fragmentation and better cache use. typedef struct { int a; int b; int* data; } Int2d; Int2d arr2d = { 2, 3 }; arr2d.data = malloc(arr2d.a * arr2d.b * sizeof *arr2d.data); Now arr2d[r][c] becomes arr2d.data[r … Read more
Simple C implementation to track memory malloc/free?
You could allocate a few extra bytes in your wrapper and put either an id (if you want to be able to couple malloc() and free()) or just the size there. Just malloc() that much more memory, store the information at the beginning of your memory block and and move the pointer you return that … Read more
dynamic allocating array of arrays in C
The m[line][column] = 12 syntax is ok (provided line and column are in range). However, you didn’t write the code you use to allocate it, so it’s hard to get whether it is wrong or right. It should be something along the lines of m = (int**)malloc(nlines * sizeof(int*)); for(i = 0; i < nlines; … Read more
Thread ” has overflowed its stack when allocating a large array using Box
As far as I can tell, it seems like that code is still trying to allocate the array on the stack first, and then move it into the box after. It works for me if I switch to Vec<f64> in place of Box<[f64]> like this: fn new_gap(gap: usize) -> usize { let ngap = ((gap … Read more
Why, or when, do you need to dynamically allocate memory in C?
You need to use dynamic memory when: You cannot determine the maximum amount of memory to use at compile time; You want to allocate a very large object; You want to build data structures (containers) without a fixed upper size; You don’t always know how much memory you will need to set aside at compile … Read more
Is a destructor called when an object goes out of scope?
Yes, automatic variables will be destroyed at the end of the enclosing code block. But keep reading. Your question title asks if a destructor will be called when the variable goes out of scope. Presumably what you meant to ask was: will Foo’s destructor be called at the end of main()? Given the code you … Read more