dynamic-memory-allocation

问题 Im stil a beginner in C programming and I need a little help writing a code for my C programming class . The prompt is: Input for this program is a two-dimensional array of floating point data located in a file named textfile94. The input array will contain 3 rows of data with each row containing 5 columns of data. I want you to use the two-subscript method of dynamic memory allocation. Use malloc to create an array that holds pointers. Each element of that array points at another array,

问题 I'm trying to dynamically allocate memory for a 2D array inside a function in C++. A question exactly like this has been asked except that it is written using malloc and dealloc, so I was wondering if you could help me convert it to use new and delete. Here is the other question: Allocate memory 2d array in function C I tried changing it to the following code, but I'm getting errors. void assign_memory_for_board(int ROWS, int COLS, int *** board) { *board = new int**[ROWS]; for (int i = 0; i

问题 My question is about array allocation in Fortran. I have a subroutine, say readParams , where I want to read some dynamically sized arrays from files. These are also used outside the subroutine. What is the best way to handle this? In F95 it seems to be impossible to allocate within the subroutine and pass the arrays, filled with values, back to the main program. But if I allocate it in the main program and use "intent(inout)" in the subroutine it also gets deallocated there. (I'm using F90

问题 I was making a program for linked list in C++. To implement the concept, I created a pointer 'start' globally, pointing to the first element of the list. After completion of the program I tried to delete all memory allocated dynamically to prevent memory leaks, by accessing successive nodes using the start and another locally declared pointer 'p'. Here, I used a pointer pointing to the same correct addresses, but this pointer was not the one used for memory allocation, but was declared

问题 I have the following code void getPariceArray(Board board, treeNode *tn, Position *dst, int **prices, int *counter, int total) { if (tn == NULL) return NULL; if (tn->position[0] == dst[0][0] && tn->position[1] == dst[0][1]) { prices = (int **)realloc(prices, sizeof(prices) *4); prices[*counter] = (int *)malloc(sizeof(int)); printf("%d", sizeof(prices)); *prices[*counter] = total; *counter = *counter + 1; } int x = tn->position[1] - '1'; int y = tn->position[0] - 'A'; int cellPrice = board[x]

问题 For example: // is type: std::istream // str type: std::string is >> str; How does this grow str to accommodate the input? It reads character by character and calls str.push_back() (or something similar)? Or does it have a mechanism for knowing the input size before reading the input? I realize that the standard most likely doesn't specify this details, but I am more interested in common implementations (e.g. gcc ). This question is a curiosity as in C you don't know beforehand how much to

问题 Reading the manual about vector::resize http://www.cplusplus.com/reference/vector/vector/resize/ It only says what happens if the size is greater or smaller, but does not say what happens if it's equal. Is it guaranteed that on equal size it will not reallocate the array and invalidate the iterators? I wanted to avoid one branch and handle only 2 cases (>= or <) instead of 3 (< or > or ==), but if resizing to same size is undefined, then i will have to check that case too. 回答1: This is

来源： https://stackoverflow.com/questions/64029219/why-does-malloc-call-mmap-and-brk-interchangeably

来源： https://stackoverflow.com/questions/63211326/why-malloc-doesnt-allocate-memory-until-i-hit-a-certain-threshold

问题 Is there any way to free some part of memory you created by using malloc(); suppose:- int *temp; temp = ( int *) malloc ( 10 * sizeof(int)); free(temp); free() will release all 20 byte of memory but suppose i only need 10 bytes. Can i free last 10 bytes. 回答1: 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 ) void *realloc(void *ptr, size_t size); The function changes the size of