struct

问题 If i have the following in a function: struct example *A=malloc(sizeof(struct example)); does the node/memory space created where A points to get destroyed after the function ends/leaves? Or does it stay in the heap? 回答1: No. memory allocated by malloc will stay allocated until free 'd. Doing things like this: char * function(void) { char c = 'a'; return &c; } on the other hand, is bad, because this object DOES go out of scope when the function ends. malloc allocates memory on the heap.

问题 If i have the following in a function: struct example *A=malloc(sizeof(struct example)); does the node/memory space created where A points to get destroyed after the function ends/leaves? Or does it stay in the heap? 回答1: No. memory allocated by malloc will stay allocated until free 'd. Doing things like this: char * function(void) { char c = 'a'; return &c; } on the other hand, is bad, because this object DOES go out of scope when the function ends. malloc allocates memory on the heap.

问题 I'm dealing with Simulink Design Verifier and want to extract some information on my own. Therefore, I want to count the number of Objectives and how much of them have been satisfied. 'Objectives' is a struct itself: Objectives<1x10 struct> Counting the number of objectives is easy: length(fieldnames(Objectives)) The content of 'Objectives' are also structs. Each such struct has the following content: type status label Now I want to count how many elements in 'Objectives' satisfy the property

问题 Isn't forward declaration, whether for structures or functions, supposed to do what forward declaration is expected to do, ie, to let us use the structure or function before they are defined? Why is the forward declaration of a structure not working in my code? And the main thing that just misses me, is forward declaration of structures of any use in C at all? When is it used? Can you please give me a small C program example to illustrate this? My program gives the error error: storage size

问题 I've been reading about SOA and I wanted to try an implement it in a system that I am building up. I am writing some simple C struct to do some tests but I am a bit confused, right now I have 3 different struct for a vec3 . I will show them below and then go into further details about the question. struct vec3 { size_t x, y, z; }; struct vec3_a { size_t pos[3]; }; struct vec3_b { size_t* x; size_t* y; size_t* z; }; struct vec3 vec3(size_t x, size_t y, size_t z) { struct vec3 v; v.x = x; v.y =

问题 I have pyspark dataframe with multiple columns (Around 30) of nested structs, that I want to write into csv. (struct In order to do it, I want to stringify all of the struct columns. I've checked several answers here: Pyspark converting an array of struct into string PySpark: DataFrame - Convert Struct to Array PySpark convert struct field inside array to string This is the structure of my dataframe (with around 30 complex keys): root |-- 1_simple_key: string (nullable = true) |-- 2_simple

问题 I'm trying to write a program, when the program is performing an operation (Example: search, update, or add), it should be direct access. The program should not read all the records sequentially to reach a record. #include <iostream> #include <fstream> #include <string> using namespace std; struct Student{ int Id; int Money; int Age; char name[15]; }; void main(){ Student buffer; ofstream BinaryFile("student", ios::binary); ifstream WorkerText("worker.txt"); //--------------------------------

问题 I'm trying to write a program, when the program is performing an operation (Example: search, update, or add), it should be direct access. The program should not read all the records sequentially to reach a record. #include <iostream> #include <fstream> #include <string> using namespace std; struct Student{ int Id; int Money; int Age; char name[15]; }; void main(){ Student buffer; ofstream BinaryFile("student", ios::binary); ifstream WorkerText("worker.txt"); //--------------------------------

问题 #include "seq.h" #include <stdio.h> #include <stdlib.h> typedef struct stack_node { ETYPE data; struct stack_node *prev, *next; }NODE; struct seq_struct { // "Container" struct NODE* top, *bottom; int size; }; /** * DESCRIPTION: adds a new element to the "back" of * the seq * * [2 4] * add_back 7 * [2 4 7] * * */ void seq_add_back(Seq seq, ETYPE val){ NODE* endq = malloc(sizeof(NODE)); endq->next =NULL; endq->prev = seq->bottom; endq->data = val; seq->bottom->next=endq; seq->bottom = endq;

问题 I'm trying to convert the following perl code: unpack(.., "Z*") to python, however the lack of a "*" format modifier in struct.unpack() seems to make this impossible. Is there a way I can do this in python? P.S. The "*" modifier in perl from the perldoc - Supplying a * for the repeat count instead of a number means to use however many items are left, ... So although python has a numeric repeat count like perl, it seems to lack a * repeat count. 回答1: python's struct.unpack doesn't have the Z