dynamic-allocation

问题 Is there any existing way to emulate growing array in Fortran? Like vector in C++. I was very surprised when I haven't found anything on this subject on the Internet. As a motivation example, suppose I compute some recurrence relation and I want to store all the intermediate numbers I get. My stopping criterion is the difference between adjacent results so I cannot know beforehand how much memory I should allocate for this. 回答1: I am sure it has been shown somewhere on this site before, but I

问题 What is difference between new and new[1] ? Can I use delete with new[1] ? Edit Well well well, I should've provided the background, sorry for that. I was evaluating BoundsChecker at work with VS 2010 and it complained about a memory leak when I used delete[] on new[1]. So in theory I know how the new and delete pair should be used but this particular situation confused me about the things under the hood. Any idea whats happening? 回答1: Ed and aix are right, but there is much more going on

问题 I have a Spark Streaming job running on our cluster with other jobs(Spark core jobs). I want to use Dynamic Resource Allocation for these jobs including Spark Streaming. According to below JIRA Issue, Dynamic Allocation is not supported Spark Streaming(in 1.6.1 version). But is Fixed in 2.0.0 JIRA link According to the PDF in this issue, it says there should be a configuration field called spark.streaming.dynamicAllocation.enabled=true But I dont see this configuration in the documentation.

问题 What is the good way (understand idiomatic/good practice) to dynamically create a multidimensional array in C++. For example let say I have tree integers w , h and d and I want to create an array MyEnum my_array[w][h][d] . (Of course w, h and d are not known at compile time). Is it best to use nested std::vector or use new or something ? Bonus question : Is it possible to set the dimension dynamically too ? 回答1: In general, nesting std::vector is not a great idea. It's usually a better plan

问题 Suppose we have: int** myArray = new int*[100]; for(int i = 0; i < 100; i++){ myArray[i] = new int[3]; } What is the appropriate way to deallocate this array (which method below, if either is a correct way to do so)? 1. delete[] myArray; 2. for(int i = 0; i < 100; i++){ for(int j = 0; j < 3; j++){ delete myArray[i][j]; } } delete[] myArray; Intuitively it seems like we should do something like 2. since we want all of the memory we allocated to be deleted, but I'm not sure. 回答1: You used one

问题 Suppose we have: int** myArray = new int*[100]; for(int i = 0; i < 100; i++){ myArray[i] = new int[3]; } What is the appropriate way to deallocate this array (which method below, if either is a correct way to do so)? 1. delete[] myArray; 2. for(int i = 0; i < 100; i++){ for(int j = 0; j < 3; j++){ delete myArray[i][j]; } } delete[] myArray; Intuitively it seems like we should do something like 2. since we want all of the memory we allocated to be deleted, but I'm not sure. 回答1: You used one

问题 Is std::array<int,10> (without myself using new ) guaranteed to be allocated in the stack rather then the heap by the C++-Standard? To be clear, I do not mean new std::array<int, 10> . I mainly wonder, if the standard library is allowed to use new inside its implementation. 回答1: I could not find more explicit answer in the standard, but [array.overview]/2: An array is an aggregate ( [dcl.init.aggr] ) that can be list-initialized with up to N elements whose types are convertible to T . And

问题 The code is as follow : #include <stdlib.h> int num = 3; // Static external variable int *ptr = &num; int main(void) { int num2 = 4; // Automatic variable int *ptr2 = &num2; free(ptr); //Free static variable free(ptr2); //Free automatic variable return 0; } I try to compile the above code and it works, I'm curious does the free() function able to free both the static variable and also automatic variable? Or basically it does nothing? 回答1: Calling free() on a pointer not returned by memory

问题 This question already has answers here : In what cases do I use malloc and/or new? (19 answers) Closed 2 years ago . #include <iostream> #include <cstdlib> using namespace std; class Box { public: Box() { cout << "Constructor called!" <<endl; } void printer(int x) { cout<<x<<" printer"<<endl; } ~Box() { cout << "Destructor called!" <<endl; } }; int main( ) { Box* myBoxArray = new Box[4]; Box* myBoxArray2 = (Box*)malloc(sizeof(Box[4])); myBoxArray2->printer(23); *myBoxArray2; *(myBoxArray2)

问题 I have this struct: struct foo { char *a; char *b; char *c; char *d; }; it's possible allocate space for struct itself and its members instead of e.g, struct foo f; f.a = malloc(); f.b = malloc(); f.c = malloc(); f.d = malloc(); strcpy(f.a, "a"); strcpy(f.b, "b"); //.. something like this(of couse that it doesn't works): struct foo f = malloc(sizeof(struct f)); strpcy(f.a, "a"); //etc 回答1: This is called a constructor. With error handling omitted, it may look like: struct foo *new_foo() {