Questions tagged [pointers]
A pointer is a data type whose value refers directly to (or "points to") another value stored elsewhere in the computer memory using its address.
128
questions
1
vote
1answer
90 views
How to efficiently access public static variables/methods of the correct derived class?
I have an arbitrary number of derived classes all inheriting from the same base class. These derived classes all have the same static variables and static methods, although the implementations may ...
0
votes
2answers
229 views
Should I always allocate QObject and derived classes to the heap?
I was in #Qt irc channel, and I showed a small snippet of my code in a style that I heavily rely upon. It looks like this:
/* Get Reply from Server */
QPointer<QNetworkReply> reply;
{
...
2
votes
3answers
513 views
From a language design perspective, is the reference type in C++ mis-designed
Besides the fact that all primitive types of C++ are copy assignable except the reference type, it also doesn't play well with containers or any other parts of the language where copy-assignable ...
5
votes
1answer
2k views
Why do we need to specify the type of data a pointer will hold, if all pointers are the same [duplicate]
Why do we need to specify the type of the data whose address, a pointer will hold, if all pointers are the same.
Since all pointers store addresses.
Also, the amount of space a pointer will require in ...
-1
votes
1answer
157 views
Pointers and Values in C
I do a lot of work in various languages, most of which are scripting languages such as JavaScript, Shell Scripting, PHP and so on. But I do also work a lot with Java, which is closer to a more "real" ...
0
votes
2answers
780 views
What is the safest practice in handling QWidget pointer lifespan in a QObject oriented environment?
Consider the following constructor:
NetworkTools::NetworkTools(QObject *parent) : QObject(parent)
{
view = new QWebEngineView();
view->setParent(parent); // Produces an error, shown below.
...
3
votes
1answer
449 views
C++ Are members of a class pointer automatically on heap?
Let's say we have a struct Vector2i { int x = 0, int y = 0 };
And create a Pointer to it via Vector2i* pointer = new Vector2i;
Where would int x and int y be stored? Heap or stack?
Are all members ...
1
vote
2answers
169 views
Setting a pointer to NULL on failure?
I've been modifying some code written by a previous employee and came across a function with the following signature:
BOOL WINAPI PrependPadding(
_In_ SIZE_T cbPadding,
_In_ SIZE_T cbRow,
...
18
votes
3answers
928 views
When & why did pointers start to become viewed as risky?
It seems that there has been a gradual shift in thinking about the use of pointers in programming languages such that it became generally accepted that pointers were considered risky (if not outright "...
-1
votes
1answer
685 views
Why is it possible to access an array out of bounds with negative indexes much further than with positive indexes?
I have written two small programs in which I declare a very small array.
Then I try to access values out of bounds.
The interesting thing I noticed that when I try to decrement the index I can ...
26
votes
3answers
7k views
Why does a long int take 12 bytes on some machines?
I noticed something strange after compiling this code on my machine:
#include <stdio.h>
int main()
{
printf("Hello, World!\n");
int a,b,c,d;
int e,f,g;
long int h;
...
1
vote
1answer
112 views
What kind of pointer bug is this specifically?
UncommentatedPannen's (pannenkoek2012) newest video describes a glitch in the Nintendo 64 game Super Mario 64, which allows an object to push Mario out of bounds, which isn't normally possible, by ...
1
vote
2answers
655 views
How to avoid lots of ugly pointer casting when using a container in C?
Let's say I have a container in C, for example something similar to C++' std::deque:
struct deque
{
// blah
};
struct deque* deque_create(size_t element_size, size_t init_deq_size);
void* ...
2
votes
1answer
943 views
Should opaque pointers be pointers or types?
A common way to implement "PIMPL" in C is to do this:
typedef struct _Opaque Opaque;
Opaque* createOpaque();
void doSomething(Opaque *opaque);
Or:
typedef struct _Opaque* Opaque;
Opaque ...
6
votes
4answers
614 views
Refactor big C++ application to prevent from bad pointer
In application which has about 1.5 mln lines of code there is using many pointers as a class members and in other places in code. Classes are usually very huge.
It is possible to change to make it ...
-1
votes
1answer
283 views
GO - How to define methods of named type?
In GO, rule is, methods can be defined only on named type and pointer to named type.
In C, below code, operations are defined on type(say List),
typedef struct List List; //list.h
typedef struct {
...
3
votes
2answers
1k views
Type safety - GO vs C pointers
C is a static-typed language that is not type-safe, because pointers(void *y) let you do pretty much anything you like, even things that will crash your program.
GO is also a static typed language
...
1
vote
1answer
49 views
How to avoid fetching additional informations when instantiating objects
I'm creating an HTML5 game using javascript and have got some problems during the first instantiation of the objects of the scene.
Scenario
Self-written 2d game engine that supports multiple ...
1
vote
3answers
953 views
Is it possible to deliberately break RAM using pointers?
Is it possible to intentionally stress and break part of a computer on a mechanical level using the specificity of C/C++ in targeting addresses? All of this talk of addresses and pointers is not a ...
1
vote
3answers
802 views
What value does the byte pointed by null pointer have?
I know that long time ago computer scientists decided to treat all pointers to memory cell of address 0 as NULL. However, the memory cell at that address does exists after all, right? In that case, ...
1
vote
2answers
1k views
Struct “prototypes” in (plain)C?
As the title says, can it be done?
struct Room{
char *type; //Lecture hall, laboratory, etc.
char *name;
int *capacity; //How may people it can hold
struct Building *building;
};
...
7
votes
6answers
2k views
In C++; How big should an object [that will be transferred between functions] be before I consider delegating it to the heap?
In my day to day programming, I tend to use very few pointers, not only because I want to keep my code simple and error free, but because I assume that the programming that I do does not have any ...
3
votes
1answer
114 views
Why are pointers of structs not printed like pointers of variables? [closed]
Consider the following code:
package main
import "fmt"
type Vertex struct {
X, Y int
}
var (
i = 10
p = &i
v = Vertex{1,2}
q = &v
)
func main() {
fmt.Println(p) // ...
8
votes
6answers
1k views
In C, is * an operator, or part of a type in a declaration?
In C, * is called the indirection operator or the dereference operator. I understand how it works when it is used in a statement. It makes sense to write *p or * p, considering that it is a unary ...
0
votes
2answers
170 views
What's the difference between writing to the memory address of a declared int and writing directly to an int*?
I'm writing a program in which I fscanf a file and write to the same memory address repeatedly. I tried the following:
FILE *f = fopen(fname, "r");
int* num;
while(fscanf(f, "%d,", num) != EOF)
{
...
0
votes
2answers
777 views
Passing by refernce
I am trying to understand the ideas of pointers and references in C++. I am stuck with the following, what would be the specific behaviour in this case? I have a class like this:
class MyClass{
...
1
vote
0answers
287 views
Shared pointers across threads in UML for class and sequence diagrams
How does one represent shared pointers across threads in UML for class diagrams and sequence diagrams?
I especially want to document the ownership of the memory even though it's accessibility (a ...
7
votes
3answers
7k views
In C++, why shouldn't all function parameters be references?
I am currently learning C++ from the C++ Primer 5th edition. The book's chapter on functions states that only large objects (large being relative as standard library strings count, but "primitive ...
1
vote
1answer
175 views
Static memory idiom
I am on a micro controller (which means I can only have static memory allocation) and I am trying to work with inheritance.....
Suppose I have a abstract class Image and an abstract class Font. An ...
0
votes
1answer
510 views
How to call an unknown member function through an instance of a related class?
I have two classes. The first, called Game_Events, controls the objects and manages the general tasks. The second, called Button, is for one of those object instances.
The example below is wrong but ...
3
votes
4answers
931 views
When should a function take a pointer for a collection to fill vs returning a pointer with a filled collection?
In C++ I frequently see these two signatures used seemingly interchangeably:
void fill_array(Array<Type>* array_to_fill);
Array<Type>* filled_array();
I imagine there is a subtle ...
2
votes
3answers
1k views
Do I have to fork a server program as an “C” child process in order for correct interprocess communication to take place?
I would like to implement interprocess communication between an Ubuntu Linux 15.10 mono 4.1.2 C# recorder client and Ubuntu Linux 15.10 mono 4.1.2 C# video server using a C++ mutex class and C++ ...
3
votes
2answers
2k views
Is it possible to have pointers recursively point into themselves?
I have been learning C++ recently, and upon reading up on pointers I had a moment of thought.
I'm still attempting to grasp the very idea of pointers so excuse me if this doesn't make sense beyond ...
1
vote
2answers
209 views
Declaration confusion in pointers [closed]
I was just confused about the following declaration in C:
char **p[5]
I understand the char *p[] as an array of character pointers, but this one is puzzling me. Based on the precedence of [] over *, ...
0
votes
1answer
187 views
Containers and shared ownership within a class instance
I have two objects as member variables of a class.
std::unique_ptr<Object> specificObject;
std::vector<std::unique_ptr<Object>> objects;
I know that specificObject will always be ...
29
votes
10answers
11k views
Isn't the use of pointer variables a memory overhead?
In languages like C and C++, while using pointers to variables we need one more memory location to store that address. So isn't this a memory overhead? How is this compensated? Are pointers used in ...
7
votes
3answers
3k views
C++ returning persistent objects
I'm currently trying to learn best practices in C++ after coming from a C# background. I understand that there are three ways of handling objects:
By value (objects are copied or moved when passed ...
23
votes
4answers
4k views
Is a memory of all possible permutations of a kilobyte block and pointers possible?
This is a hard enough idea to wrap my head around and I would greatly appreciate any edits/help to get it more readable for those in-the-know.
Is it theoretically possible to have a hard drive that ...
4
votes
2answers
2k views
When is it ok to assert for a pointer being non-null?
This came up as part of a code review for a code segment which resembled this:
auto somePikachu = GetMeAPikachu();
NT_ASSERT(somePikachu != nullptr); // this only fires on debug build
somePikachu->...
0
votes
0answers
83 views
Checking for null pointers or allowing a math library to segfault?
I've been going through the GNU GSL design document and came across this interesting line in the Test suites section:
N.B. Don't bother to test for null pointers -- it's sufficient for the library ...
3
votes
3answers
941 views
Possible alternatives to copy constructors
In my C++ project I am relying on some libraries that do memory management for me. I make wrapper classes, for ease of use and memory safety, for example the class below. Note that this is a much ...
9
votes
1answer
2k views
Key / Value store development porting to modern C++
I am developing a database server similar to Cassandra.
Development were started in C, but things became very complicated without classes.
Currently I ported everything in C++11, but I am still ...
7
votes
3answers
2k views
Is it a common practice among professional programmers to avoid the use of raw pointers? [duplicate]
C++ tools and libraries have become more powerful than ever.
For instance, we can replace arrays by vectors. We can replace pointers by references. We can use smart-pointers.
Is it a common practice ...
1
vote
1answer
1k views
What does using pointer in Linux kernel imply?
So far I was under the perspective that while working in the kernel code, working with memory implies working with long integers and not pointers because dereferencing pointers shouldn't be done in ...
6
votes
1answer
6k views
What is the motivation for casting a pointer into a integer?
I'm doing some changes in the Linux kernel code and have noticed a pointer being cast into integer.
Check out buf below (full code):
snd_pcm_sframes_t snd_pcm_lib_read(struct snd_pcm_substream *...
4
votes
2answers
2k views
Why dynamic memory allocation functions in C returns void*?
Consider the prototypes of C's dynamic allocation functions
malloc - void* malloc(size_t size);
calloc - void* calloc(size_t n,size);
realloc - void* realloc(void* ptr,size_t newsize);
Now a ...
1
vote
2answers
373 views
shared or raw pointer c++
I am developing a noSQL database and currently moving the code from C to C++.
It have class Pair, which contains a raw pointer to a memory blob.
class Pair {
Blob* blob;
...
};
Then if you add ...
30
votes
10answers
23k views
What is the “type” of data that pointers hold in the C language?
I know that pointers hold addresses. I know that pointers' types are "generally" known based on the "type" of data they point to. But, pointers are still variables and the addresses they hold must ...
1
vote
0answers
393 views
Why C doesn't have better notation for pointers? [duplicate]
The * symbol is used for three different purposes
multiplication
Pointer declaration
Pointer dereferencing.
Why designers of C kept this notation? In other words, wouldn't it be nice if there was ...
1
vote
2answers
762 views
“Sweep” a vector of pointers
I'm using a vector to store pointers to objects. In some cases I destroy one or more of these objects (setting the vector spaces to NULL after each delete call), which are externally selected:
for (...
