All Questions
22,934
questions
3911
votes
44
answers
1.2m
views
What are the differences between a pointer variable and a reference variable?
What is the difference between a pointer variable and a reference variable?
- 59.4k
3125
votes
12
answers
775k
views
When should static_cast, dynamic_cast, const_cast, and reinterpret_cast be used?
What are the proper uses of:
static_cast
dynamic_cast
const_cast
reinterpret_cast
(type)value (C-style cast)
type(value) (function-style cast)
How does one decide which to use in which specific ...
- 118k
2164
votes
14
answers
732k
views
What is a smart pointer and when should I use one?
What is a smart pointer and when should I use one?
- 96.7k
2046
votes
8
answers
911k
views
Regular cast vs. static_cast vs. dynamic_cast [duplicate]
I've been writing C and C++ code for almost twenty years, but there's one aspect of these languages that I've never really understood. I've obviously used regular casts i.e.
MyClass *m = (MyClass *)...
- 56.7k
1894
votes
24
answers
425k
views
Why should I use a pointer rather than the object itself?
I'm coming from a Java background and have started working with objects in C++. But one thing that occurred to me is that people often use pointers to objects rather than the objects themselves, for ...
- 16.4k
1809
votes
23
answers
733k
views
What is the difference between const int*, const int * const, and int const *?
I always mess up how to use const int*, const int * const, and int const * correctly. Is there a set of rules defining what you can and cannot do?
I want to know all the do's and all don'ts in terms ...
ultraman
693
votes
6
answers
808k
views
What does 'dereferencing' a pointer mean in C/C++?
Please include an example with the explanation.
- 13.1k
668
votes
14
answers
406k
views
What is the nullptr keyword, and why is it better than NULL?
We now have C++11 with many new features. An interesting and confusing one (at least for me) is the new nullptr.
Well, no need anymore for the nasty macro NULL.
int* x = nullptr;
myclass* obj = ...
- 95.6k
570
votes
6
answers
606k
views
Typedef function pointer?
I'm learning how to dynamically load DLL's but what I don't understand is this line
typedef void (*FunctionFunc)();
I have a few questions. If someone is able to answer them I would be grateful.
...
- 6,705
515
votes
5
answers
142k
views
How do I use arrays in C++?
C++ inherited arrays from C where they are used virtually everywhere. C++ provides abstractions that are easier to use and less error-prone (std::vector<T> since C++98 and std::array<T, n> ...
- 260k
496
votes
11
answers
108k
views
What is array-to-pointer conversion aka. decay?
What is array-to-pointer conversion aka. decay? Is there any relation to array pointers?
- 5,973
476
votes
15
answers
55k
views
How many levels of pointers can we have?
How many pointers (*) are allowed in a single variable?
Let's consider the following example.
int a = 10;
int *p = &a;
Similarly we can have
int **q = &p;
int ***r = &q;
and so on.
...
- 7,876
470
votes
28
answers
92k
views
What are the barriers to understanding pointers and what can be done to overcome them? [closed]
Why are pointers such a leading factor of confusion for many new, and even old, college-level students in C or C++? Are there any tools or thought processes that helped you understand how pointers ...
462
votes
17
answers
250k
views
When should I use pointers instead of references in API-design?
I understand the syntax and general semantics of pointers versus references, but how should I decide when it is more-or-less appropriate to use references or pointers in an API?
Naturally some ...
- 7,341
461
votes
17
answers
382k
views
Why use pointers? [closed]
I know this is a really basic question, but I've just started with some basic C++ programming after coding a few projects with high-level languages.
Basically I have three questions:
Why use ...
Anonymous
449
votes
19
answers
1.1m
views
Passing a 2D array to a C++ function
I have a function which I want to take, as a parameter, a 2D array of variable size.
So far I have this:
void myFunction(double** myArray){
myArray[x][y] = 5;
etc...
}
And I have ...
- 4,493
397
votes
17
answers
547k
views
How to find the size of an array (from a pointer pointing to the first element array)?
First off, here is some code:
int main()
{
int days[] = {1,2,3,4,5};
int *ptr = days;
printf("%u\n", sizeof(days));
printf("%u\n", sizeof(ptr));
return 0;
}
Is there a way to ...
- 4,529
355
votes
12
answers
182k
views
When should I use the new keyword in C++? [duplicate]
I've been using C++ for a short while, and I've been wondering about the new keyword. Simply, should I be using it, or not?
With the new keyword...
MyClass* myClass = new MyClass();
myClass-&...
- 39k
352
votes
6
answers
332k
views
352
votes
9
answers
215k
views
Is it safe to delete a NULL pointer?
Is it safe to delete a NULL pointer?
And is it a good coding style?
- 5,897
351
votes
4
answers
302k
views
NULL vs nullptr (Why was it replaced?) [duplicate]
I know that in C++ 0x or NULL was replaced by nullptr in pointer-based applications. I'm just curious of the exact reason why they made this replacement?
In what scenario is using nullptr over NULL ...
- 5,352
345
votes
4
answers
319k
views
Differences between unique_ptr and shared_ptr [duplicate]
Possible Duplicates:
pimpl: shared_ptr or unique_ptr
smart pointers (boost) explained
Could someone explain differences between shared_ptr and unique_ptr?
- 16.8k
321
votes
19
answers
217k
views
What is a pointer to class data member "::*" and what is its use?
I came across this strange code snippet which compiles fine:
class Car
{
public:
int speed;
};
int main()
{
int Car::*pSpeed = &Car::speed;
return 0;
}
Why does C++ have this ...
- 77.4k
296
votes
21
answers
1.1m
views
Return array in a function
I have an array int arr[5] that is passed to a function fillarr(int arr[]):
int fillarr(int arr[])
{
for(...);
return arr;
}
How can I return that array?
How will I use it, say I returned a ...
- 13.4k
288
votes
7
answers
161k
views
Are there benefits of passing by pointer over passing by reference in C++?
What are the benefits of passing by pointer over passing by reference in C++?
Lately, I have seen a number of examples that chose passing function arguments by pointers instead of passing by ...
- 8,831
278
votes
12
answers
129k
views
Should I use a pointer or a reference to remotely assign a variable? [duplicate]
What would be better practice when giving a function the original variable to work with:
unsigned long x = 4;
void func1(unsigned long& val) {
val = 5;
}
func1(x);
or:
void ...
- 2,791
273
votes
8
answers
148k
views
How should I pass objects to functions?
I am new to C++ programming, but I have experience in Java. I need guidance on how to pass objects to functions in C++.
Do I need to pass pointers, references, or non-pointer and non-reference values?...
- 8,325
270
votes
9
answers
106k
views
Should I use static_cast or reinterpret_cast when casting a void* to whatever
Both static_cast and reinterpret_cast seem to work fine for casting void* to another pointer type. Is there a good reason to favor one over the other?
- 3,134
256
votes
17
answers
155k
views
Is the sizeof(some pointer) always equal to four?
For example:
sizeof(char*) returns 4. As does int*, long long*, everything that I've tried. Are there any exceptions to this?
- 15.4k
245
votes
4
answers
41k
views
Which kind of pointer do I use when?
Ok, so the last time I wrote C++ for a living, std::auto_ptr was all the std lib had available, and boost::shared_ptr was all the rage. I never really looked into the other smart pointer types boost ...
- 222k
207
votes
14
answers
137k
views
Can I use if (pointer) instead of if (pointer != NULL)?
Is it safe to check a pointer to not being NULL by writing simply if(pointer) or do I have to use if(pointer != NULL)?
- 33.4k
207
votes
3
answers
37k
views
Why is 'this' a pointer and not a reference?
I was reading the answers to this question C++ pros and cons and got this doubt while reading the comments.
programmers frequently find it confusing that "this" is a pointer but not a ...
- 75.7k
204
votes
2
answers
194k
views
How to cast/convert pointer to reference in C++
How can I pass a pointer (Object *ob) to a function which prototype is void foo(Object &) ?
- 13.8k
185
votes
18
answers
118k
views
Is it good practice to NULL a pointer after deleting it?
I'll start out by saying, use smart pointers and you'll never have to worry about this.
What are the problems with the following code?
Foo * p = new Foo;
// (use p)
delete p;
p = NULL;
This was ...
- 304k
174
votes
6
answers
99k
views
Declaring pointers; asterisk on the left or right of the space between the type and name? [duplicate]
Possible Duplicates:
What makes more sense - char* string or char *string?
Pointer declarations in C++: placement of the asterisk
I've seen mixed versions of this in a lot of code. (This ...
- 4,549
169
votes
10
answers
66k
views
Should I store entire objects, or pointers to objects in containers?
Designing a new system from scratch. I'll be using the STL to store lists and maps of certain long-live objects.
Question: Should I ensure my objects have copy constructors and store copies of ...
- 19.9k
162
votes
8
answers
28k
views
Why do C++ libraries and frameworks never use smart pointers?
I read in a few articles that raw pointers should almost never be used. Instead they should always be wrapped inside smart pointers, whether it's scoped or shared pointers.
However, I noticed that ...
- 89.5k
159
votes
17
answers
37k
views
What's the point of const pointers?
I'm not talking about pointers to const values, but const pointers themselves.
I'm learning C and C++ beyond the very basic stuff and just until today I realized that pointers are passed by value to ...
- 1,693
158
votes
12
answers
111k
views
Pointer expressions: *ptr++, *++ptr and ++*ptr
Recently I have come across this problem which I am unable to understand by myself.
What do these three Expressions REALLY mean?
*ptr++
*++ptr
++*ptr
I have tried Ritchie. But unfortunately was ...
- 1,325
153
votes
4
answers
71k
views
What is the difference between std::reference_wrapper and a simple pointer?
Why is there a need to have std::reference_wrapper? Where should it be used? How is it different from a simple pointer? How its performance compares to a simple pointer?
- 3,015
152
votes
10
answers
175k
views
Passing references to pointers in C++
As far as I can tell, there's no reason I shouldn't be allowed to pass a reference to a pointer in C++. However, my attempts to do so are failing, and I have no idea why.
This is what I'm doing:
...
- 15.1k
149
votes
12
answers
15k
views
Why is x[0] != x[0][0] != x[0][0][0]?
I'm studying a little of C++ and I'm fighting with pointers. I understand that I can have 3 level of pointers by declaring:
int *(*x)[5];
so that *x is a pointer to an array of 5 elements that are ...
- 1,741
148
votes
16
answers
135k
views
How does delete[] know it's an array?
Alright, I think we all agree that what happens with the following code is undefined, depending on what is passed,
void deleteForMe(int* pointer)
{
delete[] pointer;
}
The pointer could be all ...
- 1,821
142
votes
4
answers
222k
views
How to declare std::unique_ptr and what is the use of it?
I try to understand how std::unique_ptr works and for that I found this document. The author starts from the following example:
#include <utility> //declarations of unique_ptr
using std::...
- 128k
140
votes
15
answers
50k
views
Placement of the asterisk in pointer declarations
I've recently decided that I just have to finally learn C/C++, and there is one thing I do not really understand about pointers or more precisely, their definition.
How about these examples:
int* ...
- 179k
138
votes
7
answers
122k
views
What can I use instead of the arrow operator, `->`?
What is the arrow operator (->) a synonym for?
- 11.1k
138
votes
14
answers
15k
views
Why are function pointers and data pointers incompatible in C/C++?
I have read that converting a function pointer to a data pointer and vice versa works on most platforms but is not guaranteed to work. Why is this the case? Shouldn't both be simply addresses into ...
- 39.2k
137
votes
9
answers
31k
views
Why does the use of 'new' cause memory leaks?
I learned C# first, and now I'm starting with C++. As I understand, operator new in C++ is not similar to the one in C#.
Can you explain the reason of the memory leak in this sample code?
class A { ....
user1131997
135
votes
2
answers
54k
views
Can I call memcpy() and memmove() with "number of bytes" set to zero?
Do I need to treat cases when I actully have nothing to move/copy with memmove()/memcpy() as edge cases
int numberOfBytes = ...
if( numberOfBytes != 0 ) {
memmove( dest, source, numberOfBytes );
}...
- 169k
135
votes
21
answers
46k
views
Why is address zero used for the null pointer?
In C (or C++ for that matter), pointers are special if they have the value zero: I am adviced to set pointers to zero after freeing their memory, because it means freeing the pointer again isn't ...
- 3,357