Most voted "pointer" questions
The tag can be used for the concept applied to any language. A pointer is a type of data that "points to" another value stored in memory using its address.
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answer59
viewsParentheses in a pointer to pointer
I’m studying a binary tree structure and I got in doubt in a part of the code. #include <stdio.h> #include <stdlib.h> typedef struct tree { int num; struct tree* sad; struct tree* sae; }…
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answer122
viewsHow to copy a structure pointer?
Is it possible to clone a structure pointer? Follow the code: typedef struct{ int numero; }estrutura; int main(int argc, char *argv[]){ estrutura *i = (estrutura *)malloc(sizeof(estrutura));…
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answer39
viewsConfusion in access to vector size in C bytes
In the code below: #include <stdio.h> void testaTamanhoVetor(int vetor[]) { printf("tamanho do vetor em bytes na funcao: %zu", sizeof(vetor)); } int main() { int a[10]; printf("tamanho do…
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answer44
viewsHow do I return a string from a char function? The returned value is NULL
I am having problems with creating a char function that returns a string typed by the user. I call her in a registration method and try to play for the struct variable. cadastrarLocacaoNome();…
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answers77
viewsMicro class system in C
What I would like is to automatically initialize a struct that receives function pointers. For example: struct teste{ int x; int y; int (*soma)(int, int); }; typedef struct teste Teste; int soma(int…
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answer263
viewsHow do I pass the first char address of a string to a function to write to it?
The problem is this: I made a function that takes the output of a given OS command and stores it in a string. The idea now would be to declare a single char string in my main function using malloc,…
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answers161
viewsPointer for C functions is not calling
I’m having a problem with function pointers. I declared the pointers and stored them in an array, but when calling the functions through the pointers the compiler has an error that I have not yet…
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answer131
viewsC pointers
Well, guys, I’m doing graph theory on C, and I tried to use dynamic allocation to create an array. Also, my code has a function to fill the matrix with 1 in the received indexes. But I have some…
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answers77
viewsHow to modify the content of a root using a pointer?
How to modify the contents of a root using a pointer? Write a code in C that uses a variable with the name 'root', have the type 'float' and have the initial value 3.1415. In this same code, use…
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answer70
viewsWhy is this C code not working (binary tree)?
Good morning, I’m trying to create a recursive function that traverses a binary tree and finds the largest integer contained in the nodes. My idea is to move to the function the pointer to the node…
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answer198
viewsC - How to pass an array in which it contains pointers to struct as a function parameter?
First I created a struct vector. Next I created a pointer vector, in which each element of this vector points to each element of the struct vector. Finally, I need to pass both (the struct vector…
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answers111
viewsPointers and matrices catching something unexpected
#include <stdio.h> int main() { int vetor[][3] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}; int valor= *(vetor[1] + 1) + **(vetor + 3); printf("%d", valor); } The code above was taken from…
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answer284
viewsStack operations
I am trying to do operations using stack but at the time of allocating the results in the previous position in stack is that I am not getting, because the result of operation is not allocated in the…
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answer84
viewsDoubt - Dynamic list
I have the following structure for my dynamic list: typedef struct DataNode { int id; } DataNode; typedef struct Node { DataNode data; struct Node *Next; } Node; typedef struct List { int size; Node…
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answer50
viewsValgrind problem and dynamic allocation in C++
I have a program a little bigger than that, I selected the part that I can not solve, are errors that seem unfounded, I’ve really tried everything. I imagine it’s a structural problem. I will post…
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answer55
viewsDoubt about pointer and matrix
Hello, I was trying to do an exercise in which you asked to print the address of each position of the matrix using pointer and I am in doubt if it is correct. I searched some videos on youtube and…
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answers141
viewsPython value and reference
Disregarding the way it was made, this is a square matrix transposition code, the person who did came across the error in assigning the values in the latter for and neither I or he could solve: when…
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answer84
viewsHow to resignify bytes without Undefined behavior?
Details In Assembly, C, C++, C# with unsafe and other languages it is possible to reinterpret binary code at the address as of different type from the original. Convert type int* for float* in C,…
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answers53
viewsWhat makes this C program unusable when compiled in different versions of GCC or Clang?
This C language program is compiled in all versions of GCC without any error message, but specifically in GCC 6.3 and 8.3, the executable produces totally inconsistent results. In GCC 8.1 and 10.2…
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answer63
viewsHow can we not access it with pointers?
I have a code where I create and then read a file .dat with information from sales records, such as date, time, price, etc. I can do a search by date, for example, and generate another file .dat…
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answer70
viewsDoubt about C++ pointers
Why if a char type raw pointer is pointing to some character of a std::string and print this pointer without the asterisk (*) it will show the rest of the string from the character it is pointing…
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answers23004
viewsHow to pass a struct vector by reference parameter?
My question is, what is the error of this passage? It seems that the passage (*dadosCliente+i) is incorrect, someone knows why? struct cliente{ char nome[50]; char endereco[50]; } void…
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answers84
viewsError accessing pointer
int main() { int**items[5]; for (int i=0;i<5;i++) { *items[i] = new int; <-- } return 0; } The program compiles, but does not run. I Debugger and pointed out that the error is where the arrow…
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answer324
viewsHow to pass a function pointer by parameter?
I need it passed through argv[], in the main function, the name of a function that will be called by the same. I can’t make comparisons of strings, then I must make the call with variables. Here is…
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answers264
viewsPointer return error in function
Guys, I’m making the following mistake: incompatible types when assigning to type 'char [30] ' from type 'char *' the code is as follows:: int main() { char *resultado[30]; float valor = 12735.98;…
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answer5855
viewsPointer of struct inside a struct
I cannot assign value to a variable of a pointer struct within a struct. My structs: typedef struct notas{ float geral; float especifica; }Notas; typedef struct data{ int dia,mes,ano; }Data; typedef…
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answers634
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answer161
viewsFunction that returns pointer gives crash when trying to return pointer to main program
I have this function that retrieves a record from a binary file already filled with records - such records are structured as Node - and returns it to the program. Only in the return of "i" for the…
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answer657
viewsSize of struct allocation
When declaring a normal variable of type int for example, the compiler goes there and, depending on the architecture, separates 4 bytes. struct exemplo{ int x; int b; }; int main(){ struct exemplo…
c++ pointer struct memory-management allocationasked 9 years, 11 months ago Alexsander Borgesdamaceno 541 -
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answer119
viewsPointer use
I need to use pointers, but I’m not sure how to express the syntax, it’s part of the goal of the task (change the value of the parameters passed by reference to the functions, such that these…
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answer207
viewsIs it correct to clean an internal malloc to a function with it?
Well given the following code is easy to do memory management: Code Example (in C): #include <stdio.h> #include <stdlib.h> int *criarValor(void){ int *valor = malloc(sizeof *valor);…
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answer629
viewsOpen a file using secondary function
I need to create a function that "points" a file pointer to a particular file in computer memory. I was able to do this: #include <stdio.h> void abre(FILE*); void procedimento(); int main () {…
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answers147
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answer418
viewsFunction int(*Cmp)(void*,void*)
I know it compares pointers and returns an integer that determines whether one is smaller than another, in order. But, when I will use it in main(), is giving some error. Can help me?…
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answers313
viewsHow to access the pointer of a struct within the pointer of another struct?
typedef struct vertice { int num_vertice; int profundidade; struct vertice **vertices_adja; } Vertice; typedef struct grafo { int qtd_vertices; int *Vertice; } Grafo; I want to access the attributes…
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answer112
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answer492
viewsUndefined Reference error when trying to use a template class
I have a class template Set and a menu class both with their respective . cpp and . hpp, when trying to use a cluster class pointer in my Menu class I get the following error: ||=== Build: Debug in…
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answers399
viewsDoubt about C pointers
void imprime (char *v, int n) { char *c; for (c = v; c < v + n; v++) printf ("%c", *c); } I have this function, but I don’t understand what exactly she’s doing and how the pointers behave in this…
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answer334
viewsOperator & and * in functions
What is the meaning of this & in front of the matrix (my function only works with &, I am overloading Cout<<(matriz1 + matriz2)) And the meaning also of the * in front of the void?!…
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answer175
viewsWhat is the increment on a pointer for?
Datum: #include <stdio.h> int main () { int x = 1; x++; int *y = &x; y = y + 1; printf("%d\n",x ); } The exit is 2. In that case I would like to know if the following interpretation is…
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answer1115
viewsProblem with split function in C
Hi, I’m studying the C language and came across a pointer problem in a string breaking function. I use the version GCC 4.8.4. The error value is "1234|123|123|123|123" 4/3/3/3, while other values…
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answer337
viewsError importing structs from a header file
I need to use the following structures without changing their file implementations .h. typedef unsigned long int chave_t; typedef unsigned long int conteudo_t; typedef struct entrada_hash{ chave_t…
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answer81
viewsHow can I pass a Descriptor file to another process?
Recently I read a post by Peter Hutterer explaining about a new protocol called inputfd that is intended to pass a file Descriptor directly to other processes without the interaction of the…
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answer94
viewsAccessing a pointer pointer ( c )
Why go down a level on the pointer ** lista / * lista we should use parentheses : ( * lista ), I asked the question because I saw in some examples on the internet that they didn’t use and also in an…
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answer208
viewsProblems with dynamic allocation and struct
I intend to create a struct where there will be a vector of structs... The way I thought of doing it was kind of like this: typedef struct{ char *teste_str; int teste_int; }TESTE_A; typedef struct{…
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answers1485
viewsProblems with function that returns character array in C++
Follows the code: #include <iostream> char* criaVetor(){ char vetor[20]="Olá mundo!"; return vetor; } int main(){ char retorno[20]=criaVetor; std::cout << retorno; return 0; } error:…
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answer317
viewsHelp with C nested structs
I was creating in C a list and using a struct, after finishing I tried to see what changed with a struct nestled, created two structs basic, one receiving only one value and another receiving this…
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answer1897
viewsHow to use pointer and vector in a single struct in C?
I cannot run a program that needs functions to execute a procedure, this function receives a vector of type struct by means of a pointer. There is no build error, but the program hangs while running…
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answers473
viewsDoubt char C pointer
Hello. I need to make a pointer char point to a memory position holding a phrase, in C. I’m doing like this: char *ptr; char array[3] = {'o','l','a'}; ptr = &array; But I don’t understand what’s…
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answer211
viewsHow to reference mat[x][y] in pointer notation
I’m working with programming in c, with pointers and dynamic allocation, need to respond to an exercise that asks for the following: How to reference mat[x][y] in pointer notation.…