I have a small assignment in C. I am trying to create an array of pointers to a structure. My question is how can I initialize each pointer to NULL? Also, after I allocate memory for a member of the array, I can not assign values to the structure to which the array element points. #include <stdio.h> #include <stdlib.h> typedef str...
I know that it's a common convention to pass the length of dynamically allocated arrays to functions that manipulate them: void initializeAndFree(int* anArray, size_t length); int main(){ size_t arrayLength = 0; scanf("%d", &arrayLength); int* myArray = (int*)malloc(sizeof(int)*arrayLength); initializeAndFree(myArray, ...
I need help with debugging this piece of code. I know the problem is in malloc and free but can't find exactly where, why and how to fix it. Please don't answer: "Use gdb" and that's it. I would use gdb to debug it, but I still don't know much about it and am still learning it, and would like to have, in the meanwhile, another solution. ...
Dear Friends, I am trying to trace a segfault with valgrind. I get the following message from valgrind: ==3683== Conditional jump or move depends on uninitialised value(s) ==3683== at 0x4C277C5: sparse_mat_mat_kron (sparse.c:165) ==3683== by 0x4C2706E: rec_mating (rec.c:176) ==3683== by 0x401C1C: age_dep_iterate (age_dep.c:28...
I read somewhere that it is disastrous to use free to get rid of an object not created by calling malloc, is this true? why? ...
It's known that calloc differentiates itself with malloc in which it initializes the memory alloted. With calloc, the memory is set to zero. With malloc, the memory is not cleared. So in everyday work, i regard calloc as malloc+memset. Incidentally, for fun, i wrote the following codes for benchmark. The result is confused. Code 1: #in...
Okay so im finally to the point where I am testing my iPad App on an actual iPad... One thing that my app does is display a large (2mb) image in a scroll view. This is causing the iPad to get memory warnings. I run the app in the instruments to check for the leak. When I load the image, a leak is detected and i see the following in th...
My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = ...
Hi all, I have a structure defined like so: typedef struct { int n; int *n_p; void **list_pp; size_t rec_size; int n_buffs; size_t buff_size } fl_hdr_type; and in my code I Have a function for initlialization that has the following fl_hdr_type *fl_hdr; fl_hdr = malloc(sizeof(fl_hdr_type) + (buff_size_n * rec_size_n)); where ...
I am exploring the lower level workings of the system, and was wondering how malloc determines the start address of the heap. Is the heap at a constant offset or is there a call of some sort to get the start address? Does the stack affect the start address of the heap? ...
In glibc malloc.c or dlmalloc It said "repositioning tricks"As in blew, and use this trick in bin_at. bins is a array,the space is allocated when av(struct malloc_state) is allocated.doesn't it? the sizeof(bin[i]) is less then sizeof(struct malloc_chunk*)? When bin_at(M,1)(which is used as unsorted_chunks) is called,the result is: bin[...
I have a problem about malloc(). It is weird. My code is in the following. I use random generator to generate elements for an array. The array is opened by malloc(). If the array size is smaller than 8192, it is OK. If the size is larger than 8192, it shows segment fault. void random_generator(int num, int * array) { srand((unsigne...
Hey, I'm trying to convert a function I wrote to generate an array of longs that respresents Pascal's triangles into a function that returns an array of mpz_t's. However with the following code: mpz_t* make_triangle(int rows, int* count) { //compute triangle size using 1 + 2 + 3 + ... n = n(n + 1) / 2 *count = (rows * (rows + 1)) / 2; m...
I am transitioning to C++ from C. In C++, is there any use for the malloc function? Or can I just declare it with the "new" keyword. For example: class Node { ... } ... Node *node1 = malloc(sizeof(Node)); //malloc Node *node2 = new Node; //new Which one should I use? ...
I'm a bit new to malloc and C in general. I wanted to know how I can, if needed, extend the size of an otherwise fixed-size array with malloc. Example: #define SIZE 1000 struct mystruct { int a; int b; char c; }; mystruct myarray[ SIZE ]; int myarrayMaxSize = SIZE; .... if ( i > myarrayMaxSize ) { // malloc another SIZE (1000)...
I have a heap allocation error that I cant spot in my code that is picked up on vanguard/gdb on Linux but runs perfectly on a Windows cygwin environment. I understand that Linux could be tighter with its heap allocation than Windows but I would really like to have a response that discovers the issue/possible fix. I'm also aware that I ...
Hello i have the following error: malloc: * error for object 0x2087000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug I have no idea what object that is. I don't know how to find it. Can anybody explain to me how (and where) to use malloc_history. I have set a breakpoint in malloc_error_break b...
Why doesn't this print 5? void writeValue(int* value) { value = malloc(sizeof(int)); *value = 5; } int main(int argc, char * argv) { int* value = NULL; writeValue(value); printf("value = %d\n", *value); // error trying to access 0x00000000 } and how can I modify this so it would work while still using a pointer a...
I'm attempting to write a solver for a particular puzzle. It tries to find a solution by trying every possible move one at a time until it finds a solution. The first version tried to solve it depth-first by continually trying moves until it failed, then backtracking, but this turned out to be too slow. I have rewritten it to be breadth-...
I'm sure you (pros) can identify the bug's' in my code, I also would appreciate any other comments on my code. BTW, the code crashes after I run it. #include <stdlib.h> #include <stdio.h> #include <stdbool.h> typedef struct { int x; int y; } Location; typedef struct { bool walkable; unsigned char walked; // number of...