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Data writes over after realloc


Data writes over after realloc

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Data writes over after realloc
Tag : c , By : wpoch
Date : November 23 2020, 01:01 AM

wish helps you Your code doesn't attempt to preserve the earlier questions. It always calls realloc() with a NULL pointer, resulting in a brand new allocation:
struct Question* questionsLocation = NULL;
/* ...there are no assignments to questionsLocation here... */
questionsLocation = (struct Question*)realloc(questionsLocation,
                                      *amountQuest * sizeof(struct Question));
struct Question* AddQuestions(int* amountQuest, struct Question* questionsLocation) {
    ...
    questionsLocation = (struct Question*)realloc(questionsLocation, ...);
    ...
    return questionsLocation;
}
int amountQuest = 0;
struct Question* questionsLocation = NULL;
...
questionsLocation = AddQuestion(&amountQuest, questionsLocation);

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realloc function that would work for memory allocated using new instead of realloc


Tag : cpp , By : Doug
Date : March 29 2020, 07:55 AM
To fix this issue No, there isn't. And frankly, if you are using new or new[]. your C++ code is probably not well designed. Look at using std::vector instead of new[], and at using values instead of new.

invalid realloc/realloc returns NULL


Tag : c , By : user181445
Date : March 29 2020, 07:55 AM
around this issue The problem is slightly subtle and caused by a combination of two things. Let's start here:
struct stos stosik;
struct stos* s;
s = &stosik;

name1(s);
void name1(struct stos* s)
{
    s = malloc (4 * sizeof (int));
}
int main()
    {
    struct stos* s = NULL;

    name1(s);

    if(s == NULL)
        return -1;
void name1(struct stos **s)
    {
    /* sanity check */
    if(s == NULL)
        return; 

    /* now, allocate enough space for four integers and make 
     * whatever s points to, point to that newly allocated
     * space.
     */
    *s = malloc(4 * sizeof(int));
}
struct stos *s = NULL;

/* we need to pass a pointer to s into name1, so get one. */
name1(&s);

/* malloc can fail; check the result! */
if(s == NULL) 
    return -1;
struct stos *name1()
{
    return malloc(4 * sizeof(int));
}
struct stos *s = name1();

/* malloc can fail; check the result! */
if(s == NULL)
    return -1;

realloc(): invalid next size - realloc dynamic struct


Tag : c , By : Vrki
Date : March 29 2020, 07:55 AM
around this issue When you see a backtrace involving malloc, realloc or free, it means your heap is corrupted: your program overwrote some data structures used by the memory management system. The most common causes for that are writing past the bounds of a block allocated by malloc (buffer overflow) and continuing to use a memory block allocated by malloc after calling free on it (use after free).
As Weather Vane already mentioned in a comment, the size you pass to malloc and realloc for s doesn't match your usage of s. s is a pointer to an array of struct fraze, and you use elements up to k of this array, so the memory block must be large enough for k+1 elements of type struct fraze. Given your allocation policy, that means you must leave room for i elements of type struct fraze. But your actual allocation is for only sizeof( int ) bytes, which is not enough.
s = malloc(i * sizeof(*s));
s_FRAZE *new_s = realloc(s, i * sizeof(*s));
if (new_s == NULL) {
    fputs("Out of memory!\n", stderr);
    exit(2);
}
s = new_s;

pointer being realloc'd was not allocated char* realloc in function


Tag : c , By : KT.
Date : March 29 2020, 07:55 AM
wish helps you I am learning pointers now, and i have some troubles with reallocating of char* in function. When i am running this code, i have this error. p.s. the one only goal of this code, it to understand how are pointers working. , C doesn't use assignment to copy strings.
When you do
first = "text";
strcpy(first, "text");
strcpy(*string, "otherText");

C11 - Realloc on array of structs fails when doing realloc twice


Tag : c , By : Alex Sadzawka
Date : September 27 2020, 08:00 AM
will help you I'm trying to use malloc and realloc to hold an array of structs. The array should dynamically grow, size should increase by 10 struct elements every time.
VocStruct = temp;
free(temp);
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