realloc

Appending a value to the end of a dynamic array

由 ☆樱花仙子☆ 提交于 2019-12-11 11:16:43
问题 Well I have been studying a little C this winter break and in my adventures I stumbled upon an issue with a Dynamic Array. It's a fairly simple program really. What I am trying to do is to create an array that holds the numbers of the Fibonacci series. Here is the code: #include <stdio.h> #include <stdlib.h> int dynamic_arry_append(int* arry, int* number, int* size); int main() { int i, n, size = 3, *arry = NULL, fibarr[size]; printf("Dynamic array, Fibonacci series. \n"); printf("Capture

Why does a pointer have to be assigned for realloc to work without altering the first value in the memory block?

由 旧城冷巷雨未停 提交于 2019-12-11 09:44:47
问题 int *ptr; ... realloc(ptr,++count*sizeof(int)); or ptr=realloc(ptr,++count*sizeof(int)); I noticed if I use option number one more than once, the value of the first memory address (which ptr points to), becomes undefined (although all other values in the memory block are fine and can be accessed by subscripting ptr ). However, I assumed that all realloc does is either shrink or increase the size of a memory block, and ptr will still point to the same memory block and none of its values will

Using realloc to concat strings

由 ⅰ亾dé卋堺 提交于 2019-12-11 06:17:14
问题 I'm trying to concat two strings, supposing the "dest" string hasn't enough space to add another one, so I'm using dynamic arrays to solve it. The problem is a mremap_chunk error when trying to compile the code. I don't know what I'm missing since the realloc call has all the right params place in. Error: malloc.c:2869: mremap_chunk: Assertion `((size + offset) & (GLRO (dl_pagesize) - 1)) == 0' failed. Aborted (core dumped) #include <stdio.h> #include <string.h> #include <stdlib.h> char

Decreasing realloc

由 荒凉一梦 提交于 2019-12-11 01:07:10
问题 I have a few questions about understanding realloc behavior. #include <stdio.h> #include <stdlib.h> int main() { int *str; /* Initial memory allocation */ str = malloc(5 * sizeof(int)); *str = 1; *(str + 1) = 2; *(str + 2) = 3; *(str + 3) = 4; *(str + 4) = 5; /* Reallocating memory */ int i, j; for (i = 5; i > 0; i--) { str = realloc(str, i * sizeof(int)); for (j = 0; j < i; j++) { printf("%d", *(str + j)); } printf("\n"); } free(str); return(0); } In this code example, can I be sure that a

Realloc into a function

由 核能气质少年 提交于 2019-12-10 17:47:35
问题 My question is about 'realloc'. The following code works correctly (with no warning): #include <stdio.h> #include <stdlib.h> int main () { int num=10; int *vet; int i; for (i=0; i<num; i++) { /* allocate memory of vet to contains (i+1) int */ vet = (int*) realloc ( vet, (i+1) * sizeof(int) ); /* write numbers in the allocated memory */ vet[i] = 321 + i; } /* print test, if all works I must see: | 321 | 322 | 323 | 324 | 325 | 326 | 327 | 328 | 329 | 330 | */ printf ("| "); for (i=0; i<num; i+

realloc: invalid next size and malloc: memory corruption (fast)

由 走远了吗. 提交于 2019-12-10 17:44:40
问题 I am doing an exercise for fun from K and R C programming book. The program is for finding the longest line from a set of lines entered by the user and then prints it. Inputs: This is a test This is another long test this is another long testthis is another long test Observation: It runs fine for the first two inputs but fails for the larger string (3rd input) Errors: Error in `./longest': realloc(): invalid next size: 0x000000000246e010 *** Error in `./longest': malloc(): memory corruption

What happens if I re-alloc and the new size is 0. Is this equivalent with a free?

由 孤人 提交于 2019-12-10 12:54:57
问题 Given the following code: int *a = NULL; a = calloc(1, sizeof(*a)); printf("%d\n", a); a = realloc(a, 0); printf("%d\n", a); return (0); It returns: 4078904 0 Is this realloc equivalent to a free ? NOTE: I am using MinGW under WindowsXP. 回答1: Not necessarily. It often does as with the link that munissor posted, but the Mac OS 10.5 man page says: If size is zero and ptr is not NULL, a new, minimum sized object is allocated and the original object is freed. What is a "minimum sized object"?

VS2005中运行时库不一致导致项目编译出问题

由 守給你的承諾、 提交于 2019-12-09 15:45:57
我的工程中三个项目，编译其中的lib工程时是成功的，但是编译依赖于lib工程的第二个工程老出错， msvcprtd.lib(MSVCP80D.dll) : error LNK2005: ".......... LIBCMTD.lib(setlocal.obj) : error LNK2005: __configthreadlocale 已经在 MSVCRTD.lib(MSVCR80D.dll) 中定义 1>LIBCMTD.lib(dbgheap.obj) : error LNK2005: _malloc 已经在 MSVCRTD.lib(MSVCR80D.dll) 中定义 1>LIBCMTD.lib(dbgheap.obj) : error LNK2005: _realloc 已经在 MSVCRTD.lib(MSVCR80D.dll) 中定义 1>LIBCMTD.lib(dbgheap.obj) : error LNK2005: _free 已经在 MSVCRTD.lib(MSVCR80D.dll) 中定义 1>LIBCMTD.lib(dbgheap.obj) : error LNK2005: __CrtSetCheckCount 已经在 MSVCRTD.lib(MSVCR80D.dll) 中定义 1>LIBCMTD.lib(tidtable.obj) : error LNK2005

How much overhead do realloc calls introduce?

由 大憨熊 提交于 2019-12-08 16:42:08
问题 I am using realloc in every iteration of a for loop that iterates more that 10000 times. Is this a good practice? Will realloc cause an error if it was called a lot of times? 回答1: It won't fail unless you've run out of memory (which would happen with any other allocator as well) - but your code will usually run much quicker if you manage to estimate the required storage upfront. Often it's better to do an extra loop run solely to determine the storage requirements. I wouldn't say that realloc

Expand an array with realloc inside of a function - Pointers?

由 天大地大妈咪最大 提交于 2019-12-08 11:43:01
问题 I'm sure that the answer to this is me not understanding Pointers and References properly! So at the start of my C file I define a struct for people : typedef struct { char id[4]; int age; char name[128]; } people; Then inside of main() I create an array of 10 people structs called record . people* record = (people*)malloc(sizeof(people)* 10); In main() we start and then dive off into a function with MyFunction(record); (This function is prototyped at the beginning of the C file before main()
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