C valgrind大小为8的读取无效
我试图理解Valgrind报告“大小为4的无效读取”错误的原因。在Linux控制台上编译代码并给出正确的输出。C valgrind大小为8的读取无效,c,valgrind,C,Valgrind,我试图理解Valgrind报告“大小为4的无效读取”错误的原因。在Linux控制台上编译代码并给出正确的输出。 我们的目标是构建一个动态的结构记录数组(最多10Mil项),这些记录动态增长,并通过结构列表按语言进行组织 代码: #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <unistd.h> #incl
我们的目标是构建一个动态的结构记录数组(最多10Mil项),这些记录动态增长,并通过结构列表按语言进行组织 代码:
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include "../crc64.c"
typedef struct {
char cat;
uint64_t crc;
int id;
} record;
typedef struct {
int count;
char *lang;
record **records;
} list;
record *records = NULL;
int record_count = 0;
list *lists = NULL;
int list_count = 0;
void addItemToList(record *r, char *lang){
int found = 0;
for(int i = 0; i<list_count; i++){
if(strcmp(lists[i].lang, lang) == 0){
list *l = &lists[i];
found = 1;
record **tmp = realloc(l->records, (l->count + 1) * sizeof(record *));
if (tmp == NULL)
printf("Problem on realloc - records/list\n");
else{
l->records = tmp;
l->count ++;
l->records[l->count -1] = r;
}
break;
}
}
if(found == 0){
list_count ++;
list *tmp = realloc(lists, list_count * sizeof(list));
if(!tmp)
printf("Error on realloc - list");
lists = tmp;
lists[list_count - 1].count =1 ;
lists[list_count - 1].lang = lang ;
record **tmp1 = realloc(NULL, sizeof(record *));
if(!tmp1)
printf("Error on realloc records/list \n");
lists[list_count - 1].records = tmp1;
tmp1[0] = r;
}
}
int addRecord(char cat, char *name, int id, char lang[3]){
record *tmp;
if(record_count == 0){
tmp = malloc(1 * sizeof(record));
}
else
tmp = realloc(records, (record_count + 1) * sizeof(record));
if(tmp == NULL){
printf("Error on m(re)alloc records\n");
return(1);
}
records = tmp;
record r = {cat, crc64(name), id};
records[record_count ] = r;
addItemToList(&(records[record_count]), lang);
record_count ++;
return 0;
}
int main(void){
addRecord('l', "torino",1, "it");
addRecord('l', "berlin",20, "de");
addRecord('l', "paris",30, "fr");
addRecord('l', "hamburg",21, "de");
addRecord('l', "sassari",2, "it");
addRecord('l', "cagliari",3, "it");
addRecord('l', "milano",4, "it");
for(int i=0; i< list_count;i++){
printf("lang: %s, count :%d\n", lists[i].lang, lists[i].count);
for (int z = 0; z < lists[i].count; z ++){
printf(" crc: %lu - id: %d \n", lists[i].records[z]->crc, lists[i].records[z]->id);
}
}
return 0;
}
您正在重新分配记录,但不更新指针
tmp = realloc(records, (record_count + 1) * sizeof(record));
执行此操作时,指向旧记录的所有指针数组将变得无效。
下面是一个简单的例子
record *array = malloc(sizeof(*array));
record *r1 = &array[0];
array = realloc(array, sizeof(*array) * 2);
record *r2 = &array[1];
// r1 is probably invalid, since 'array' changed
有几种方法可以解决这个问题
当您realloc
时,检查并更新所有指针。这真的很痛苦
分别分配每个记录,而不是在一个大数组中。(不,这不会浪费内存。至少与由于字段顺序而浪费的每条记录的8字节相比是如此。)
在记录数组中使用索引,而不是指向记录的指针。这些不需要更新
谢谢,alloc每一张唱片都很好用。大约第三点,您的意思是只在列表中存储大数组中记录的位置吗?。在这种情况下,使用qsort会发生什么?在这种情况下,位置会丢失吗?
record *array = malloc(sizeof(*array));
record *r1 = &array[0];
array = realloc(array, sizeof(*array) * 2);
record *r2 = &array[1];
// r1 is probably invalid, since 'array' changed