Facing issue when printing the data that is updated in malloc. In the below code am creating a string Test.DataType_1.Tag_1 …. Test.DataType_1.Tag_20 in create_tags() function, when the data is updated properly and printed i create_tags() function it prints properly but if printed in main() function in for loop data is distorted.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define NUM_OF_TAGS (20)
#define NUM_DATA_TYPES (01)
#define MAX_SUBSCRIPTION (1)
#define MAX_MONITORED_ITEMS (2)
#define MAX_ITEMS_TO_CREATE (20)
typedef struct
{
char nodeID[50];
}TAG_NAME;
typedef struct
{
int32_t group_id;
TAG_NAME *tag;
}GROUP;
int32_t max_subscription;
int32_t max_monitored_item;
int32_t max_item_to_create;
void create_tags(GROUP *node)
{
char t_node[50];
char r_node[50];
memset(r_node, 0, sizeof(r_node));
memset(t_node, 0, sizeof(t_node));
for(int i = 1; i <= NUM_OF_TAGS; i++)
{
sprintf(t_node, "Test.DataType_1.Tag_%d", i);
strcat(r_node, t_node);
strcpy(node->tag[i].nodeID, r_node);
printf("%sn", node->tag[i].nodeID);
memset(t_node, 0, sizeof(t_node));
memset(r_node, 0, sizeof(r_node));
}
}
int main(void)
{
max_subscription = MAX_SUBSCRIPTION;
max_monitored_item = MAX_MONITORED_ITEMS;
max_item_to_create = MAX_ITEMS_TO_CREATE;
GROUP *group = NULL;
/* Grouping Nodes */
group = malloc(sizeof(GROUP) * max_subscription * max_monitored_item);
for(int j = 0; j < max_subscription * max_monitored_item; j++)
{
group[j].tag = malloc(sizeof(GROUP) * max_item_to_create);
memset(group[j].tag, 0, sizeof(GROUP) * max_item_to_create);
printf("########## Set %d: Start ###########n", j);
group[j].group_id = j;
create_tags(&group[j]);
printf("########## End %d: Start ###########n", j);
printf("n");
}
int32_t count = 0;
for(int32_t i = 0; i < max_subscription; i++)
{
for(int32_t j = 0; j < max_monitored_item; j++)
{
printf("============= Start: %d ===============n", count );
for (int32_t k = 0; k < max_item_to_create; k++)
{
printf("%sn", group[count].tag[k].nodeID);
}
printf("============= End: %d ===============n", count);
count++;
}
}
}
The output of the code is follows, when i print the data inside create_tags() function, the data populated is correctly printed here am printing the same data twice.
But when i print the same in loops it get distorted in printf("%sn", group[count].tag[k].nodeID);
########## Set 0: Start ########### Test.DataType_1.Tag_1 Test.DataType_1.Tag_2 Test.DataType_1.Tag_3 Test.DataType_1.Tag_4 Test.DataType_1.Tag_5 Test.DataType_1.Tag_6 Test.DataType_1.Tag_7 Test.DataType_1.Tag_8 Test.DataType_1.Tag_9 Test.DataType_1.Tag_10 Test.DataType_1.Tag_11 Test.DataType_1.Tag_12 Test.DataType_1.Tag_13 Test.DataType_1.Tag_14 Test.DataType_1.Tag_15 Test.DataType_1.Tag_16 Test.DataType_1.Tag_17 Test.DataType_1.Tag_18 Test.DataType_1.Tag_19 Test.DataType_1.Tag_20 ########## End 0: Start ########### ########## Set 1: Start ########### Test.DataType_1.Tag_1 Test.DataType_1.Tag_2 Test.DataType_1.Tag_3 Test.DataType_1.Tag_4 Test.DataType_1.Tag_5 Test.DataType_1.Tag_6 Test.DataType_1.Tag_7 Test.DataType_1.Tag_8 Test.DataType_1.Tag_9 Test.DataType_1.Tag_10 Test.DataType_1.Tag_11 Test.DataType_1.Tag_12 Test.DataType_1.Tag_13 Test.DataType_1.Tag_14 Test.DataType_1.Tag_15 Test.DataType_1.Tag_16 Test.DataType_1.Tag_17 Test.DataType_1.Tag_18 Test.DataType_1.Tag_19 Test.DataType_1.Tag_20 ########## End 1: Start ########### ============= Start: 0 =============== Test.DataType_1.Tag_1 Test.DataType_1.Tag_2 Test.DataType_1.Tag_3 Test.DataType_1.Tag_4 Test.DataType_1.Tag_5 Test.DataType_1.Tag_6 1.Tag_6 =============== Test.DataType_1.Tag_8 Test.DataType_1.Tag_9 Test.DataType_1.Tag_10 Test.DataType_1.Tag_11 Test.DataType_1.Tag_12 Test.DataType_1.Tag_13 Test.DataType_1.Tag_14 Test.DataType_1.Tag_15 Test.DataType_1.Tag_16 Test.DataType_1.Tag_17 Test.DataType_1.Tag_18 Test.DataType_1.Tag_19 ============= End: 0 =============== ============= Start: 1 =============== Test.DataType_1.Tag_1 Test.DataType_1.Tag_2 Test.DataType_1.Tag_3 Test.DataType_1.Tag_4 Test.DataType_1.Tag_5 Test.DataType_1.Tag_6 Test.DataType_1.Tag_7 Test.DataType_1.Tag_8 Test.DataType_1.Tag_9 Test.DataType_1.Tag_10 Test.DataType_1.Tag_11 Test.DataType_1.Tag_12 Test.DataType_1.Tag_13 Test.DataType_1.Tag_14 Test.DataType_1.Tag_15 Test.DataType_1.Tag_16 Test.DataType_1.Tag_17 Test.DataType_1.Tag_18 Test.DataType_1.Tag_19 ============= End: 1 ===============
Any hint as to why this is happening will be helpful.
Advertisement
Answer
In your main function, you allocate both the group array, and the tag array within it, with an element size of sizeof(GROUP). In addition, you use that same size when zeroing out the tag array:
group = malloc(sizeof(GROUP) * max_subscription * max_monitored_item); group[j].tag = malloc(sizeof(GROUP) * max_item_to_create); memset(group[j].tag, 0, sizeof(GROUP) * max_item_to_create);
Since GROUP consists of an integer and pointer, it’s almost certainly going to be smaller that the 50-byte TAG_NAME. That would mean you don’t allocate enough space for it, probably leading to buffer overruns in the memory arena later on, where your code assumes it has enough space.
You should use sizeof(TAG_NAME) when allocating (and zeroing) the tag array. But, given you want to zero-initialise it, you may want to use calloc instead of the malloc/memset combo:
group[j].tag = calloc(max_item_to_create, sizeof(TAG_NAME));