I have written a simple c program as below where we are trying to read line by line data by using fgets() and we skipping the lines which doesn't start with character '$' , the problem I'm facing is I'm getting error as fgets: Cannot allocate memory at the 4th line and it is happening randomly
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#define MAX_BUFFER_SIZE_5000 5000
size_t CustomGetLine(char *dPtr, size_t *n, FILE *stream, char cStartChar,uint32_t offset )
{
char *result;
result = fgets(dPtr, *n, stream);
perror("fgets");
if (result != NULL)
{
offset += strlen(dPtr);
if (dPtr[0] != cStartChar)
{
return CustomGetLine(dPtr, n, stream, cStartChar, offset);
}
return strlen(dPtr);
}
return 0;
}
int main()
{
uint32_t u32Offset = 0, uPktlen = 0;
size_t PtrSize = MAX_BUFFER_SIZE_5000;
FILE *pCurrFile = fopen("test.txt", "r");
char *tempbuf = (char *)malloc(MAX_BUFFER_SIZE_5000);
if (pCurrFile != NULL && tempbuf != NULL)
{
fseek(pCurrFile, u32Offset, SEEK_SET);
while (uPktlen = CustomGetLine(tempbuf, &PtrSize, pCurrFile, '$', u32Offset))
{
printf("uPktlen before 0 = %d\n", uPktlen);
printf("%s\n", tempbuf);
u32Offset += uPktlen;
}
printf("uPktlen before 0 = %d\n", uPktlen);
fclose(pCurrFile);
}
else
{
printf("Error: Unable to open file or allocate memory.\n");
}
if (tempbuf != NULL)
{
free(tempbuf);
tempbuf = NULL;
}
return 0;
}
File Data is :
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What I have tried:
I have tried checking the heap memory, buffer overflow is also not happening since the data is within 2000 bytes.