C-string memory allocation, table of C-strings [duplicate] - c

Question

This question already has answers here:
How C strings are allocated in memory?
(5 answers)
Closed 8 years ago.
I want to make dynamically allocated c-string table, but I think i don't understand the topic very well, could You explain it to me or correct my code?
#include <stdio.h>
int main()
{
int i;
char** t;
t=(char**)malloc(16*sizeof(char*));
for(i<0;i<100;i++)
{
*t[i]=(char*)malloc(16*sizeof(char));
}
return 0;
}

Answer 1

You should use variables for everything you want. For example, you allocate a memory for 16 elements of type char* and, as a result, you have an array with 16 elements, but then you are going from 0 to 100 ? Why ?
#include <stdio.h>
int main()
{
int n = 16;
int m = 16;
// Allocate a memory for n elements of type char*
char** t = (char**)malloc(n * sizeof(char*));
for(int i = 0; i < n; ++i)
{
// For each element in array t - initialize with another array.
// Allocate m elements of type char
t[i] = (char*)malloc(m * sizeof(char));
// Initialize
for(int j = 0; j < m; ++j)
t[i][m] = 'a';
}
// Print
for(int i = 0; i < n; ++i)
{
for(int j = 0; j < m; ++j)
printf("%c ", t[i][m]);
printf("\n");
}
// Free allocated memory!
for(int i = 0; i < n; ++i)
free(t[i]);
free(t);
return 0;
}

Answer 2

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
int main(int I__argC, char *I__argV[])
{
int rCode=0;
int i;
char **t=NULL;
size_t arraySize;
/* Parse command line args. */
if(2 != I__argC)
{
rCode=EINVAL;
printf("USAGE: %s {dynamic array size}\n", I__argV[0]);
goto CLEANUP;
}
arraySize=strtoul(I__argV[1], NULL, 0);
if(0 == arraySize)
{
rCode=EINVAL;
fprintf(stderr, "Cannot allocate a dynamic array of size zero.\n");
goto CLEANUP;
}
/* Allocate a dynamic array of string pointers. */
errno=0;
t = malloc(arraySize * sizeof(*t));
if(NULL == t)
{
rCode = errno ? errno : ENOMEM;
fprintf(stderr, "malloc() failed.\n");
goto CLEANUP;
}
memset(t, 0, arraySize * sizeof(*t));
/* Initialize each pointer with a dynamically allocated string. */
for(i=0; i<arraySize; i++)
{
errno=0;
t[i]=strdup("A string");
if(NULL == t[i])
{
rCode= errno ? errno : ENOMEM;
fprintf(stderr, "strdup() failed.\n");
goto CLEANUP;
}
}
CLEANUP:
/* Free the array of pointers, and all dynamically allocated strings. */
if(t)
{
for(i=0; i<arraySize; i++)
{
if(t[i])
free(t[i]);
}
free(t);
}
return(rCode);
}

Answer 3

Your code can be corrected so that it can create 100X16 character table or table with 100 string of 16 char length.
#include <stdio.h>
#include <stdlib.h>
int main()
{
int i;
int noOfStrings = 100;
int eachStringLenght = 16;
char** t;
t=(char**)malloc(noOfStrings*sizeof(char*));
for(i=0;i<noOfStrings;i++)
{
t[i]=(char*)malloc(eachStringLenght*sizeof(char));
}
return 0;
}