C binary program for prime numbers does not want to run - c

Question

I've a problem at the execution of my program.
I compile it with gcc using: gcc -std=c89 -Wall -Wextra -lm main.c.
Same problem with clang and I didn't try it with tcc yet but I will when the program will be finished.
I would like it to be compilable with a c89 compiler, this explains some of my choices. I've no error at the compilation but a problem at the execution.
Like what's written in some of my comments in my code, at the execution normally, I would have an error because of a division by 0 (with the k variable) but I think I have an error in the "do...while" loop (because the rest of my function is tested), and before the by k division.
I took some hours to debug (especially with gdb (-g option add to the compilation command and run -v in gdb) but I'm still blocked.
/*librairies*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/*main function*/
int main(){
int N, b, i, j, h, k;
int *t; /*pointer which will become an array (see in another after comment)*/
float l, m, a;
k = 0; /*Problem with k because we will see later an error*/
printf("Your number : ");
scanf("%d", &N);
if (N>1){
a = sqrt(N);
b = a; /*we convert float into int and it rounds under, normal*/
t = malloc(N * sizeof(int)); /*manual dynamic memory allocation for the array to respect C89*/
if (t==NULL){ /*t is null when you have not enough ram for a too big value for N*/
exit(0);
}
for (i=1;i<N;i++){ /*function to fill the array with 2,3..N*/
j = i + 1;
h = i - 1;
t[h] = j;
}
do{
if (t[k]==0){
k = k + 1;
} else{
for (i=1;i<N;i++){ /*problem nearby, because the division by 0 error does not come know at the execution = 0*/
h = i - 1;
if (t[h]!=0){
l = (float)t[h] / (float)k; /*It's going to be a problem because in the first loop, k = 0*/
m = l - (int)l;
if (m==0.0f){
t[h] = 0;
}
}
}
}
} while (k<b);
h = 0;
for (i=1;i<N;i++){
h = i - 1;
printf("%d\n", t[h]); /*printf to test before continuing the program*/
}
} else{
printf("Your number is not valid\n");
}
return 0;
}
Info: This program is just a personnal project to illustrate for me a math course I had (about prime numbers, and for know with the problem solved and the k problem solved, it should display:
Your number: N /*N is a valid (positive integer) stdin input*/
0 /*and 0 until the k<b prime values are passed but I will make them to be displayed*/
a prime number
0
the next prime number
0
the next prime number
0
the next prime number
0
the next prime number
0
.
.
the last prime number (which can be N if N is a prime one)
The theorem used for this program is:
You choose a number
You calculate its square root
1, here is not a considered prime number because it divides all prime
numbers.
You write all the numbers from 2 to the number you choose
You remove every multiples of prime numbers (the prime numbers used here are those under the square root) every where in the written list (here an array where we write 0 because I don't know how to use structs (list?) for now).
The numbers which stay are all prime numbers under the one you chose (rest? sorry for my bad English)
Thanks.

Answer 1

the following proposed code:
cleanly compiles
performs the desired functionality
is NOT efficient
shows proper indentation
shows meaningful variable names
properly passes the allocated memory to `free_ before exiting
properly checks for successful execution of scanf()
and now, the proposed code:
/*librairies*/
#include <stdio.h>
#include <stdlib.h>
/*main function*/
int main( void )
{
size_t targetNum;
size_t i; // index
size_t j; // index
size_t *primeArray = NULL; /*pointer which will become an array (see in another after comment)*/
printf("Enter Your target number : ");
if( scanf("%lu", &targetNum) != 1 )
{
fprintf( stderr, "scanf failed to read target number\n" );
exit( EXIT_FAILURE );
}
if ( targetNum > 1 )
{
primeArray = malloc( targetNum * sizeof( size_t ) );
if ( !primeArray )
{
perror( "malloc failed" );
exit( EXIT_FAILURE );
}
// initialize array of prime numbers
for ( i = 0; i < targetNum; i++ )
{
primeArray[i] = 1;
}
primeArray[0] = 0;
primeArray[1] = 0;
// find primes and zero multiples
for( i = 0; i < targetNum; i++ )
{
// skip any multiples of primes (which have already been zero'd
if( !primeArray[i] )
{
continue;
}
// zero multiples
for( j = i+i; j < targetNum; j+=i )
{
primeArray[j] = 0;
}
}
// print primes
for ( i = 0; i < targetNum; i++ )
{
if( primeArray[i] )
{
printf( "%lu\n", i );
}
}
free( primeArray );
}
else
{
printf("Your number is not valid\n");
}
return 0;
}
given the following input:
4
the output is:
Enter Your target number : 4
2
3