SIGABRT error, C (gcc)

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//Title of this code
#include <stdbool.h>
#include  <stdio.h>
#include <ctype.h>
int main(void)
{
    //int i;
    //char arrstr[10] = {'2','b','5','3','f','j','5','f','\0'}; 
    //for(i=0;arrstr[i]!='\0';i++)
      //  printf("%c is a digit: %s\n",arrstr[i],isdigit(arrstr[i])? "true" : "false");   
    //char *ptr = "5ellp";
    //bool x = isdigit(*ptr);
    //printf("%d",x);//t is a digit
    //char * ptr = "water runs dry"
      //  ;
    //printf("%s\n",ptr);
    //ptr="";
    //printf("%s",ptr);//segfault
    
    int i,j;
    
    char ** instrfields;
    
    instrfields = (char **)malloc(100*sizeof(char *));        
    
    for(i=0;i<3;i++){
        *(instrfields+i) = (char *)malloc(20*sizeof(char *));}
    
    char * ch1;char * ch2; char * ch3;
    
    ch1="soul";
    ch2="sister";
    ch3="train";
    
    instrfields[0]=ch1;
    instrfields[1]=ch2;
    instrfields[2]=ch3;
    
    
    
    for(j=0;j<3;j++){
        free(instrfields[j]);
    } free(instrfields);
        
    
    return 0;
}

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Compilation time: 0.21 sec, absolute running time: 0.09 sec, cpu time: 0 sec, memory peak: 3 Mb, absolute service time: 0.46 sec