/in/ex1.c: In function 'main':
/in/ex1.c:11:15: error: conversion to 'char' from 'int' may alter its value [-Werror=conversion]
     while((ch=getchar()) && ch!='\n'){
               ^~~~~~~
/in/ex1.c:18:9: error: statement with no effect [-Werror=unused-value]
         *ch_extension[i]
         ^~~~~~~~~~~~~~~~
/in/ex1.c:19:5: error: expected ';' before '}' token
     }
     ^
/in/ex1.c:9:10: error: unused variable 'ch_max' [-Werror=unused-variable]
     char ch_max[21];
          ^~~~~~
cc1: all warnings being treated as errors