/in/fileReverse.c: In function 'reverse':
/in/fileReverse.c:14:12: error: conversion to 'int' from 'size_t {aka long unsigned int}' may alter its value [-Werror=conversion]
     len  = strlen(str);
            ^~~~~~
/in/fileReverse.c: In function 'main':
/in/fileReverse.c:28:21: error: 'len_num' undeclared (first use in this function)
     for(int i = 0;i<len_num;i++)
                     ^~~~~~~
/in/fileReverse.c:28:21: note: each undeclared identifier is reported only once for each function it appears in
cc1: all warnings being treated as errors