fixed ONLY the compilation (still crashes) for gcc 11.2.0 under Ubnutu 21.10 https://filetransfer.io/data-package/Xp1NUg99#link (that should still build/run on your debian 3)

there is a string struct with this inner char s is super-evil

in kernel.h

    /\* all strings on the stack will have this format. */
    typedef struct {
     unsigned int l; /* length of string */
     char s;  /* string itself \*/ 
            // the rest of the string data
    } string;

string get allocated by malloc(sizeof(string)+stringlen+1) and member char s is then used as the first char + the rest chars from the attached memory

the memory managment is overall a little dirty and i think it will take some time for a experienced C developer to get that clean and running with todays compiler/checks etc.