foo.cc: In function 'bool pre_works()':
foo.cc:58:15: warning: array subscript has type 'char' [-Wchar-subscripts]
   58 |         coded[--len_code]='\0' ;
      |               ^~~~~~~~~~
foo.cc: In function 'bool check_code(char*, int)':
foo.cc:109:44: warning: unused variable 'tmp' [-Wunused-variable]
  109 |     for( char *pc=cur_code, *pre=cur_code, tmp=0; pc!=cur_code+cur_len+1; pc++ ){
      |                                            ^~~

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