foo.cc: In function 'bool pre_works()':
foo.cc:58:23: warning: array subscript has type 'char' [-Wchar-subscripts]
   58 |                 coded[--len_code]='\0' ;
      |                       ^~~~~~~~~~
foo.cc: In function 'bool check_code(char*, int)':
foo.cc:109:48: 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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