foo.cpp: In constructor 'bign::bign()':
foo.cpp:29:29: error: 'memset' was not declared in this scope
  bign(){memset(s,0,sizeof(s));len=1;}
                             ^
foo.cpp: In member function 'bign bign::operator=(const char*)':
foo.cpp:33:20: error: 'strlen' was not declared in this scope
   ol=len=strlen(num);
                    ^
foo.cpp:36:23: error: 'memset' was not declared in this scope
   memset(s,0,sizeof(s));
                       ^
foo.cpp: In member function 'bign bign::operator=(int)':
foo.cpp:44:21: error: 'sprintf' was not declared in this scope
   sprintf(s,"%d",num);
                     ^
foo.cpp: In function 'bign& operator++(bign&, int)':
foo.cpp:212:7: warning: reference to local variable 't' returned [-Wreturn-local-addr]
  bign t=a;
       ^
foo.cpp: In function 'bign& operator--(bign&, int)':
foo.cpp:223:7: warning: reference to local variable 't' returned [-Wreturn-local-addr]
  bign t=a;
       ^