In file included from main.cpp:17:0:
factory.h: In function 'Object* my_new_smth_()':
factory.h:56:21: error: 'class_id' was not declared in this scope
     return new Smth(class_id);
                     ^~~~~~~~
factory.h:56:21: note: suggested alternative: 'class'
     return new Smth(class_id);
                     ^~~~~~~~
                     class
main.cpp: At global scope:
main.cpp:27:7: error: redefinition of 'class Smth'
 class Smth : public Object {
       ^~~~
In file included from main.cpp:17:0:
factory.h:41:7: note: previous definition of 'class Smth'
 class Smth : public Object {
       ^~~~
main.cpp: In function 'Object* my_new_smth_()':
main.cpp:40:9: error: redefinition of 'Object* my_new_smth_()'
 Object* my_new_smth_() {
         ^~~~~~~~~~~~
In file included from main.cpp:17:0:
factory.h:55:9: note: 'Object* my_new_smth_()' previously defined here
 Object *my_new_smth_() {
         ^~~~~~~~~~~~