Object-oriented design patterns in the kernel, part 1

For this reason:
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void somefunction() {
do_something();
if (do_something_else())
return; //Whoopsie!
important_cleanup_code();
}
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In good C++ one would write something like:
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void somefunction() {
ON_SCOPE_EXIT(&important_cleanup_code);

do_something();
if (do_something_else())
return; //No whoopses.
do_something_really_else();
}
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If you use smart pointers it's even nicer:
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void shared_ptr<File> somefunction() {
const std::string &name=compute_file_name();
if (some_condition(name))
return shared_ptr(new File(name, FOR_READ));
if (anotherCondition())
throw my_exception(F("Something bad happened with the file ")<<name);
return shared_ptr(new File(name, FOR_WRITE));
}

//Call site
shared_ptr<File> fl=somefunction(); //that's it!
//One can even do
somefunction(); //For side effects, for example - returned file won't be lost
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In pure C you'll have to do something like:
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void int somefunction(file_object_ptr *result_place)
{
some_string name;
int res;
name=compute_file_name();

if (some_condition(name))
{
//And pray that your numeric error codes do not collide.
res=file_open_file(name, FOR_READ, result_place);
//What if we want to pass a verbose message
//like 'file <NAME> is locked by another process'?
goto cleanup;
}
if (anotherCondition())
{
res=E_SOMETHINGBAD;
//Verbose errors? Forget about it.
goto cleanup;
}

res=file_open_file(name, FOR_WRITE, result_place);

cleanup:
free_string(name);

return res;
}

//Call site
file_object_ptr obj=0; //Don't forget to initialize!
int res=somefunction(&obj);
if (res<0) return res; //Hope...
cleanup:
delete_file(obj);
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