在c中良好的宏观实践

Question

what is the better way to use macro and why 1)

CHECK(foo());
#define CHECK(foo) do{                            \
                           UCHAR status = foo;    \
                           if(0 != status)        \
                              // do some stuff    \
                              return status;      \
                        }while(0)

or 2)

UCHAR status = foo();
CHECK(status);

#define CHECK(status) do{                            \
                           if(0 != status)        \
                              // do some stuff    \
                              return status;      \
                        }while(0)

edited

thank You for all of You guys, a lot of people say that it is not good to use such piece of the code, but I have a lot of such pieces in my code (which I didn't write, only modify), what can You suggest?

Answer 1

I'd say the first one, since it takes care of avoiding multiple evaluation of foo , and who uses it doesn't need to remember to create the extra variable.

Still, personally I don't like macros that alter the execution flow like that, a programmer first seeing the codebase can easily miss a return point of the function.

Answer 2

Option 1 is easier to use since there is no need for the caller to worry about multiple evaluations of foo() . Option 1 also keeps the scope of the status variable as small as possible. Option 2 leaks the status variable into the scope of the caller.

Option 3 which doesn't use a macro at all is even better!