Pros and Cons of Different macro function / inline methods in C
- by Robert S. Barnes
According to the C FAQ, there are basically 3 practical methods for "inlining" code in C:
#define MACRO(arg1, arg2) do { \
/* declarations */ \
stmt1; \
stmt2; \
/* ... */ \
} while(0) /* (no trailing ; ) */
or
#define FUNC(arg1, arg2) (expr1, expr2, expr3)
To clarify this one, the arguments are used in the expressions, and the comma operator returns the value of the last expression.
or
using the inline declaration which is supported as an extension to gcc and in the c99 standard.
The do { ... } while (0) method is widely used in the Linux kernel, but I haven't encountered the other two methods very often if at all.
I'm referring specifically to multi-statement "functions", not single statement ones like MAX or MIN.
What are the pros and cons of each method, and why would you choose one over the other in various situations?
