2019q1 Homework1 (list)

contributed by < TsundereChen >

tags: sysprog TsundereChen

• GitHub Repo

Note

Function-like macro

• Function-like macro definition
  • An identifier followed by a parameter list in parentheses and the replacement tokens
  • Parameters are imbedded in the replacement code
  • White space can't separate the identifier
  • A comma must separate each parameter
  • For portability, shouldn't have more than 31 parameters in a macro
  • __VA_ARGS__ may appear in the replacement list
• Function-like macro invocation
  • An identifier followed by a comma-separated list of args in parentheses
  • Number of args should match the number of params in the macro definition, unless parameter list in the definition ends with an ellipsis
  • If parameter list ends with an ellipsis, the number of args in the invocation should exceed the number of params in the definition
  • Preprocessor handles argument substitution
  • __VA_ARGS__ is replaced by trailing args if permitted by the macro definition
• Example
  ​​#define SUM(a, b) (a + b)
  ​​c = SUM(x, y); /* c = (x + y); */
  ​​c = d * SUM(x, y); /* c = d * (x + y) */
  ​​
  ​​#define SQR(c) ((c) * (c))
  ​​y = SQR(a + b); /* y = SQR((a + b) * (a + b)); */
  ​​
  ​​#define debug(...) fprintf(stderr, __VA_ARGS__)
  ​​debug("foo"); /* fprintf(stderr, "foo") */
  

static inline versus function-like macro

• static inline should be as quick as function-like macro
  • Since both of them replace the original code

typeof

• typeof can be used with experssion or type
  • Experssion
    typeof(x[0](1))
  • Type
    typeof(int *)

TODO

• Complete Homework requirement

Reference

• Macro vs Function in C - StackOverflow
• Inline Functions in C
• Function-like macros - IBM Knowledge Center