# 2019q1 Homework1 (list)
contributed by < `TsundereChen` >
###### tags: `sysprog` `TsundereChen`

* [GitHub Repo](https://github.com/TsundereChen/linux-list)

## 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](https://hackmd.io/s/S12jCWKHN#%E4%BD%9C%E6%A5%AD%E8%A6%81%E6%B1%82)

## Reference
* [Macro vs Function in C - StackOverflow](https://stackoverflow.com/questions/9104568/macro-vs-function-in-c)
* [Inline Functions in C](http://www.greenend.org.uk/rjk/tech/inline.html)
* [Function-like macros - IBM Knowledge Center](https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_71/rzarg/cpxmac.htm)