...
This noncompliant code example contains multiple, unbound statements.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
/* * Swaps two values. * Requires tmp variable to be defined. */ #define SWAP(x, y) \ tmp = x; \ x = y; \ y = tmp |
...
This noncompliant code example inadequately bounds multiple statements.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
/*
* Swaps two values.
* Requires tmp variable to be defined.
*/
#define SWAP(x,y) { tmp = x; x = y; y = tmp; }
|
This macro fails to expand correctly in some case, such as the following example, which is meant to be an if statement with two branches:
...
| Code Block | ||||
|---|---|---|---|---|
| ||||
if (x > y) { /* Single-branch if-statement!!! */
tmp = x; /* The one and only branch consists */
x = y; /* of the block. */
y = tmp;
}
; /* emptyEmpty statement */
else /* ERROR!!! "parse error before else" */
do_something();
|
...
Wrapping the macro inside a do-while loop mitigates the problem.:
| Code Block | ||||
|---|---|---|---|---|
| ||||
/*
* Swaps two values.
* Requires tmp variable to be defined.
*/
#define SWAP(x, y) \
do { \
tmp = x; \
x = y; \
y = tmp; } \
while (0)
|
...