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~~Reasons to use the construct~~
~~> #define FOO(x) do{...} while(0);~~
~~(1) as mentioned above, solves the problem of~~
~~> if (...) FOO(y);~~
(2) you can to declare variables inside the block, and they harmlessly go out of scope at the end of the block. Without the do{} block, the same symbol would cause a warning (or worse) if it were declared elsewhere in the block in which FOO(x) gets expanded.
Why declare variables inside a macro? In case a macro argument appears more than once in the body, and someone writes FOO(func(y)), where func has side effects. This includes FOO(y++) etc. After the macro expands, the side effect would happen as many times as the macro argument appears in the body!
~~Declaring a variable inside a do {} block prevents this, as follows:~~
~~> #define FOO(x) do { long xx = x; func2(xx); func3(xx); } while (0);~~
~~Obviously there is still an assumption about type of x, but that is the case anyway if you are going to be calling func2(x) etc~~
(3) Without the do{} block, there might be ambiguity as to whether FOO(x) expands into a statement or an expression. do{} makes it clearly a statement, which can help catch someone trying to use FOO(x) where an expression is expected. See also: "statement-expressions", aka ({...}), which is a construct in case you want the block to be an expression rather than a statement.

Reasons to use the construct `#define FOO(x) do{...} while(0);`:
1. As mentioned above, doing so solves the problem of
```
if (...) FOO(y);
```
1. You can declare variables inside the block, and they harmlessly go out of scope at the end of the block. Without the `do{}` block, the same symbol would cause a warning (or worse) if it were declared elsewhere in the block in which `FOO(x)` gets expanded.
Why declare variables inside a macro? In case a macro argument appears more than once in the body, and someone writes `FOO(func(y))`, where `func` has side effects. This includes `FOO(y++)` etc. After the macro expands, the side effect would happen as many times as the macro argument appears in the body!
Declaring a variable inside a do {} block prevents this, as follows:
```
#define FOO(x) do { long xx = x; func2(xx); func3(xx); } while (0);
```
Obviously there is still an assumption about type of `x`, but that is the case anyway if you are going to be calling `func2(x)` etc.
1. Without the `do{}` block, there might be ambiguity as to whether `FOO(x)` expands into a statement or an expression. `do{}` makes it clearly a statement, which can help catch someone trying to use `FOO(x)` where an expression is expected. See also: "statement-expressions", aka `({...})`, which is a construct in case you want the block to be an expression rather than a statement.

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