[Spiritus]

What's the deal with the `while ... while(0)` and `do ... while(0)` macros? Is it some scoping trick?

    #define TKVDB_EXEC(FUNC)           \
    do {                               \
        TKVDB_RES r = FUNC;            \
        if (r != TKVDB_OK) {           \
            return r;                  \
        }                              \
    } while (0)

    #define TKVDB_SKIP_RNODES(NODE)    \
    while (NODE->c.replaced_by) {      \
        NODE = NODE->c.replaced_by;    \
    } while (0)

[jwilk]

do … while(0) is a well-know method of writing multi-statement macros:

http://c-faq.com/cpp/multistmt.html

while … while(0) looks like a mistake?

[vmxdev]

Yes, the first macro is the common trick, and the second is the mistake (wondering, but it works). I update the code. Thanks a lot for pointing it out!

[zambal]

You are correct. At least the do... while statement is a common c macro trick to make sure a macro has its own scope. The idea is that a compiler will optimize the do....while statement away, so it does not have any runtime overhead.

The wile...while(0) statement is new for me (didn't know this is actually legal syntax), but I suspect it's done for similar reasons.

[jwilk]

> didn't know this is actually legal syntax

It looks like some unusual looping syntax; but in fact these are just two normal while loops one after another.