Re: [Libguestfs] [libnbd PATCH v4 1/3] lib/utils: introduce xwritel() as a more robust and convenient write()

On 3/15/23 15:01, Eric Blake wrote: Thanks for the thorough review; I'm glad all the fine points I sought to put in the patch were received -- and well-received! :) One question: Do we have general rules on attribute usage in libnbd vs. nbdkit? The __sentinel__ (aka sentinel) attribute is used in nbdkit, but not yet in libnbd. Now, that could be happenstance, but it rhymes with another (obscure?) discrepancy in attribute usage. Namely, when I was comparing the common/ subdirectories of both projects, I noticed that nbdkit used the cleanup attribute, and libnbd didn't. First I thought it was a mistake / oversight, but then I found a porting note from Rich, in libnbd commit f306e231d294 ("common/utils: Add extensible string, based on vector", 2022-03-12): RWMJ: This removes the CLEANUP_FREE_STRING macro since libnbd does not use __attribute__((cleanup)). and then again in f3828bfd42be ("common/utils: Add new string vector types", 2022-03-12): RWMJ: Removed the CLEANUP_* macros. So those comments (esp. the one on commit f306e231d294) at least confirm that the difference is intentional. I still don't know the reason for the difference. And now I wonder: does the same (unexplained) reason underlie the "sentinel" attribute's absence too, in libnbd? If there is a common reason for avoiding both "cleanup" and "sentinel" in libnbd, we should probably not start using "sentinel" now. If, on the other hand, "sentinel" is not covered by the same argument as "cleanup" (not to mention if there isn't an actual reason for avoiding "cleanup" in the first place!), then I can add the sentinel attribute when merging this patch. Thanks! Laszlo