On a Tuesday in 2021, Daniel P. Berrangé wrote:
One of the conventions we have had since the early days of libvirt is that every struct typedef, has a corresponding "Ptr" typedef too.
For example
typedef struct _virDomainDef virDomainDef; typedef virDomainDef *virDomainDefPtr;
Periodically someone has questioned what the purpose of these Ptr typedefs is, and we've not had an compelling answer, other than that's what we've always done.
There are a few things that make me question the status quo
- If we want a const pointer, we can't use
const virDomainDefPtr def
because that expands to "struct _virDomainDef * const", which is not what we need semantically. Instead we must write
const virDomainDef *def
It is not at all obvious why these two are different, but none the less they are, which is confusing to contributors
To me this a compelling reason to consider the "Ptr" typedefs a waste of time, if not actively harmful.
Please don't suggest adding virDomainDefConstPtr too !
- Writing 'virDomainDefPtr' is actually two characters more typing than 'virDomainDef *'.
IOW these "Ptr" typedefs aren't saving us time when writing code.
Optimizing for reading speed is more important. So one more reason to get rid of this "obfuscation". But even for writing, I've had trouble getting coccinelle to understand some 'Ptr's, so I had to resort to slower alternatives. Jano