Re: [musl] [BUG] hasmntopt weirdness

[Rich Felker <dalias@libc.org>]

On Thu, Mar 30, 2023 at 10:47:27PM +0800, Matthias Görgens wrote:
> On Thu, 30 Mar 2023 at 21:57, Rich Felker <dalias@libc.org> wrote:
> > I'm pretty sure it was agreed upon at one point that this was a bug,
> > but never pursued further.
> 
> OK, that's good to know!
> 
> > From what I remember, I think hasmntopt needs to check that the match
> > found is at the start or immediately follows a comma (unless there is
> > some awful way to embed literal commas) and that it's followed by an
> > equals sign, comma, or nul terminator. Does this sound correct?
> 
> For what it's worth, that's close to what glibc does.
> 
> Sorry, I'm new to this: Is there a spec to these things, or do we just copy what
> the other C standard libraries are doing?

For standard functions, there is a spec.

For nonstandard ones, generally no, and that's why musl frowns on
them. We have to basically do what the standardization process would
have done: looking at historical practice and whether the interface
and behavior was sufficiently consistent across different historical
systems with the nonstandard extension that we can work out a behavior
that's not conflicting with what applications might expect.

When this is difficult or impossible, that's a strong indication that
we shouldn't adopt the interface at all. But due to historical
mistakes (not doing sufficient analysis to apply these principles), we
let a few things in we shouldn't have.