Groups | Search | Server Info | Login | Register

Groups > muc.lists.netbsd.tech.misc > #112

Re: alx-0008 - Standardize strtoi(3) and strtou(3) from NetBSD

Show all headers | View raw

On 2025-03-19 18:15, Alejandro Colomar wrote:

> I think that you'd
> benefit from range checks, actually.  (See my response to his email.)
> <https://lore.kernel.org/liba2i/6oyljvsenypqnrmgjbcwskqpdsag677h2dzay6hvfoosju4224@3j7iczm4d7nw/T/#m38066e6eec63a8906e3cbfea275c9d7940d8df98>

That's a long email and I'm not sure I'm looking at the right place in 
it, but if I understand correctly it says that Gnulib code like this:

   port = strtoul (servname, &c, 10);
   if (port > 0xffff)
     return EAI_NONAME;

would be clearer if worded this way:

   port = strtou (servname, &c, 10, 0, 0xffff, &err);
   if (err == ERANGE)
     return EAI_NONAME;

If so, I disagree. The strtou API is more complicated, and the reader is 
likely to forget what each of its arguments means, e.g., that the 0 is a 
minimum and the 0xffff is a maximum. The strtoul API is simpler and it's 
more obvious what is intended.


> Do you mean that the implementation of strspn(3) was temporarily broken?
> Or that the specification is bad?

No, strspn itself is fine. It's that call to strspn that is broken. The 
call assumes that only ' ', '\t', and '\n' satisfy c_isspace, which is 
incorrect. This is an area where c_isspace is simpler and easier to 
follow than strspn.


>> For this particular resource, a limit of ULONG_MAX has the same practical
>> effect as a limit of ULONG_MAX + 1. Since the user can't tell the difference
>> in behavior, it's fine to implement the larger limit as the smaller one,
>> with no diagnostic.
> 
> According to Bruno, that limit is later clamped at a much lower value,
> so I think that clamping could be moved up to the strtou(3) call.

Yes, it could be moved into strtou, but there's a cost in simplicity and 
easy of understanding.


> How do you get a uintmax_t?

With a different function a2u that comes with a different struct (just 
like strtoi/strtou).

> Also, how do I perform range checks in that call?  I need to specify
> min and max limits.

The caller should do the range checks, as this makes C code easier to 
follow, both by the human programmer and the compiler, which can more 
easily use the range information to generate better code.

For cases like these having a function do the range checks is often a 
mistake - it doesn't significantly increase reliability (on the 
contrary, it can reduce it). But if you prefer a function with range 
checks, it's easy to add bounds arguments.

> How do you know how much has been parsed on error?

Good point. I guess we'll need three elements to the structure, then.

At this point we're bikeshedding but you can have the last word if you like.


--
Posted automagically by a mail2news gateway at muc.de e.V.
Please direct questions, flames, donations, etc. to news-admin@muc.de

Back to muc.lists.netbsd.tech.misc | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Re: alx-0008 - Standardize strtoi(3) and strtou(3) from NetBSD Alejandro Colomar <alx@kernel.org> - 2025-03-20 02:15 +0100
  Re: alx-0008 - Standardize strtoi(3) and strtou(3) from NetBSD Paul Eggert <eggert@cs.ucla.edu> - 2025-03-20 00:03 -0700
    Re: alx-0008 - Standardize strtoi(3) and strtou(3) from NetBSD Alejandro Colomar <alx@kernel.org> - 2025-03-20 11:32 +0100

csiph-web