[phobos] Two questions about the use of libc in Phobos

[Andrei Alexandrescu]

On 04/07/2010 10:27 AM, Sean Kelly wrote:
> On Apr 7, 2010, at 2:35 AM, Lars Tandle Kyllingstad wrote:
>
>> This is mostly out of curiosity, but also relevant for any future
>> contributions to Phobos:
>>
>> 1. AFAIK, the full interface for the C standard library is in
>> druntime, specifically the core.stdc package, with OS-dependent
>> stuff in core.sys.  Yet, there still exists an std.c package in
>> Phobos that contains more or less the same things, and which is
>> used extensively throughout the rest of the library.  Is this
>> intentional, or am I just seeing the relics of pre-druntime
>> Phobos?
>
> A bit of both.  When std.c was moved it was easier to turn those into
> forwarding modules.  They remain mostly because some contain
> nonstandard declarations and I haven't spent much time working on
> core.sys, though perhaps the proper thing in the case of what's left
> in std.c is just to declare it privately inside the Phobos module
> that needs the routine.
>
>> 2. Phobos uses functions from the C standard library in favour of
>> native D implementations in several places.  (In light of recent
>> discussions, std.stdio.File comes quickly to mind.)  Is this just a
>> way of getting things up and running quickly, with the intention of
>> D-ifying things later, or is it considered a permanent solution?
>
> core.stdc is present as much for users who want to port C code to D
> as anything else.  But I do see use of standard C routines as an
> indicator of where gaps are in Phobos.  It's really there "just in
> case."

In principle there's nothing wrong with using C functions, but the main 
problem is that many of them have problems, and others are unpleasant to 
use with D. Examples:

- atoi() is very wrong because not only it doesn't handle errors, it 
prevents the caller from diagnosing them.

- Many (strtoul, printf, etc. etc.) use pointers and char*-based 
interfaces that are unpleasant and unsafe with D.

- Some (e.g gets, sprintf) are extremely dangerous by design and can't 
be made safe.

What remains is a small core of functions such as stat(), which we can 
use no problem.


Andrei