On 2022-11-23 06:16, Alejandro Colomar wrote:
On 11/23/22 13:52, Stefan Puiu wrote:
On Wed, Nov 23, 2022 at 1:39 AM Guillem Jover wrote:
On Thu, 2022-11-10 at 12:36:47 +0100, Alejandro Colomar wrote:
On 11/10/22 01:13, Andrew Clayton wrote:
While looking at which systems provide memmem(3) I have been able to
discern the following:
musl libc since v0.9.7
bionic since Android 9
FreeBSD since 6.0
OpenBSD since 5.4
NetBSD
macOS
Illumos
For macOS and Illumos I checked the memmem(3) man page on those systems.
For the rest there are links below to on-line man pages or commit logs.
+FreeBSD 6.0, OpenBSD 5.4, NetBSD, macOS & Illumos.
For the commit message, it's interesting to note macOS and Bionic, for
speleology purposes. However, I'm opposed to adding them to the page itself
because of the following:
- macOS is not free software. I refuse to reference nonfree software on
this project.
I understand where you are coming from,
:-)
and from a full system PoV,
it's very true that macOS is non-free. But the lower layers of its
stack are free software (at least according to the FSF and OSI), such
as its kernel (Darwin), or its libc (where memmem() is implemented):
https://opensource.apple.com/source/Libc/Libc-1439.40.11/
among others.
Hmmm. Fair enough.
Similar with Solaris and Illumos (but with the CDDL, MIT, BSD), AFAIUI.
- Android is not a real Unix system, in that you can't even program in C in
there, unless you're Google or have hacked your system. It's not friendly
to us programmers, so we don't need to be friendly to it. I don't want to
be cluttering the pages with information that is irrelevant to normal users.
I'm assuming bionic is being used in some of the Android free
alternatives too, but then I'm not sure how usable for programming those
are either. And, well musl libc is not a real Unix system you can program
against either. :)
The difference is only that bionic is not in use in useful systems (AFAIK). :)
So we have to do some decision here (and also about newlib, as reported by Brian).
In any case I also find it useful to have this kind of portability
information when deciding what to use in code.
And I must admit it's also useful to me (this all started because Andrew and I
had to use memmem(3) at a project where macOS compatibility is relevant --not
critical, but relevant--).
But can understand the
reluctance to include such references, at least if thought out as the
entire system. Perhaps thinking about these merely at their kernel or
libc level would make including information about some of them more
palatable, given that standalone they are free software? So perhaps
an option is to instead refer to their specific components, say
"bionic libc X.Y", "Apple Libc M.N.O" or similar.
Yep, that's more palatable :)
I think I'd accept a patch stating Apple Libc version for memmem(3).
Not sure if it's the job of Linux man-pages to document when other
OSes started supporting certain APIs. That info has to be maintained,
updated etc. People can always read the man pages of other systems,
right? Maybe it's worth only pointing out when an interface is
Linux-only, or the Linux implementation diverges significantly.
The good thing is that in most cases, it's either something in POSIX (for which
I gon't care at all if Apple Libc or another-weirdo-libc decide to not support
it), or it's a Linux-only function.
So, there are few functions or syscalls that are generally available but are not
in POSIX, and it might be interesting to document that they're effectively as
portable as anything POSIX. Maybe even POSIX editors read this and decide to
add it.
In those cases, we still need to decide what we care about or not.
Musl libc is definitely a first-class citizen these days in Linux distributions.
I would start documenting them in the project at large if someone from musl
provides patches (I discussed this some time ago, but can't remember with who).
Rich, if you would like to discuss about this, we can have some chat.
For musl and other libcs, I think the man pages already document some
instances where their behavior diverges from glibc.
As said, for musl, I'd document them officially, if there's anyone interested
enough to send patches.
For other libcs, we have to decide if they're important enough, and probably
decide on a case-by-case basis.
Michael tried to have some decent coverage of non-GNU/Linux systems, both in the
man-pages and in his TLPI book. It's a useful thing. So much that sometimes
you don't even need to read other systems' pages at all to know how portable is
a GNU/Linux function.
So, I'd like to get opinions on interest about documenting details about:
- newlib (I never heard about it before; is it a widespread thing? do you think
it's useful?)
- Apple Libc (I still don't like it, but I must admit that it's relevant, and
being open source, it's more palatable)
- bionic (does anyone know if that's useful at all for anyone at all?)
Newlib is a Sourceware supported project originally by Cygnus then RedHat;
- now licensed under BSD, based partially on some BSD sources;
- used mainly for embedded systems and OSes, including those supported by
processor, system, and GCC tool chain vendors, and by manufacturers in their
products, some of whom contribute back to the project;
- significant libre OS RTEMS, which itself supports many embedded targets, is
used with space qualified hardware on ESA and NASA Mars orbiter projects, and
replaced glibc in NaCl a decade ago;
- info and man pages are generated from function source embedded comments using
makedoc/DocBook.
See below and the relevant .org sites:
https://en.wikipedia.org/wiki/Newlib
- that page also provide links to summary info on other libc implementations;
https://en.wikipedia.org/wiki/RTEMS
Newlib is included in Phil Zimmerman's regular comparison of all major C math
library implementations single thru quad precision functions:
https://members.loria.fr/PZimmermann/papers/accuracy.pdf
which compares GNU MPFR (to which PZ contributes) results to those from GNU
libc, Intel, AMD LibM, Newlib, OpenLibm, Musl, Darwin, LLVM libc, CUDA, and ROCm
math libraries.
Newlib is also used by Sourceware supported libre kernel emulator project Cygwin
originally by Cygnus then RedHat;
- works like a Unix distro hosted on and fully interoperable (unlike WSL so far)
with Windows;
- originally aiming for POSIX and feasible Solaris, now Linux, compatibility;
- supports over 12k BSD, GNU, and other libre libraries and packages;
- on both 64 and, until recently, 32 bit systems;
- appears to be used by manufacturers and vendors to provide embedded
development on Windows;
- support native Windows cross-compiler, binutils platform, and code base for
parts of the Mingw/32/64, Msys/2, and Wine projects, and others like Git for
Windows.
Cygwin provides its own utility, emulation library, newlib libc plus all
packages' GNU info and man pages, man-pages-posix, and also man-pages(-linux)
packages under man-db.
Compatibility with everything above kernel syscalls and data structures for
porting packages is the project goal, so process fork/exec, multithreading, and
multiprocessor scheduling are all supported using standard interfaces.
--
Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer but when there is no more to cut
-- Antoine de Saint-Exupéry
