Re: [PATCH 0/6] Address issues with SPDX requirements and PEP-263

[Markus Heiser]

Am 07.09.19 um 20:04 schrieb Mauro Carvalho Chehab:
> Em Sat, 7 Sep 2019 19:33:06 +0200
> Markus Heiser <markus.heiser@xxxxxxxxxxx> escreveu:
> > An (uncatched) exception is thrown, when writing UTF-8 to a stream which
> > do not support UTF-8 .. this is not a crash, it mostly indicates that the
> > developper makes some wrong assumption about the use-case.
>
> A not-handled exception is a crash in Python. I've seen python scripts
> crash countless times with non-English names.

This has nothing to do with the language, ask the developer of those scripts.

> > There exists
> > also the possibility to encode the UTF-8 to ASCII and replace unknown
> > code points in the out-stream, or to catch the exception.
>
> Yeah, but getting this right is very painful. I use patchwork since 2013.
> It took *years* for it to not crash with non-ASCII chars[1]. That's, btw,
> the primary reason why I don't usually use python: with other languages,
> an alien char doesn't cause a crash.

Python cares encoded (text) string-types while other languages and
application are just piping bytes to streams .. if you care about the
enconding you need exceptions when one whants write UTF-8 to ASCII out.

Anyway this is a bit of nitpicking / not helping here ..

> [1] I might be wrong, but the last patch I saw addressing an issue
>      there was applied this year.

I alrady postet an example [1]

<snip>
This means your application has to know the encoding of a stream/file.
E.g. we handle the output from of the external Perl script
scripts/kernel-docs by encoding the byte stream from proc-call's
stdout into utf-8:

   out, err = codecs.decode(out, 'utf-8'), codecs.decode(err, 'utf-8')

see patch 
https://github.com/torvalds/linux/commit/86c0f046a8b0c23fca65f77333c233a06c25ef9a

Again, this is talking about application development and has
nothing to do with the encoding of the source files.
<snap>

[1] https://www.mail-archive.com/linux-doc@xxxxxxxxxxxxxxx/msg33240.html

> > But this was only academical, where do we have such problems in practice?
> >
> > > At least on media, we define that some Kernel strings can be UTF-8.
> > > See, for example the model field at the media_entity struct:
> > >
> > > 	https://linuxtv.org/downloads/v4l-dvb-apis/kapi/mc-core.html
> > >
> > > As stated there:
> > >
> > > 	"media_entity.model must be filled with the device model name as
> > > 	 a NUL-terminated UTF-8 string. The device/model revision must
> > > 	 not be stored in this field."
> > >
> > > I've no idea if the two perf scripts that contain the encoding data are
> > > meant to print some strings that may be UTF-8 encoding (like those that
> > > we have at the media subsystem), or if it is just that whomever added
> > > were using e-macs and wanted to make his life simpler. As it is better
> > > to be safe then sorry, on patches 2 and 3, I'm assuming the first case.
> >
> > Hm, I'am unsure if I understand you correct: Using UTF-8 in the .rst
> > files are fine .. where do we have scripts generating UTF-8 outputs?
> > (except the HTML output).
>
> In thesis, perf scripts may be reading strings from the Kernel, with
> might be using UTF-8 encoding.
>
> > > In any case, we do need the encoding line at Sphinx extensions,
> > > although there, the shebang line is optional.
> > >
> > > In other words, we have those alternatives:
> > >
> > > 1) Neither shebang nor coding -> SPDX will be at first line;
> > > 2) shebang + SPDX -> SPDX will be at the second line;
> > > 3) shebang + coding + SPDX -> SPDX will be at the third line;
> > > 4) coding + SPDX
> > >
> > >      This is something that only makes sense for Sphinx extensions.
> > >
> > >      IMHO, I would place SPDX at the second line too, but I *guess* Python
> > >      may accept it at the first line and would still properly evaluate
> > >      coding (as this technically satisfies the text at PEP-263).
> >
> > Why you are so restrictive ..
>
> No idea. I would actually prefer to just remove the restriction, and let
> the SPDX header to be anywhere inside the first comment block inside a
> file [2].
>
> That's basically how this thread started: other developers think
> that it is a good idea to be pedantic. So, be it, but let's then fix
> the documentation, as the way it is, it is implicitly forbidding the
> addition of encoding lines for Python scripts.
>
> [2] I *suspect* that the restriction was added in order to make
>      ./scripts/spdxcheck.py to run faster and to avoid false positives.
>      Right now, if the maximum limit is removed (or set to a very high
>      value), there will be one false positive:
>
> 	Documentation/dev-tools/kselftest.rst
>
>      This doc has a SPDX-like tag at line 230, asking people to add SPDX
>      headers on files, but the file itself doesn't have its own SPDX tag.
> 	
> > what we normal do:
> >
> > - write a shebang line if this file is called directly from the
> >     command line .. but we do not need shebangs on py modules which
> >     are imported from other modules or scripts
> >
> > - write a encoding line if it is need or helpful / mostly it is helpful
> >     to know the encoding of a text/code file.
> >
> > - add a SPDX tag
>
> Yes, but this violates the current documentation, as it doesn't allow the
> SPDX tag after line #2.

Thats what I mean: The documentation was written with only a small use-cases
in mind .. there is no real need for SPDX to be in line one or two ... lets
fix the documentation as I described before.

Side note: if I can help you with perf or your build systems, don't hesitate
to contact me directly.

-- Markus --

> > At the end we will have files with one, two or all three of this lines.
> > And the oder of this lines is, what I wrote:
> >
> > > > Thats what I mean [1] .. lets patch the description in the license-rules.rst::
> > > >
> > > > - first line for the OS (shebang)
> > > > - second line for environment (python-encoding, editor-mode, ...)
> > > > - third and more lines for application (SPDX use) ..
> > > >
> > > > [1] https://www.mail-archive.com/linux-doc@xxxxxxxxxxxxxxx/msg33240.html
> > > >
> > > > -- Markus --
> > > >   
> > > > > This suggests to me that we're adding a bunch of complications that we
> > > > > don't necessarily need.  What am I missing here?
> > > > >
> > > > > Educate me properly and I'll not try to stand in the way of all this...
> > > > >   
> >
> >
> > It seems like it is not only me who is mising something .. what are
> > the use-cases we have py-Exceptions, what are the use-cases to be so
> > restrictive as you described above.
> >
> > .. or did alice get lost in the cave?
> >
> > Thanks for your patience with me
> >
> > -- Markus --
>
>
>
> Thanks,
> Mauro