Re: [Plplot-devel] CMake problem with hyphen in path

[Alan W. I. <Ala...@gm...>]

On 2019-07-13 08:05-0000 Phil Rosenberg wrote:

> Hi Alan
> You may be right.
> I tried commenting out the offending regex replace, which meant cmake finished with no issues. But, when I tried to compile I found I had a similar problem with header files. I couldn't actually find the offending code that is causing that problem. I tried adding some quotes, but that didn't seem to help.
>
> So whatever workload you thought it was, it is actually double!

Actually there is at least one or two orders of magnitude more work
according to my Linux tests if you consider dealing with this problem
for all external free software libraries that PLplot depends on rather
than just wxwidgets.  And the results would depend on all external
libraries (and CMake itself) dealing with blank in pathname issues
correctly which some preliminary tests I have done appears to be far
from the case.  So the fundamental issue is PLplot has been
responsible about its own internal source, build, and install tree
blanks in pathname issues, but other free software has not been that
responsible.  And a large supplementary issue is that even if external
software eventually becomes completely responsible about this case,
there would still be a lot more to do on the PLplot side to make
"space in external library prefix" case work properly for all external
libraries.

> Would it be relatively straightforward to add a check, so if the user supplies an install or library/header path that contains " -" then we error out at that point?

The problem with *complete* configuration-time detection of that case
is that we would have to have reliable parsing to detect the
difference between hyphenated/spaced pathnames as opposed to the " -"
that delimits linker options.  That said, we could easily warn against
the case where "- " appears anywhere in the options string since that
case is obviously not a linker option.  If you agree, I will take
responsibility for implementing such a check.

But that check would obviously not guard against the case of, say, an
-L option of the form

-L/whatever -hyphen_pathname

where "whatever -hyphen_pathname" was the complete pathname rather
than "whatever" being the pathname with "-hyphen_pathname" being a
separate linker option.  And the check would only be available for
the external wxwidgets library and all external libraries that
use pkg-config.

So to supplement that proposed incomplete configuration-time check I
think we should create a prominent warning in our wiki for users not
to use installation prefixes that contain spaces for external free
software libraries.  I emphasize spaces rather than hyphens here since
it is the spaces that generate all the issues with or without hyphens
according to my Linux tests.  Also, most experienced Unix users would
not try spaces in installed library prefixes, but some might do that
so I think the warning should be a general one rather than Windows
only.

If you agree that wiki "no-space in external library prefixes" warning
would be useful as well, would you take responsibility for updating
the most fundamental PLplot build page in our wiki (whatever that is)
to that effect?

Alan
__________________________
Alan W. Irwin

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.org); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
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Linux-powered Science
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