Re: Warning: "/usr/include/ncursesw" is unsafe for cross-compilation

[Joakim Tjernlund]

Thomas Dickey <address@hidden> wrote on 2014/09/14 16:22:55:

> 
> On Sun, Sep 14, 2014 at 03:57:04PM +0200, Joakim Tjernlund wrote:
> > Thomas Dickey <address@hidden> wrote on 2014/09/13 23:52:52:
> > > 
> > > On Fri, Sep 12, 2014 at 09:52:10AM +0200, Joakim Tjernlund wrote:
> > > > In Gentoo[1] one can see this warning when cross building ncurses 
with 
> > 
> > > > unicode support:
> > > >   cc1: warning: include location "/usr/include/ncursesw" is unsafe 
for 
> > 
> > > > cross-compilation [-Wpoison-system-directories]
> > > > This is because ncurses adds -I\${includedir} to CPPFLAGS, simply 
removing 
> > > 
> > > Actually, the --includedir option is used to override the program's 
sense
> > > of where the essential system headers are - if they are not in the 
default
> > > location used by the compiler.
> > 
> > --includedir is where the include files should be INSTALLED, not where 
system headers are.
> > 
> > > 
> > > Setting the option to point to the default location - or as shown in 
the bug report,
> > > to a redundant location - is pointless.
> > 
> > not so, it is set to where Gentoo wants to have ncursesw headers to be 

> > installed.
> 
> That's a nice goal, but it doesn't correspond to the way most 
applications
> use subdirectories of includedir, and is a source of bug-reports.
> 
> Because ncurses can be installed on systems where it may/may not be the
> default "curses" library, it provides (since 1995 - 7 years before 
Gentoo
> started) a configure option for what Gentoo appears to be attempting:
> 
>     --disable-overwrite
>    If you are installing ncurses on a system which contains another
>    development version of curses, or which could be confused by the 
loader
>    for another version, we recommend that you leave out the link to
>    -lcurses.  The ncurses library is always available as -lncurses.
>    Disabling overwrite also causes the ncurses header files to be
>    installed into a subdirectory, e.g., /usr/local/include/ncurses,
>    rather than the include directory.  This makes it simpler to avoid
>    compile-time conflicts with other versions of curses.h

Gentoo does not use --disable-overwrite, it simply builds both
narrowc ncurses and widec ncurses and chooses to install widec headers
in /usr/include/ncursesw

> 
> > Using that to search for include files is just plain wrong. The first 
time 
> > you build ncurses there is no files there at all.
> 
> Building ncurses uses header files from the cross-compiler's 
compile-time
> system - that's what includedir is normally (outside Gentoo's niche) 
used
> for.

The compiler knows were to find its system headers already. 

--includedir is not Gentoo specific, it is autoconf which specifies 
includedir to
be an install path.

If someone needs to add some special include dir during build, he/she 
should just pass
CPPFLAGS=-I/x/y/.. on the command line

> 
> > > For cross-compiling, there are some valid issues with the sample 
scripts which I use
> > > for making packages.  However, there has been no feedback that I 
recall from any packager
> > > regarding those scripts, so I have not discussed those issues 
(they're simply to-do items
> > > on my list (>1500 items...).
> > 
> > Ouch, that is some list
> 
> yes (I'll never run out, since it continues to grow).
> 
> > > > this makes it build
> > > > without this warning.
> > > 
> > > sometimes.
> > 
> > hmm, if there is some cross build fallout from removing includedir 
from 
> > CPPFLAGS that would have
> > to be fixed some other way.
> 
> probably.  Packagers with unusual requirements tend to write 
sed-scripts.

Sure but this seems to be a general bug in ncurses and should be fixed 
upstream

> 
> In a quick check of the package-scripts which I wrote for Debian and 
Fedora,
> I don't see that I had to bend any rules.

well, just building for the host and not using --includedir will of course 
work.

> 
> > > 
> > > > [1] https://bugs.gentoo.org/show_bug.cgi?id=522586
> > > > 
> > > >    Jocke
> > > > 
> > > > PS.
> > > >     Why are there no proper releases of ncurses? I can just find a 
lot of patches
> > > 
> > > I intend doing a regular release when I'm done with the MinGW port.
> > > (Packagers can pick up the patches, of course - even Gentoo).
> > 
> > Sure, but trying to understand what each change do is much harder when 
you only got
> > a patch containing many different changes.
> > 
> > > 
> > > >     Is the a public repo somewhere?
> > > 
> > > Someone keeps a git repository, as noted here:
> > > 
> > >    
https://lists.gnu.org/archive/html/bug-ncurses/2010-07/msg00021.html
> > 
> > This collects you patch files into one coherent src tree, much better 
than 
> > loose patch files.
> > It is not a replacement for a repo where one can follow each logical 
> > change in a commit though.
> 
> sure - but unlike the finer-grained repo, what you get is what I've 
tested
> for various combinations.

You still get that, you just push all commits at the same time. The 
benefits for the
community to have an external repo are significant.

Also, you have done a significant amount of fixes since last release so a 
new release with
that would be very welcome.