Re: [Qemu-devel] [PATCH] configure: Define NCURSES_WIDECHAR if we're using curses

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Jun 07, 2021 at 02:57:41PM +0200, Laszlo Ersek wrote:
> On 06/06/21 20:13, Stefan Weil wrote:
> > Am 02.06.17 um 16:35 schrieb Peter Maydell:
> > 
> >> We want the wide character functions from the ncurses header.
> >> Unfortunately it doesn't provide them by default, but only
> >> if either:
> >>   * NCURSES_WIDECHAR is defined (for ncurses 20111030 and up)
> >>   * _XOPEN_SOURCE/_XOPEN_SOURCE_EXTENDED are suitably defined
> >>
> >> So far we have been implicitly relying on the latter, because
> >> for GNU libc when we define _GNU_SOURCE this causes libc
> >> to define the _XOPEN_SOURCE macros for us. Unfortunately
> >> this doesn't work on all libcs, because some (like OSX and
> >> musl libc) do not define _XOPEN_SOURCE when _GNU_SOURCE
> >> is defined.
> >>
> >> We can't fix this by defining _XOPEN_SOURCE ourselves, because
> >> that also means "and don't provide any functions that aren't in
> >> that standard", and not all libcs provide any way to override
> >> that to also get the non-standard functions. In particular
> >> FreeBSD has no such mechanism, and OSX's _DARWIN_C_SOURCE
> >> doesn't reenable everything (for instance getpagesize()
> >> is still not prototyped if _DARWIN_C_SOURCE and _XOPEN_SOURCE
> >> are both defined).
> >>
> >> So we have to define NCURSES_WIDECHAR. (This will only work
> >> if your ncurses is at least 20111030, as older versions
> >> don't honour this macro.)
> > 
> > 
> > I answer to this very old e-mail because I noticed today that defining
> > NCURSES_WIDECHAR does not work with the latest MacOS on M1:
> > 
> > Apple still delivers a curses.h which indicates NCURSES_VERSION "5.7"
> > (20081102). It does not know NCURSES_WIDECHAR, but support for curses
> > can be enabled with _XOPEN_SOURCE_EXTENDED=1.
> > 
> > I used this patch for git master:
> > 
> > diff --git a/meson.build b/meson.build
> > index 626cf932c1..513332a76d 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -606,7 +606,7 @@ if have_system and not get_option('curses').disabled()
> >      endif
> >    endforeach
> >    msg = get_option('curses').enabled() ? 'curses library not found' : ''
> > -  curses_compile_args = ['-DNCURSES_WIDECHAR']
> > +  curses_compile_args = ['-DNCURSES_WIDECHAR',
> > '-D_XOPEN_SOURCE_EXTENDED=1']
> >    if curses.found()
> >      if cc.links(curses_test, args: curses_compile_args, dependencies:
> > [curses])
> >        curses = declare_dependency(compile_args: curses_compile_args,
> > dependencies: [curses])
> > 
> > 
> > Then curses is detected and works when configure is given the right
> > PKG_CONFIG_PATH:
> > 
> > PKG_CONFIG_PATH=/opt/homebrew/Library/Homebrew/os/mac/pkgconfig/11
> > ./configure
> 
> _XOPEN_SOURCE_EXTENDED is only supposed to make a difference in SUSv2.
> If MacOS needs it, whatever, but I don't view it as a good idea for any
> other host OS.

Easy to do with

  if host_machine.system() == 'darwin'
    curses_compile_args = [ '-D_XOPEN_SOURCE_EXTENDED=1']
  else
    curses_compile_args = ['-DNCURSES_WIDECHAR']
  endif

Regards,
Daniel
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