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

[Laszlo Ersek]

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.

Just my two cents, since I've been CC'd.

Laszlo