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Message-ID: <20230205234930.GM4163@brightrain.aerifal.cx>
Date: Sun, 5 Feb 2023 18:49:31 -0500
From: Rich Felker <dalias@...c.org>
To: Markus Wichmann <nullplan@....net>
Cc: musl@...ts.openwall.com, Peter Collingbourne <pcc@...gle.com>
Subject: Re: [PATCH] arm: Use __WCHAR_TYPE__ for wchar_t if defined
On Sun, Feb 05, 2023 at 09:00:03PM +0100, Markus Wichmann wrote:
> On Sat, Feb 04, 2023 at 08:08:36AM +0100, alice wrote:
> > On Sat Feb 4, 2023 at 7:30 AM CET, Peter Collingbourne wrote:
> > > When building with -fshort-wchar the definition of wchar_t is
> > > incorrect. Get the correct definition from the compiler if available.
> > >
> > > This is useful when reusing the freestanding parts of musl on a
> > > bare-metal target that uses -fshort-wchar.
> >
> > somebody talked about this in 2015, see
> > https://www.openwall.com/lists/musl/2015/02/18/2
> > for the previous discussion.
> >
> > i understand in this case it's proposed a little different-
> > "reusing freestanding parts" as opposed to building a whole libc.so, but in
> > that case you could most likely patch this in when reusing it standalone only?
> >
> > it doesn't seem a good idea for it to be there, in general.
>
> Seconded. A lot of code in musl depends on wchar_t being able to hold
> the current maximum Unicode codepoint of 0x10FFFF at least, so the type
> must be at least 21 bits.
Absolutely. -fshort-wchar requests a different ABI that is
fundamentally incompatible with libc and with use of the libc headers,
and also fundamentally incompatible with Unicode and the requirements
of the C language (unless you only want to support the BMP) -- C does
not allow "multi-wchar_t characters".
If you're targeting freestanding environment not using libc, you
should use -nostdinc and provide headers suitable to your environment
instead of the libc ones. But really you should fix the offending code
not to use wchar_t for UTF-16, and not use -fshort-wchar. Modern C has
a char16_t type for this purpose.
Rich
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