On Mon, Mar 10, 2025 at 10:03:37PM +0100, Marek Vasut wrote:
> On 3/10/25 12:17 PM, Quentin Schulz wrote:
> > Hi Marek,
>
> Hi,
>
> > On 3/8/25 9:12 PM, Marek Vasut wrote:
> > > Fix the following conversion overflow errors. The input field is already
> > > limited to 3/2/1 bits using the bitwise and, move the parenthesis around
> > > to avoid the bogus warning:
> > >
> > > "
> > > fs/exfat/utf.c: In function ‘utf8_to_wchar’:
> > > fs/exfat/utf.c:165:23: warning: overflow in conversion from ‘int’ to
> > > ‘wchar_t’ {aka ‘short unsigned int’} changes value from ‘(int)(short
> > > unsigned int)*input << 18 & 1835008’ to ‘0’ [-Woverflow]
> > > 165 | *wc = ((wchar_t) input[0] & 0x07) << 18;
> > > | ^
> > > fs/exfat/utf.c:170:23: warning: overflow in conversion from ‘int’ to
> > > ‘wchar_t’ {aka ‘short unsigned int’} changes value from ‘(int)(short
> > > unsigned int)*input << 24 & 50331648’ to ‘0’ [-Woverflow]
> > > 170 | *wc = ((wchar_t) input[0] & 0x03) << 24;
> > > | ^
> > > fs/exfat/utf.c:175:23: warning: overflow in conversion from ‘int’ to
> > > ‘wchar_t’ {aka ‘short unsigned int’} changes value from ‘(int)(short
> > > unsigned int)*input << 30 & 1073741824’ to ‘0’ [-Woverflow]
> > > 175 | *wc = ((wchar_t) input[0] & 0x01) << 30;
> > > | ^
> > > "
> > >
> >
> > Since this doesn't seem to be U-Boot-specific, any chance to open a Pull
> > Request on the project so we may be able to not carry this patch when
> > upgrading (yes, the last commit in the branch was two years ago, but it
> > seems the maintainer is still active on issues).
> >
> > Considering that wchar_t is an unsigned short int and that USHRT_MAX is
> > 0xffff (so 2B or 16b)...
> In fact, this error does not even appear in upstream , because upstream does
> not use -fshort-wchar compiler flag . U-Boot does use this compiler flags
> since 4a85663ec7ed ("kbuild: Enable -fshort-wchar") .
>
> So I wonder if this might be the right fix here instead:
>
> diff --git a/fs/exfat/Makefile b/fs/exfat/Makefile
> index 550c0683d65..8ca112cf0e9 100644
> --- a/fs/exfat/Makefile
> +++ b/fs/exfat/Makefile
> @@ -1,6 +1,9 @@
> # SPDX-License-Identifier: GPL-2.0+
> #
>
> +# The utf.o does really need 32bit wchar_t
> +CFLAGS_REMOVE_utf.o := -fshort-wchar
> +
> obj-$(CONFIG_FS_EXFAT) += \
> cluster.o \
> io.o \
Your initial approach is right I think, I'm not sure it's a good idea
to mix and match that flag throughout the codebase.
--
Tom
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