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From: "fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug stdio/28943] New: printf field width specifier is inconsistent
 between %d and %f for multibyte output
Date: Fri, 04 Mar 2022 08:12:20 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28943

            Bug ID: 28943
           Summary: printf field width specifier is inconsistent between
                    %d and %f for multibyte output
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: fweimer at redhat dot com
  Target Milestone: ---

With the ' and I flags, numeric conversions can include non-ASCII multibyte
characters. Presently, field width is handled differently for %f and %d
conversions. In %f conversions, the width is based on the number of
digits/separators before output encoding (each has width 1), with %d, width=
 is
based on bytes.

POSIX.1-2017 says:

=E2=80=9C
An optional minimum field width.  If the converted value has fewer bytes th=
an
the field width, it shall be padded with <space> characters by default on t=
he
left; it shall be padded on the right if the left-adjustment flag ('-'),
described below, is given to the field width.
=E2=80=9D

Which suggests the %d behavior. (POSIX only specifies ', but not I.) But th=
is
makes printf inconsistent with wprintf. Counting bytes is also seems not ve=
ry
useful for the column adjustments of numbers, particularly combined with
localization. So I think glibc should adopt character counts, not byte coun=
ts.

This only applies to the numeric conversions; for (non-wide) strings, field
width should continue to be measured in bytes, not multibyte characters.

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