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      1 This directory contains a mechanism for GCC to have its own internal
      2 implementation of wcwidth functionality.  (cpp_wcwidth () in libcpp/charset.c).
      3 
      4 The idea is to produce the necessary lookup table
      5 (../../libcpp/generated_cpp_wcwidth.h) in a reproducible way, starting from the
      6 following files that are distributed by the Unicode Consortium:
      7 
      8 ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
      9 ftp://ftp.unicode.org/Public/UNIDATA/EastAsianWidth.txt
     10 ftp://ftp.unicode.org/Public/UNIDATA/PropList.txt
     11 
     12 These three files have been added to source control in this directory;
     13 please see unicode-license.txt for the relevant copyright information.
     14 
     15 In order to keep in sync with glibc's wcwidth as much as possible, it is
     16 desirable for the logic that processes the Unicode data to be the same as
     17 glibc's.  To that end, we also put in this directory, in the from_glibc/
     18 directory, the glibc python code that implements their logic.  This code was
     19 copied verbatim from glibc, and it can be updated at any time from the glibc
     20 source code repository.  The files copied from that respository are:
     21 
     22 localedata/unicode-gen/unicode_utils.py
     23 localedata/unicode-gen/utf8_gen.py
     24 
     25 And the most recent versions added to GCC are from glibc git commit:
     26 f6032247061fb37d59565f2e9667e242c8a98e76
     27 
     28 Finally, the script gen_wcwidth.py found here contains the GCC-specific code to
     29 map glibc's output to the lookup tables we require.  This script should not need
     30 to change, unless there are structural changes to the Unicode data files or to
     31 the glibc code.
     32 
     33 The procedure to update GCC's wcwidth tables is the following:
     34 
     35 1.  Update the three Unicode data files from the above URLs.
     36 
     37 2.  Update the two glibc files in from_glibc/ from glibc's git.  Update
     38     the commit number above in this README.
     39 
     40 3.  Run ./gen_wcwidth.py X.Y > ../../libcpp/generated_cpp_wcwidth.h
     41     (where X.Y is the version of the Unicode standard corresponding to the
     42     Unicode data files being used, most recently, 13.0.0).
     43 
     44 After that, GCC's wcwidth will match the most recent glibc.
     45