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1 This directory contains a mechanism for GCC to have its own internal
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2 implementation of wcwidth functionality. (cpp_wcwidth () in libcpp/charset.c).
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3
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4 The idea is to produce the necessary lookup table
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5 (../../libcpp/generated_cpp_wcwidth.h) in a reproducible way, starting from the
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6 following files that are distributed by the Unicode Consortium:
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7
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8 ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
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9 ftp://ftp.unicode.org/Public/UNIDATA/EastAsianWidth.txt
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10 ftp://ftp.unicode.org/Public/UNIDATA/PropList.txt
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11
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12 These three files have been added to source control in this directory;
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13 please see unicode-license.txt for the relevant copyright information.
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14
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15 In order to keep in sync with glibc's wcwidth as much as possible, it is
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16 desirable for the logic that processes the Unicode data to be the same as
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17 glibc's. To that end, we also put in this directory, in the from_glibc/
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18 directory, the glibc python code that implements their logic. This code was
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19 copied verbatim from glibc, and it can be updated at any time from the glibc
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20 source code repository. The files copied from that respository are:
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21
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22 localedata/unicode-gen/unicode_utils.py
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23 localedata/unicode-gen/utf8_gen.py
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24
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25 And the most recent versions added to GCC are from glibc git commit:
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26 2a764c6ee848dfe92cb2921ed3b14085f15d9e79
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27
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28 Finally, the script gen_wcwidth.py found here contains the GCC-specific code to
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29 map glibc's output to the lookup tables we require. This script should not need
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30 to change, unless there are structural changes to the Unicode data files or to
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31 the glibc code.
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32
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33 The procedure to update GCC's wcwidth tables is the following:
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34
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35 1. Update the three Unicode data files from the above URLs.
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36
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37 2. Update the two glibc files in from_glibc/ from glibc's git. Update
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38 the commit number above in this README.
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39
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40 3. Run ./gen_wcwidth.py X.Y > ../../libcpp/generated_cpp_wcwidth.h
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41 (where X.Y is the version of the Unicode standard corresponding to the
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42 Unicode data files being used, most recently, 12.1).
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43
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44 After that, GCC's wcwidth will match the most recent glibc.
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