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 as well as a mechanism to update the information about codepoints permitted in
4 identifiers, which is encoded in libcpp/ucnid.h, and mapping between Unicode
5 names and codepoints, which is encoded in libcpp/uname2c.h.
7 The idea is to produce the necessary lookup tables
8 (../../libcpp/{ucnid.h,uname2c.h,generated_cpp_wcwidth.h}) in a reproducible
9 way, starting from the following files that are distributed by the Unicode
12 ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
13 ftp://ftp.unicode.org/Public/UNIDATA/EastAsianWidth.txt
14 ftp://ftp.unicode.org/Public/UNIDATA/PropList.txt
15 ftp://ftp.unicode.org/Public/UNIDATA/DerivedNormalizationProps.txt
16 ftp://ftp.unicode.org/Public/UNIDATA/DerivedCoreProperties.txt
17 ftp://ftp.unicode.org/Public/UNIDATA/NameAliases.txt
19 Two additional files are needed for lookup tables in libstdc++:
21 ftp://ftp.unicode.org/Public/UNIDATA/auxiliary/GraphemeBreakProperty.txt
22 ftp://ftp.unicode.org/Public/UNIDATA/emoji/emoji-data.txt
24 All these files have been added to source control in this directory;
25 please see unicode-license.txt for the relevant copyright information.
27 In order to keep in sync with glibc's wcwidth as much as possible, it is
28 desirable for the logic that processes the Unicode data to be the same as
29 glibc's. To that end, we also put in this directory, in the from_glibc/
30 directory, the glibc python code that implements their logic. This code was
31 copied verbatim from glibc, and it can be updated at any time from the glibc
32 source code repository. The files copied from that repository are:
34 localedata/unicode-gen/unicode_utils.py
35 localedata/unicode-gen/utf8_gen.py
37 And the most recent versions added to GCC are from glibc git commit:
38 71de3aead9fffe89556e80ebc94aa918d8ee7bca
40 The script gen_wcwidth.py found here contains the GCC-specific code to
41 map glibc's output to the lookup tables we require. This script should not need
42 to change, unless there are structural changes to the Unicode data files or to
43 the glibc code. Similarly, makeucnid.cc in ../../libcpp contains the logic to
46 The procedure to update GCC's Unicode support is the following:
48 1. Update the six Unicode data files from the above URLs.
50 2. Update the two glibc files in from_glibc/ from glibc's git. Update
51 the commit number above in this README.
53 3. Run ./gen_wcwidth.py X.Y > ../../libcpp/generated_cpp_wcwidth.h
54 (where X.Y is the version of the Unicode standard corresponding to the
55 Unicode data files being used, most recently, 15.1.0).
57 4. Update Unicode Copyright years in libcpp/makeucnid.cc and in
58 libcpp/makeuname2c.cc up to the year in which the Unicode
59 standard has been released.
61 5. Compile makeucnid, e.g. with:
62 g++ -O2 ../../libcpp/makeucnid.cc -o ../../libcpp/makeucnid
64 6. Generate ucnid.h as follows:
65 ../../libcpp/makeucnid ../../libcpp/ucnid.tab UnicodeData.txt \
66 DerivedNormalizationProps.txt DerivedCoreProperties.txt \
67 > ../../libcpp/ucnid.h
69 7. Read the corresponding Unicode's standard and update correspondingly
70 generated_ranges table in libcpp/makeuname2c.cc (in Unicode 15 all
71 the needed information was in Table 4-8).
73 8. Compile makeuname2c, e.g. with:
74 g++ -O2 ../../libcpp/makeuname2c.cc -o ../../libcpp/makeuname2c
76 9: Generate uname2c.h as follows:
77 ../../libcpp/makeuname2c UnicodeData.txt NameAliases.txt \
78 > ../../libcpp/uname2c.h
80 See gen_libstdcxx_unicode_data.py for instructions on updating the lookup