https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95953
Bug ID: 95953 Summary: UTF Convert for UTF_16 to UTF_8 fails for values in U+10000 to U+10FFFF. Product: gcc Version: 7.3.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: ada Assignee: unassigned at gcc dot gnu.org Reporter: trashgod at gmail dot com Target Milestone: --- Created attachment 48798 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48798&action=edit complete example that reproduces problem and tests fix The library function Ada.Strings.UTF_Encoding.Conversions.Convert for UTF_16 to UTF_8 fails for values in the range U+10000 to U+10FFFF. Byte three of the four byte value is malformed; yyyyyyyy only needs to be shifted _two_ places left: Result (Len + 3) := Character'Val (2#10_000000# or Shift_Left (yyyyyyyy and 2#1111#, 2) -- originally 4 or Shift_Right (xxxxxxxx, 6)); A complete example, utftest.adb, is attached and discussed here: https://stackoverflow.com/a/62605993/230513 The output shows the code point, the expected binary representation of the UTF-8 encoding, the conversion to UTF-16, the incorrect UTF-8 conversion, and the correct UTF-8 conversion. $ gcc -v …gcc version 7.3.1 20180524 (for GNAT Community 2018 20180523) (GCC) $ gnatmake utftest.adb && ./utftest gcc -c utftest.adb gnatbind -x utftest.ali gnatlink utftest.ali Codepoint: 16#1D11E# UTF-8: 4: 2#11110000# 2#10011101# 2#10000100# 2#10011110# UTF-16: 2: 2#1101100000110100# 2#1101110100011110# UTF-8: 4: 2#11110000# 2#10011101# 2#10010000# 2#10011110# UTF-8: 4: 2#11110000# 2#10011101# 2#10000100# 2#10011110# OK