[Bug-readline] Bug re: Unicode combining characters

[Keith Winstein]

Hello,

Readline 6.1 seems to have a problem when deleting a cell that consists of 
a Unicode base character followed by a combining character, if the next 
character in the line has the same base character.

It seems like it ignores the combining character (such as an accent), and 
takes a shortcut by deleting the cell *after* the one it's supposed to 
delete. This would be ok if the two cells really were identical, but it 
isn't if the first one has an accent attached to it and the second one 
doesn't.

How to reproduce:

(1) Run in a UTF-8 implementation-defined locale (like LANG=en_US.utf8) 
and a UTF-8 terminal emulator.

(2) Run readline-6.1/examples/rl

(3) Type "zyx̂xab".

(This string can be generated with perl -we '$|=1; binmode STDOUT, 
":utf8"; print "zyx"; print pack "U", 0x0302; print "xab\n"')

(4) Hit the left arrow three times.

(5) Hit the backspace key.

What you see: zyx̂ab

What you should see (and do see after Control-L): zyxab

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Please let me know if you need more information!

Best regards,
Keith