Description:
See https://bbs.archlinux.org/viewtopic.php?id=106469

rxvt-unicode-256color uses the '^?' key (ASCII DEL) as its default backspace key. See urxvt(1) (backspace key is '^?' if that resource is not set in ~/.Xdefaults) and also urxvt(7) (stating that urxvt follows the debian policy of using '^?' when unsure).

The terminfo entry for rxvt-unicode also reflects this:
"infocmp rxvt-unicode" gives kbs=\177 (ASCII DEL).

However, rxvt-unicode-256color uses the terminfo entry for rxvt-256color (it is compiled with the "--with-term=rxvt-256color" option), which uses '^H' as its backspace key.

The result is that ncurses programs that depend on a proper terminfo (and other programs that rely solely on the terminfo file) fail to detect the correct backspace key, unless the user changes the backspace key to '^H' by adding the entry "URxvt.backspacekey: ^H" in his ~/.Xdefaults.

I have created a simple patch "terminfo-256color.patch" that changes just 2 lines in the official urxvt terminfo file (idea from http://scie.nti.st/2008/10/13/get-rxvt-unicode-with-256-color-support-on-ubunut). I also just went ahead and created a new, working PKGBUILD to test it out. The tarball is attached.

By using the patched rxvt-unicode terminfo file, we not only solve the backspace key conflict problem, but also correctly tell all other ncurses/terminfo applications that we are using rxvt-unicode, and not rxvt. A simple visual check between "infocmp rxvt-256color" and "infocmp rxvt-unicode" reveals big featurewise differences that raise other conflict issues as well.

Additional info:
rxvt-unicode-256color 9.07-9

Steps to reproduce:
Do fresh install of rxvt-unicode-256color. Compile and run the following code with "gcc -o testkey -lncurses testkey.c":
#include <ncurses.h>
int main()
{
int ch;
initscr();
raw();
noecho();
clear();

printw("Press the backspace key now.");
ch = getch();
if (ch == KEY_BACKSPACE)
printw("You pressed the backspace key.");
else
printw("Unrecognized key.");

endwin();
return 0;
}

The if-statement will fail, because of aforementioned backspace key definition conflict from incorrect terminfo.