bug#7574: [PATCH]: echo, printf, stat: Allow only up to 8 bit octal input for backslash-escaped chars

[Ondrej Vasik]

Hi,
as reported in RHBZ#660033
( https://bugzilla.redhat.com/show_bug.cgi?id=660033 ), echo, printf and
stat allows 3 octal digits without limitation to 8-bit.
Documentation(manpages, info) refers to "byte with octal value" or
"8-bit octal value". Therefore 9-bit octal values should not be allowed.
Especially in echo, only unsigned char is used for storing this octal
number, so 9-bit values overflow.
I see two ways of fixing : a) change documentation (informing only 1-3
octal digits input, no "8-bit" or "byte" words)
                           b) accept only up to 8-bit octals

Because of the unsigned char overflow, I prefer the 8-bit limit - and I
did so in attached patch. As I don't expect this will be noticed by
anyone (probably most of users already limit these octals to 8-bit
independently), I didn't added NEWS entry. Test testing printf '\0610'
output is added. Previously it was interpreted as 392 and this was
passed to putchar(), after the patch it is interpreted as '\061' + '0'
=> 10 .
I have also added missing \NNN GNU extension to --help output of echo.

Greetings,
          Ondrej Vasik

escaped-ninebit-octal-char.patch
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