parrot smoke-me/illegal-escape-gh1103

[Reini Urban]

parrot wants to change its behavior with illegal escape sequences with 6.9.0
See https://github.com/parrot/parrot/issues/1103

parrot and rakudo smoked fine with this branch,
and it helps finding imcc parser bugs, esp. .lex quoting issues.,
tracked in GH #1095, which was found by this perl6
https://rt.perl.org/Public/Bug/Display.html?id=116643

Previously:
Silently ignore illegal escapes for a-zA-Z
and change the string from "foo\o" to "fooo"

Now:
Throw "Illegal escape sequence \o in foo\o"

The C standard requires such "invalid" escape sequences to be diagnosed
(i.e., the compiler must print an error message). Parrot behaved strange,
and hence imcc parser quoting bugs were never fixed.

Parrot_str_unescape()
Unescapes the specified C string. These sequences are covered:

  \xhh        1..2 hex digits
  \ooo        1..3 oct digits
  \cX         control char X
  \x{h..h}    1..8 hex digits
  \uhhhh      4 hex digits
  \Uhhhhhhhh  8 hex digits
  \a, \b, \t, \n, \v, \f, \r, \e

These sequences are not escaped: C<\\ \" \' \?>

All other escape sequences within C<[a-zA-Z]> are illegal.

This printed ok 4 instead of ok 3:

.sub 'main' :main
    $S0 = 'bar\o'
    $P1 = box 'ok 1'
    set_global $S0, $P1
    $P2 = get_global 'bar\o'
    say $P2

    $S1 = "foo\\o"
    $P1 = box 'ok 2'
    set_global "foo\\o", $P1   # ok, parsed as "foo\\o"
    $P2 = get_global "foo\\o"
    say $P2

    $S2 = "foo\o"
    $P1 = box 'ok 3'
    $S3 = "fooo"
    $P2 = box 'ok 4'
    set_global "foo\o", $P1    # wrong, parsed as "fooo"
    set_global "fooo",  $P2
    $P3 = get_global "foo\o"
    say $P3

    $P3 = get_global "fooo"
    say $P3
.end

but the real problem is with double-quoted .lex names.

What do you think? Should I allow illegal escape chars for one
deprecation cycle, just warn once?
Or change it right away? I'd go for right away.

-- 
Reini Urban
http://cpanel.net/   http://www.perl-compiler.org/