Regex parenthesis handling bug

[Neil Jerram]

According to the libc manual, all libc regex settings default to the
Emacs behaviour, so unquoted parens should match literal parens in the
match string, while quoted parens indicate grouping.

In Guile, it doesn't work like this...

guile> (string-match "\\(x\\)" "x")
$3 = #f
guile> (string-match "x" "x")
$4 = #("x" (0 . 1))
guile> (string-match "(x)" "x")
$5 = #("x" (0 . 1) (0 . 1))
guile> (string-match "(x)" "(x)")
$7 = #("(x)" (1 . 2) (1 . 2))
guile> (string-match "\\(x\\)" "(x)")
$8 = #("(x)" (0 . 3))
guile>

I don't think this is a Guile bug, because Guile's regex functions
fall straight through to libc.  Does anyone know if this is a known
libc bug, and whether there is a nice workaround?

Thanks,
        Neil