Re: Bug in Regular Expressions when using colon as delimiter

Andreas Klussmann <andreas@infosys.heitec.net> wrote
> using
>    $x =~ m:(?:xx):;
> instead of
>    $x =~ m:(?\:xx):;
> terminates perl immediatly (not in the debuger) and gives
>    Sequence (?
> and nothing more as error message.

This illustrates at least three bugs:

i)   The message is truncated because of the "NUL in argument to die"
     problem which I reported some time ago (and provided a kludge for
     in Carp.pm).

ii)  In any case, it would have produced an incorrect error message.

iii) This error and many (most? all?) other parsing errors in regular
     expressions cause compilation to be terminated.

The attached patch fixes (i) and (ii) but not (iii).    It also extends
the regexp tests to test the error messages generated rather than just
note that an error has occurred.

Additional points which I'll leave to someone else:

a)  (iii) needs fixing.

b)  I note that many regexp error messages are incorrect, as they quote
    the regexp as /(?/ rather than as (e.g.) m:(?: or s:(?::.

c)  My understanding of Chip's rework of sprintf was that it now provided
    a mechanism for including strings with embedded NULs.   Could this
    be used to provide a complete fix for (i) rather than kludging each
    case as it turns up?

d)  I strongly suspect that the regexp tests   a\    and    'a\'i
    are not doing what the author intended.    I've left them so they
    say "ok" regardless.    (Hint:   \' is recognised in a '' string.)

p5p-msgid: E0wtbhv-0005Mm-00@ursa.cus.cam.ac.uk

1 files changed, 3 insertions, 0 deletions

diff --git a/regcomp.c b/regcomp.c
index 0e9846c2e6..3e302531e6 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -467,6 +467,9 @@ I32 *flagp;
 		nextchar();
 		*flagp = TRYAGAIN;
 		return NULL;
+            case 0:
+                croak("Sequence (? incomplete");
+                break;
 	    default:
 		--regparse;
 		while (*regparse && strchr("iogcmsx", *regparse))