[bug-gnulib] Re: bugs in regexp.c

[Paul Eggert]

Sam Steingold <address@hidden> writes:

> I think it is a good practice to treat undefined behavior as an
> error.

That may be, but in that case the test cases assuming a particular
extension tof POSIX, and the test cases therefore will not be portable
to all POSIX implementations.  I suspect that in some cases the
regexp.c behavior is compatible with traditional UNIX, which did not
always treat undefined behavior as an error; changing it might break
applications assuming the traditional UNIX behavior.

>        (regcomp (&r, "$*", REG_EXTENDED) != 0)

Ah, OK, I see now.  That has undefined behavior.  "$*" is a valid BRE,
but it is not a valid ERE.

<http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04_06>
defines the behavior of "*" only if it is preceded by "an ERE matching
a single character or an ERE enclosed in parentheses".  But "$" is not
such an ERE.