re_compile_pattern change

[jeff]

In gettext-0.16.1 and findutils-4.2.29, the version of autoconf used was
2.61 and 2.60a respectively. gettext-0.14.5, findutils-4.2.27, tar-1.16.1,
coreutils-5.96, diffutils-2.8.1, grep-2.5.1a, and inetutils-1.5 all used
2.60 or older. The reason I bring this up is that the outcome of
re_compile_pattern has changed somewhere between 2.60 and 2.60a and I
don't know if it is a bug in the newer autoconf (>2.60), or a
long-standing bug in the older versions of autoconf (<=2.60).

One difference I noted in the test code used between tar-1.16.1 and
findutils-4.2.29 (2.60 vs 2.60a) was:

tar:       s = re_compile_pattern ("a[[:]:]]b\n", 11, &regex);
findutils: s = re_compile_pattern ("a[:]:]b\n", 9, &regex);

A printf in both shows that tar says "Invalid character class name" as the
comment in the code says it should. findutils says null causing an exit
code of 1 and the test to fail.

I do not know which behavior is correct. Can someone shed some light on
this, please? I'm not subscribed, so please CC.

Thanks!