-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to Ralf Wildenhues on 11/22/2008 10:43 AM: >> -[m4_ifset([AS_MESSAGE_LOG_FD], >> +[m4_ifval(AS_MESSAGE_LOG_FD, > > If these kinds of changes are required in Autoconf code, it looks like > user code might be affected, too. Have you checked for third-party > instances of this? Also, is this an incompatibility to earlier > semantics?
The semantics should be identical for third-party use; this is merely an optimization change. m4_ifset([AS_MESSAGE_LOG_FD], [a], [b]) expands to: m4_ifdef([AS_MESSAGE_LOG_FD], [m4_if(m4_defn([AS_MESSAGE_LOG_FD]), [], [b], [a])], [b]) But since AS_MESSAGE_LOG_FD (if defined) must expand to either a number or the empty string, then it should generally be safe to expand AS_MESSAGE_LOG_FD rather than going through m4_defn (well, it is possible to have AS_MESSAGE_LOG_FD defined as [$[3]], as in my recent as_fn_error, but even that string is still safe for immediate expansion; and there were other places in m4sh that perform AS_MESSAGE_LOG_FD expansion). Also, by guaranteeing a definition from m4sh (rather than the previous semantics where it was undefined if the user didn't supply it), the m4_ifdef portion of m4_ifset is wasted effort. Which leaves us with the faster: m4_ifval(AS_MESSAGE_LOG_FD, [a], [b]) expanding to m4_if(AS_MESSAGE_LOG_FD, [], [b], [a]) - -- Don't work too hard, make some time for fun as well! Eric Blake [EMAIL PROTECTED] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Cygwin) Comment: Public key at home.comcast.net/~ericblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkkoYaMACgkQ84KuGfSFAYC0fACgn+HRGSOhTvjeQUf0v0RYlwB5 G60An2cMFcQ4p03fyhiWBsVZI4I6r5nv =Ekbo -----END PGP SIGNATURE-----
