-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to Mike Frysinger on 4/5/2009 7:19 PM: >> i'm not an expert by any means with internal autoconf/m4. if there's a m4 >> helper function to test whether an argument contains something other than >> whitespace, then the change to m4sh.m4:_AS_IF is trivial ... use that >> rather than m4_ifvaln([$1],.... > > to answer my own question and to post a patch, m4_normalize can be used: Indeed. However, m4_normalize is an expensive choice for doing this check (it involves regular expressions). I'm thinking of introducing a new m4sugar macro (untested in this email) that can be used for this purpose with less overhead - any suggestions for a better name? # m4_ifblank(COND, [IF-BLANK], [IF-TEXT]) # --------------------------------------- # If COND is empty, or consists only of blanks (space, tab, newline), # expand IF-BLANK, else expand IF-TEXT. m4_define([m4_ifblank], [m4_if(m4_translit([[$1]], [ ][ ][ ]), [], [$2], [$3])]) Hmm, this means that in addition to differing on a COND consisting of just whitespace, m4_ifval and m4_ifblank have opposite if-then sense: m4_ifval([$1], [$1], []) m4_ifblank([$1], [], [$1]) Is it worth trying to think of a better macro name so that both macros will favor the second (rather than the third) argument when the first argument is not empty? > > this should "fix" every macro that uses AS_IF with an "else" argument. it > certainly fixes my test case. I think you are right that fixing AS_IF to detect blank instead of empty arguments when performing optimizations will probably help a number of poorly-written configure.ac, so I will probably be checking in a patch along these lines soon. Note, however, that this still doesn't help situations like: AS_IF([foo], [AC_REQUIRE([bar])]) since the presence of AC_REQUIRE will trigger the IF-TEXT expansion, although the subsequent expansion pass will result in a blank body. - -- Don't work too hard, make some time for fun as well! Eric Blake ebb9@xxxxxxx -----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 iEYEARECAAYFAknZ/LMACgkQ84KuGfSFAYC1EACfY4IEyfl+qWBBnwRAQdrTiTxQ 11YAoMrXfwB7HZVbYFoz/CypJ1xar6Y6 =QqeD -----END PGP SIGNATURE----- _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
