-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 According to Paolo Bonzini on 10/17/2008 6:41 AM: > I still cannot understand why the diversion ends up like this though. > > Here is an even smaller testcase: > > AS_INIT > m4_defun([AS_FROBIT_PREPARE], [frob=1]) > m4_defun([AS_FROBIT], [AS_REQUIRE([AS_FROBIT_PREPARE])$1]) > m4_defun([AS_DOIT], [: $1]) > m4_define([XXFOO], [AS_FROBIT(exit 1)]) > AS_DOIT(XXFOO) > > which gives > > : frob=1 > exit 1 > > as is, and > > frob=1 > : exit 1 > > when XXFOO is quoted. > > So, if this is a bug (and it looks like one, though very minor because > proper quoting works around it) we also have a testcase. :-)
This is a limitation of m4 diversions. Something even simpler: $ echo 'm4_define([foo],[m4_divert(1)hi m4_divert(0)])m4_divert[]foo:' | m4 -Ilib m4sugar/m4sugar.m4 - : hi $ echo 'm4_define([foo],[m4_divert(1)hi m4_divert(0)])m4_divert[]m4_echo(foo):' | m4 -Ilib m4sugar/m4sugar.m4 - hi : The point is that text goes into a diversion only when _you are not doing argument collection_ - in other words, the macro call must be expanded at the outermost level. Any macro that potentially changes the current diversion must be quoted, rather than expanded in advance, when handed as an argument to another macro; otherwise, the text output while the diversion change is in effect doesn't go to the changed diversion, but to the argument collection. M4 1.6 will add an optional argument to the divert builtin, such that divert(1,text) places text in diversion 1, regardless of whether it is being expanded during argument collection. But unfortunately, we cannot rely on that. Alas, m4 lacks the ability to inform you when a macro is being expanded during argument collection, so we can't even protect against these sorts of subtle diversion bugs (maybe I should add a macro that expands to the current nesting depth?). - -- 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 iEYEARECAAYFAkj4jB8ACgkQ84KuGfSFAYCjMwCgnBIjug/gOs5Dczqp7Mk8Dm2L 0qYAnixI6hsUVLiwDDkbLtqNKD2to7d3 =aaR6 -----END PGP SIGNATURE----- _______________________________________________ m4-discuss mailing list m4-discuss@gnu.org http://lists.gnu.org/mailman/listinfo/m4-discuss
