I am the maintainer of the MacPorts fossil package. We use the the source packages from your download page to assemble the MacPorts package. Starting with the version from 2011-05-23 15:11:12 the fossil build breaks for the i386 architecture on MAC OS X 10.6:

Undefined symbols for architecture i386:
"_fossil_fopen$UNIX2003", referenced from:
_do_meta_command in shell.o
_do_meta_command in shell.o
_do_meta_command in shell.o
_do_meta_command in shell.o
_sqlite3_shell in shell.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status
lipo: can't open input file: /var/tmp//ccijU7Dz.out (No such file or directory)
make: *** [fossil] Error 1


I was able to drill down the the offending change (compared to version 2011-05-12 14:56:52) to:

append opt " -Dfopen=fossil_fopen" in makemake.tcl

As a workaround you can change the MACOSX_DEPLOYMENT_TARGET to 10.5, which do not use the strange symbols with the $UNIX2003 suffix.

For more information about the symbols see http://developer.apple.com/library/mac/#releasenotes/Darwin/SymbolVariantsRelNotes/_index.html.

Also have look at the corresponding ticket in the MacPorts Bugtracker: see http://trac.macports.org/ticket/29591

drh added on 2011-05-28 17:53:50 UTC:
FWIW, I never had any problems building on MacOS 10.6.7. So I don't really understand this issue. But regardless, it is fixed now.