I have a nightly cron set up to run this command:
/usr/local/bin/sa-update && /usr/local/bin/sa-compile

When sa-compile is run this way via cron, the sa-compile portion of this fails 
with the following error:

re2c -i -b -o scanner1.c scanner1.re
Can't exec "re2c": No such file or directory at /usr/local/bin/sa-compile line 
281, <$fh> line 2622.
command failed! at /usr/local/bin/sa-compile line 282, <$fh> line 2622.

This appears to be caused by the following line in the sa-compile code: 'my 
$cmd = "re2c -i -b -o scanner$_.c scanner$_.re";'.  When jobs are run from 
cron under our FreeBSD setup (and I suspect on most others), they require the 
full path to commands to be specified - ex. /usr/local/bin/re2c rather than 
just re2c.  

I've resolved this issue locally by updating that line in sa-compile to 
read "my $cmd = "/usr/local/bin/re2c -i -b -o scanner$_.c scanner$_.re";

Please change future release of Spamassassin to include the full path to re2c 
in the code for sa-compile.

Thanks!