On Aug 23, 2019, at 11:58, Bill Cole wrote:
> I'm having apparently initial success from doing a 'port -n upgrade outdated'
> but that makes me a bit nervous...
It should make you nervous. You probably shouldn't run that unless you know
exactly why each port is outdated and what rebuilding it will do.
"-n" tells MacPorts not to upgrade dependencies first. But the whole reason why
a port was updated may be because of changes in one of its dependencies.
Consider: perhaps ImageMagick is updated to a new version. That new version has
new library versions, which means everything using ImageMagick libraries needs
to be rebuilt, so their revisions are increased [1], so they show up as
outdated. If you upgrade one of those ports that depends on ImageMagick (let's
call it "X") normally using "sudo port upgrade X", MacPorts upgrades
ImageMagick first, then upgrades port X so that it now links with the new
library. All is well. But if you instead run "sudo port -n upgrade X", without
having first upgraded ImageMagick, then port X would rebuild against the old
libraries, defeating the purpose of the upgrade. Or you might have received a
binary of the new X from our server, where ImageMagick was upgraded first. Now
you have a version of X installed that links with versions of the ImageMagick
libraries newer than the ones you have, which means the program will not work.
If you have rev-upgrade turned on, MacPorts will detect X as broken and will
rebuild X, and I forget what happens here: either MacPorts will do a
from-source build and you'll be left back in the first situation of having
defeated the purpose of the upgrade, or it will repeatedly download the binary
from our server, until after a number of attempts it gives up. When you finally
do upgrade ImageMagick to the new version later, now X and everything else you
upgraded before while ignoring dependencies will be broken, leading to another
rev-upgrade cycle.
Not all situations are like that. You mentioned cmake, which is a configuration
tool. If a program requires cmake to configure, and you have cmake installed,
even if it's a slightly older version, it's probably alright if you don't
upgrade it first. cmake is just a program; it doesn't have any libraries that
other programs use, so library version mismatches aren't a possibility.
MacPorts doesn't know the specifics of any port, so it assumes that it should
upgrade all of a port's dependencies first.
So using the "-n" flag when upgrading can be safe in some circumstances, but
since it can be difficult to figure out whether a particular upgrade matches
those circumstances, especially since it depends on what other ports are
outdated on your system which depends on how recently you last upgraded your
ports, the safest advice is not to use the "-n" flag when upgrading.
[1] Here is an example of that situation:
https://github.com/macports/macports-ports/pull/5016
