How can I install a MacPorts port that is linked with an earlier MacOS release?

[Ryan Schmidt]

On Mar 13, 2019, at 16:12, Mojca Miklavec wrote:

> Dear Michael,
> 
> On Wed, 13 Mar 2019 at 16:03, Michael A. Leonetti wrote:
>> 
>> How an I install the port packages that support El Capitan (or any specific
>> MacOS version) and above to link against?
> 
> By far the least painful way would be to install El Capitan inside a
> VM and build there.

I'll second that. If you want to install ports that will run on El Capitan or later, the most straightforward way to accomplish that is to do it on a machine running El Capitan.


> The other option would be to contribute patches to provide better
> support for doing these kind of builds (which would in fact be
> useful). You can ask MacPorts to do universal builds, you can ask it
> to link against a different SDK etc., but it mostly lacks better
> support for building for an older OS. When I tried to do some
> bootstrapping for 10.5 on 10.6 one of the biggest issue was that the
> ports sometimes use code that is only executed on a particular OS
> version. Even if you set the environmental variables to link against
> an older SDK, define the variable for the target OS etc. ... you might
> still be bitten by those if-else parts of the code that check what
> your current OS is, not the OS you want to target.
> 
> Personally I would welcome patches to fix that, but that would
> probably take quite some effort.

MacPorts has support for building for older systems, but individual ports may not support it. If you find any ports that don't support it, it is a bug that should be fixed.

You will want to begin by uninstalling any ports you had already installed, and set "buildfromsource always" in macports.conf so that you don't get pre-compiled binaries from our server which were not built for the OS version you requested. Or you may want to use a separate MacPorts installation for this project, configured to use a nonstandard prefix; in that case, "buildfromsource always" is the default; binaries are not available for nonstandard prefixes.

You can set e.g. "macosx_deployment_target 10.11" in macports.conf. MacPorts passes this value to every phase of every port's build as an environment variable, so it's difficult for a port to ignore it. The only ports that would not handle this correctly are those whose portfile or build systems override this. We have often found build systems with hardcoded deployment targets. We should clear those when we find them to allow the MacPorts setting to be used.

You can also set macosx_sdk_version in macports.conf, but Apple recommends that you always build with the latest SDK regardless what OS you're targeting, so ideally it should not be necessary to change the SDK version. If it is necessary to change it, you will probably find many more ports that do not honor this setting, since each port must individually support it by passing the required values on to the build system via variables like CFLAGS, CXXFLAGS, LDFLAGS. MacPorts handles this correctly for autotools ports, and the cmake portgroup handles it for ports using cmake, but there are many nonstandard build systems out there that handle it in their own way, which it is up to the portfile author to correctly determine and account for.

And Mojca correctly mentioned that many ports that vary their behavior based on OS version do so based on the build OS version, rather than the deployment OS version, which in some cases is probably not the correct thing to do. Each instance of an OS version comparison in each Portfile would have to be examined to see if it is correct or needs to be changed.


P.S: Michael, if you have further questions, please write to the mailing list addresses at lists.macports.org, rather than the older domain name you used which was retired in 2016. The older domain still forwards to the new one, but some users cannot read those forwards due to restrictions imposed by their email service providers.