13.14. Architectural Considerations

13.14. Architectural Considerations
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13.14.1. General Notes on Architectures

FreeBSD runs on many more processor architectures than just the well-known x86-based ones. Some ports have constraints which are particular to one or more of these architectures.

For the list of supported architectures, run:

cd ${SRCDIR}; make targets

The values are shown in the form TARGET/TARGET_ARCH. The ports read-only makevar ARCH is set based on the value of TARGET_ARCH. Port Makefiles should test the value of this Makevar.

13.14.2. Marking a Port as Architecture Neutral

Ports that do not have any architecture-dependent files or requirements are identified by setting NO_ARCH=yes.

Note:

NO_ARCH is meant to indicate that there is no need to build a package for each of the supported architectures. The goal is to reduce the amount of resources spent on building and distributing the packages such as network bandwidth and disk space on mirrors and on distribution media. Currently, however, our package infrastructure (e.g., package managers, mirrors, and package builders) is not set up to fully benefit from NO_ARCH.

13.14.3. Marking a Port as Ignored Only On Certain Architectures

To mark a port as IGNOREd only on certain architectures, there are two other convenience variables that will automatically set IGNORE: ONLY_FOR_ARCHS and NOT_FOR_ARCHS. Examples:
```
ONLY_FOR_ARCHS=	i386 amd64
```
```
NOT_FOR_ARCHS=	ia64 sparc64
```
A custom IGNORE message can be set using ONLY_FOR_ARCHS_REASON and NOT_FOR_ARCHS_REASON. Per architecture entries are possible with ONLY_FOR_ARCHS_REASON_ARCH and NOT_FOR_ARCHS_REASON_ARCH.

If a port fetches i386 binaries and installs them, set IA32_BINARY_PORT. If this variable is set, /usr/lib32 must be present for IA32 versions of libraries and the kernel must support IA32 compatibility. If one of these two dependencies is not satisfied, IGNORE will be set automatically.

13.14.5. Cluster-Specific Considerations

Some ports attempt to tune themselves to the exact machine they are being built on by specifying -march=native to the compiler. This should be avoided: either list it under an off-by-default option, or delete it entirely.
Otherwise, the default package produced by the build cluster might not run on every single machine of that ARCH.

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