What is the FreeBSD situation?

[Jacob Carlborg]

On 2017-11-03 03:43, Jonathan M Davis wrote:

> So, I fully expect that there are times when being able to version the
> source code based on the OS version (or the libc version if you're talking
> about Linux) would be needed. However, I don't know if it's needed often
> enough for the compiler to directly support it rather than using custom
> version specifiers for those code bases that do. Technically, I think that
> the versioning that they do in C/C++ for this sort of thing with #includes
> is more or less equivalent to using custom version specifiers rather than
> actually doing anything special with the compiler.
> 
> Regardless, it would be nice if we could avoid the need to statically
> version any code in dmd, druntime, or Phobos based on OS version.

I don't know all the details, just throwing some ideas out there:

* macOS went through a similar transition, perhaps have a look at how 
Apple did that. There some information here [1], scroll down to the 
documentation for the _DARWIN_FEATURE_64_BIT_INODE macro

* Fully statically link the binaries, including the C standard library. 
Might work assuming the kernel did not change

* Do something similar to what AppImage [2] is doing on Linux. AppImage 
works by creating a binary with an executable header and a disk image 
that holds the payload. In the case of AppImage the payload would be the 
application including all the files necessary to run it. Perhaps we 
could instead build something like universal binaries on macOS. Embed 
two separate executables and run one of the depending on the current system

[1] 
https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man2/stat.2.html

[2] https://appimage.org

-- 
/Jacob Carlborg