[R-SIG-Mac] openmp and xcode

[biii+rsigm@c m@iii@g oii 8p@wexpress@com]

If the CRAN R installation for macos includes |libomp.dylib|, is there a 
reason it does not include the paired |./include/omp*.h| files as well? 
It’s just three, they’re small, and it seems a reasonable step to making 
building packages that use OpenMP more direct.

Background: I’ve been having some difficulty compiling |data.table| 
(dev) on my MBP (M4, 15.4.1, R-4.4.3), due to an error (I do not assume 
it’s this package, I’ve had trouble with other packages too).

|symbol not found in flat namespace '___kmpc_dispatch_deinit' |

When troubleshooting this, I’ve verified that I have Xcode, but it is 
version 16.3, well past the 14.3 used for R-4.4.3. Sleuthing some more, 
I realized that it’s an easy mistake to update the 
|/usr/local/lib/libomp.dylib| file to be a different version than what 
is distributed in CRAN’s R. I don’t see an easy way to change version 
within XCode, and when I tried installing XCode-14.3 it says my OS does 
not support that (old) version. (Even with gfortran 12.2, I can’t fix 
that error, but that’s a different subject.)

I recognize the challenge in distributing binaries for multiple versions 
of macos and xcode. I believe R-4.5 is still being built on XCode-14.3, 
which begs another question of if/when XCode updates are planned for R 
binaries and CRAN. (Big topic, I understand, I did not find a recent 
discussion. My apologies if I missed something.)

Thanks,
Bill

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