[oneTBB backend] macOS < 10.13 with libc++ need `-fno-aligned-allocation`

[barracuda156]

@eddelbuettel Could we fix this? The issue arises only with OneTBB backend and Clang with libc++ on < 10.13 (that is why we did not face it earlier: legacy TBB was used until recently).

We could fix it for dependents of RcppParallel like this:
macports/macports-ports@627f0dd

But considering a number of affected ports, it is somewhat suboptimal solution.

(To be explicit, this should not be used with gcc and libstdc++ on any macOS versions, including < 10.13. Everything works fine there, and also the flag is Clang-specific.)

[barracuda156]

@kevinushey Maybe you could suggest something? We just need to ensure that the flag is passed to dependents as long as conditions are met (oneTBB, macOS < 10.13, Clang as the compiler).

@andrjohns Or maybe you could help?

[kevinushey]

In theory, we could add this check in the RcppParallel configure scripts here (perhaps via adding to PKG_CPPFLAGS or similar):

https://github.com/RcppCore/RcppParallel/blob/master/tools/config/configure.R

but macOS 10.13 itself is already EOL since January 2021. I'd welcome a PR but we won't have time to investigate ourselves.

[barracuda156]

Thanks, I will look into that. I need to fix it at least in MacPorts (alternative will be patching about a hundred ports, and then carry the patches, that will be bad). But if I come up with a neat fix, I submit the PR.

[barracuda156]

@kevinushey So not for submission here, but to fix it locally, I can just add this?

cxxflags <- "-fno-aligned-allocation"

We can patch this in conditionally on macOS version + clang being used (in MacPorts).

[kevinushey]

I think you might want to append it to the flags set by default from R; that is, in here:

RcppParallel/tools/config/configure.R

Lines 43 to 45 in 1e4fc54

	# work around issue with '-Werror=format-security' being specified without
	# a prior '-Wformat', which makes gcc angry
	cxxflags <- read_r_config(sprintf("%sFLAGS", cxx), envir = NULL)[[1]]

use something like cxxflags <- paste(cxxflags, "-fno-aligned-allocation")?