[R-sig-Debian] LTO flags in 4.1.0 Ubuntu 21.04 Makeconf

[Karl Dunkle Werner]

Hello,

I noticed the Makeconf file that comes with the Ubuntu version of R 4.1.0
has link-time optimization (LTO) flags enabled. For instance:
CXX11FLAGS = -g -O2 -ffile-prefix-map=/build/r-base-aXXzqd/r-base-4.1.0=.
-flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat
-Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)

If I understand things correctly, these flags cause a bit of a problem
trying to install the arrow package, since that package does not want to
override the CXX11FLAGS, but also does not work with LTO. Setting "UseLTO:
false" in the package description doesn't seem to work.
Would it be possible to remove the flags -flto=auto and -ffat-lto-objects?

See https://issues.apache.org/jira/browse/ARROW-12853 for a discussion of
installation with these flags and
https://issues.apache.org/jira/browse/ARROW-9616 for a broader discussion
of LTO in Arrow.

My apologies if this is the wrong place to report this kind of issue.

The entire Makeconf file is attached to the first of those Arrow issues:
https://issues.apache.org/jira/secure/attachment/13025950/Makeconf_local
The file appears in the package
https://cloud.r-project.org/bin/linux/ubuntu/hirsute-cran40/r-base-core_4.1.0-1.2104.0_amd64.deb.
These flags are not set in the Debian Bullseye version (
https://cloud.r-project.org/bin/linux/debian/bullseye-cran40/r-base-core_4.1.0-1~bullseyecran.0_amd64.deb)
or the Ubuntu 20.10 version (
https://cloud.r-project.org/bin/linux/ubuntu/groovy-cran40/r-base-core_4.1.0-1.2010.0_amd64.deb
).
(For anyone who is unfamiliar, as I was, the Makeconf file is in
data/etc/R/, after extracting both the deb package and the data.tar.xz
directory.)


Thank you,
Karl

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