Release build for Rcpp package

Question

I want to make a release build for an R package that uses Rcpp, but when I look at the arguments to g++, I see that even though I have a -O3 flag in my Makevars file, Rcpp is overriding this with a -O0 flag at the end, for example I'm seeing this as output

g++ -std=gnu++11 -I"/usr/share/R/include" -DNDEBUG -I"/home/dz5937/R/x86_64-pc-linux-gnu-library/3.6/Rcpp/include" -I"/home/dz5937/R/x86_64-pc-linux-gnu-library/3.6/RcppEigen/include" -O3 -std=c++14 -fpic -g -O2 -fdebug-prefix-map=/build/r-base-jbaK_j/r-base-3.6.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g -UNDEBUG -Wall -pedantic -g -O0 -c btsatr.cpp -o btsatr.o

How can I make Rcpp do a release build, i.e. higher optimization level than -O0?

This is what I have in my Makevars file

PKG_CXXFLAGS = -O3 -std=c++14

Dirk Eddelbuettel Dirk Eddelbuettel · Accepted Answer · 2020-10-23T21:43:05

That to has come up before but you "can't" short of locally and one-off editing your Makevars for R.

So the short answer (and here I am going to use the path on my Debian / Ubuntu system which has a handy shortcut of /etc/R as a softlink into R's own etc/ directory):

edd@rob:~$ grep -- '-g' /etc/R/Makeconf | grep -v "^#"
CFLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
CXXFLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
CXX11FLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
CXX14FLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
CXX17FLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
CXX20FLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g $(LTO)
FCFLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong $(LTO_FC)
FFLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong $(LTO_FC)
SAFE_FFLAGS = -g -O2 -fdebug-prefix-map=/build/r-base-8T8CYO/r-base-4.0.3=. -fstack-protector-strong -msse2 -mfpmath=sse
TCLTK_LIBS = -L/usr/lib/x86_64-linux-gnu -ltcl8.6 -L/usr/lib/x86_64-linux-gnu -ltk8.6 -lX11 -lXss -lXext
edd@rob:~$

This is (in essence) a combination of three sources:

things that R itself hardwires
things that the distribution hardwires for gcc and friends
things that package maintainer (me, actually) specifies for the distro

All this sets your CXXFLAGS (and same for CXX11... CXX14... ...). You can then set

your user-local values via ~/.R/Makevars
your package-local values via src/Makevars

The really weird thing is that even after the almost 25 years that we have no mechanism to edit and override this and selectively undo. I think I recall that for gcc et al the rightmost value wins...

So to sum up, to be "sure" you'd have to edit out the -O0 value in your machine-local config file.

Release build for Rcpp package

1 Answers