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[R-pkg-devel] Compiler optimization flags with R package

4 messages · Guillaume Chapron, Dirk Eddelbuettel

Original
Guillaume Chapron
# 
Hello,

I am trying to debug some C code that is run only through a R package. I debug with lldb but I always get a message telling that the package "was compiled with optimization - stepping may behave oddly; variables may not be available.? And in fact, I cannot evaluate all variables and understand what is wrong. I have created a Makevars file in ~/.R/ that contains C=clang -O0 -g but it does not seem to change much. What should I do to make sure I can evaluate all variables in lldb? I am on a Mac and I wrote C=clang because I read that it produced much better error messages but I am happy to use gcc as well if this can be a solution.

Many thanks

Guillaume
Dirk Eddelbuettel
#
On 17 June 2017 at 21:32, Guillaume Chapron wrote:
| I am trying to debug some C code that is run only through a R package. I debug with lldb but I always get a message telling that the package "was compiled with optimization - stepping may behave oddly; variables may not be available.? And in fact, I cannot evaluate all variables and understand what is wrong. I have created a Makevars file in ~/.R/ that contains C=clang -O0 -g but it does not seem to change much. What should I do to make sure I can evaluate all variables in lldb? I am on a Mac and I wrote C=clang because I read that it produced much better error messages but I am happy to use gcc as well if this can be a solution.

Edit the file Makeconf in e.g.

     R> file.path(Sys.getenv("R_HOME"), "etc", "Makeconf")
     [1] "/usr/lib/R/etc/Makeconf"
     R> 

It has those settings hardwired from when R itself was compiled for you.  You
probably want to keep a copy of the original file to be able to revert.

Dirk
Guillaume Chapron
# 
Thanks!

In that file, I see:

CC = clang
CFLAGS = -Wall -mtune=core2 -g -O2 $(LTO)

will having -O0 instead give me all the variables or is there a flag for better debugging (I guess -g does it a little already)?

Thanks again
Dirk Eddelbuettel
#
On 18 June 2017 at 09:22, Guillaume Chapron wrote:
| Thanks!
| 
| In that file, I see:
| 
| CC = clang
| CFLAGS = -Wall -mtune=core2 -g -O2 $(LTO)
| 
| will having -O0 instead give me all the variables or is there a flag for better debugging (I guess -g does it a little already)?

Right, -g is what you need. I used to not alter -O flags for simplicity but
because code _could_ be reorganized for optimization it is not a bad idea to
use -O0 as well.

But the key is -g (just how there is -pg for profiling).

Dirk