[Rd] suppressing "global" cppflags in an individual package

Kasper Daniel Hansen khansen at stat.Berkeley.EDU
Thu May 11 06:37:01 CEST 2006

Thank you Simon, a little comment below

On May 9, 2006, at 2:49 PM, Simon Urbanek wrote:

> On May 9, 2006, at 1:11 PM, Kasper Daniel Hansen wrote:
>> It is indeed the case that after updating to GCC 4 the package  
>> gets  broken using -O2. I agree this needs to be fixed, but the error
>> [...]
>> unfortunately), but reading your comment about CPPFLAGS and  
>> CXXFLAGS makes me think I can indeed override it using the package  
>> Makevars file. The flags I was passing to the compiler were  
>> library locations anyway which was for the preprocessor.
> AFAIR you cannot override CPPFLAGS/CXXFLAGS in Makevars, because it  
> gets included first. You can, however, use something like this:
> all: $(SHLIB)
> %.o: %.c
>         $(CC) $(ALL_CPPFLAGS) $(ALL_CFLAGS) $(MYCFLAGS) -c $< -o $@
> for C, or for C++ accordingly:
> %.o: %.cc
>         $(CXX) $(ALL_CPPFLAGS) $(ALL_CXXFLAGS) $(MYCXXFLAGS) -c $< - 
> o $@

Actually you do not need the all: line, and since I use .cpp as C++  
extension, all I needed was

%.o: %.cpp
<TAB>$(CXX) $(ALL_CPPFLAGS) -O0 -c $< -o $@

Note that I needed to delete the $(ALL_CXXFLAGS) which basically  
reads R's flags.

Now, is there any way to (in the Makevars file) operate on $ 
(ALL_CXXFLAGS), since all I want is to delete any -O* flag? Or is  
defining rules and variables all I can do?

Actually, where do I read about the Makevars syntax. Is it from  
autoconf (of which I only now the name). The section on it in R-exts  
is useful (hey, I managed to make one in the first place), but not  


> However, don't ask me how portable this is ;). It exploits the fact  
> that old-style rules .c.o used by Makeconf are overridden by the  
> new-style rules regardless of their position. Nevertheless, you  
> could still use specific rules if desired without a full-blown  
> Makefile. (I always recommend the use of Makevars as far as  
> possible, because most writers of Makefiles get the shlib  
> compilation wrong).
> Cheers,
> Simon

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