Bug #17578
openmkmf experimental C++ Support
Description
I've been working on the Rice gem (https://github.com/jasonroelofs/rice) that wraps C++ code for use in Ruby.
I noticed that some c++ support was added to mkmf for Ruby 2.7. However, if I try to use it find a header it fails to work. For example:
find_header('rice.hpp')
The reason is the conftest uses gcc -E instead of g++ -E. To fix that requires overlading the cpp_command to support C++.
This the fix I have put in that works:
MakeMakefile['C++'].module_eval do
def cpp_command(outfile, opt="")
conf = cc_config(opt)
if $universal and (arch_flag = conf['ARCH_FLAG']) and !arch_flag.empty?
conf['ARCH_FLAG'] = arch_flag.gsub(/(?:\G|\s)-arch\s+\S+/, '')
end
RbConfig::expand("$(CXX) -E #$INCFLAGS #$CPPFLAGS #$CFLAGS #{opt} #{CONFTEST_CXX} #{outfile}",
conf)
end
end
The two changes over the default method are:
$(CC) -> $(CXX) -E
#{CONFTEST_c} -> #{CONFTEST_cxx}
Could this change be merged in? I can provide a patch file if you would like.
Last, it wasn't obvious to me how to activate the C++ support in mkfm. I ended up doing this:
include MakeMakefile['C++']
Is that correct?
Updated by shyouhei (Shyouhei Urabe) almost 4 years ago
- Description updated (diff)
- Status changed from Open to Assigned
- Assignee set to nobu (Nobuyoshi Nakada)
I guess recent 4b6fd8329b46701414aba2eeca10013cf66ec513 has something to do with it. @cfis (Charlie Savage) Can you try the current master? If that fixes your situation I guess we need to backport.
The canonical usage of MakeMakefile['C++']
is not clear to me either... We need @nobu's document.
Updated by cfis (Charlie Savage) almost 4 years ago
Thanks for the quick response.
I think that is different. try_cpp calls cpp_command:
def try_cpp(src, opt="", *opts, &b)
try_do(src, cpp_command(CPPOUTFILE, opt), *opts, &b)
...
end
And cpp_command is the function that needs to be overridden.
Updated by shyouhei (Shyouhei Urabe) almost 4 years ago
Yes try_cpp
is still a problem. I guess find_header
does not use try_cpp
though.
@nobu (Nobuyoshi Nakada) What do you think? It seems the problem exists and we need to take care.
Updated by cfis (Charlie Savage) almost 4 years ago
Just to be clear:
find_header calls try_header
try_header is an alias to try_cpp.
And try_cpp calls cpp_command.
Updated by shyouhei (Shyouhei Urabe) almost 4 years ago
cfis (Charlie Savage) wrote in #note-4:
Just to be clear:
find_header calls try_header
try_header is an alias to try_cpp.
And try_cpp calls cpp_command.
Yes, true for 2.7. The commit I mentioned before is basically changing try_header
's backend from try_cpp
to try_compile
.