Hi. Hopefully this is the right list for this question!
I am writing an extension for Ruby in C, and I need to determine
the endianness of the machine and set a flag when I compile. What is
the best way to go about this? I’ve seen examples of determining
endianness but I don’t know how to set the flag in extconf.rb
Any help would be greatly appreciated. Thank you!
–Aaron
Aaron P. wrote:
Modify $CFLAGS or $CPPFLAGS directly:
extconf.rb
if [1].pack(“I”) == [1].pack(“N”)
$CFLAGS += " -DBIG_ENDIAN" # note the leading space
end
/* In your C code somewhere /
#ifdef BIG_ENDIAN
/ Do something */
#endif
Regards,
Dan
On Tue, Dec 06, 2005 at 04:21:37AM +0900, Daniel B. wrote:
[snip]
#endif
Regards,
Dan
Thank you for the help!
–Aaron
Hi,
At Tue, 6 Dec 2005 04:21:37 +0900,
Daniel B. wrote in [ruby-talk:168948]:
extconf.rb
if [1].pack(“I”) == [1].pack(“N”)
$CFLAGS += " -DBIG_ENDIAN" # note the leading space
end
It tells the endian of the running platform, but not of the
target platform. They can differ when cross-compiling.
Since config.h defines WORDS_BIGENDIAN for big-endian
platforms, you don’t have to test it in extconf.rb.
On Tue, Dec 06, 2005 at 02:00:33PM +0900, nobuyoshi nakada wrote:
[snip]
Since config.h defines WORDS_BIGENDIAN for big-endian
platforms, you don’t have to test it in extconf.rb.
–
Nobu Nakada
I guess I don’t understand how I am supposed to set up my build
environment… As far as I can tell, config.h is generated while
building Ruby from source. The only config.h on my system is:
/usr/lib/ruby/1.8/i386-linux/config.h
Which does not have WORDS_BIGENDIAN listed in it. I did find
WORDS_BIGENDIAN in /usr/lib/ruby/1.8/i386-linux/defines.h but it just
says to look at BIG_ENDIAN.
Can you point me to a small project that I can model my build after, or
an example exconf.rb?
Thanks for the help!
–Aaron
On Wed, 2005-12-07 at 07:22 +0900, Aaron P. wrote:
environment… As far as I can tell, config.h is generated while
building Ruby from source. The only config.h on my system is:
/usr/lib/ruby/1.8/i386-linux/config.h
Which does not have WORDS_BIGENDIAN listed in it. I did find
WORDS_BIGENDIAN in /usr/lib/ruby/1.8/i386-linux/defines.h but it just
says to look at BIG_ENDIAN.
That’s because you are on Intel, which is little endian.
Can you point me to a small project that I can model my build after, or
an example exconf.rb?
What he is saying is that you should not modify your extconf.rb file. In
your C code, just do:
#ifdef WORDS_BIGENDIAN
// Big endian code
#else
// Little endian code
#endif
Guillaume.