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.jrubyrc file not supporting `cext.enabled=true` #953

jwoertink opened this Issue Aug 13, 2013 · 4 comments


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jwoertink commented Aug 13, 2013

My default JRuby uses 1.9.3 mode. I added a .jrubyrc file to my project containing


Then I was able to do ruby -v and see it was in 2.0.0 mode. This verified that the .jrubyrc file was being read. I tried to install the ox gem, and got

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/jeremy/.rvm/rubies/jruby-1.7.4/bin/jruby extconf.rb 
NotImplementedError: C extension support is not enabled. Pass -Xcext.enabled=true to JRuby or set JRUBY_OPTS or modify .jrubyrc to enable.

I tried closing my terminal, and re-opening, but still got the error. After I did export JRUBY_OPTS=-Xcext.enabled=true I was able to bundle the gem. So it seems the .jrubyrc file just ignored that option.

My system:
jruby 1.7.4 (2.0.0) 2013-05-16 2390d3b on Java HotSpot(TM) 64-Bit Server VM 1.6.0_51-b11-457-11M4509 [darwin-x86_64]
OSX 10.8.4

@ghost ghost assigned BanzaiMan Aug 15, 2013

@BanzaiMan BanzaiMan closed this in f1a63bf Aug 15, 2013


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BanzaiMan commented Aug 15, 2013

The problem with the .jrubyrc approach is that, during gem installation, you would be in the fetched source's directory, not where you invoke jruby -S gem (or equivalent).

.jrubyrc does set the value correctly, but it just won't take effect when you want it.

$ cat > .jrubyrc                                
$ jruby -v -e 'puts ENV_JAVA["jruby.cext.enabled"]'
jruby (1.9.3p392) 2013-08-15 25edb17 on Java HotSpot(TM) 64-Bit Server VM 1.7.0_25-b15 [darwin-x86_64]

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jwoertink commented Aug 15, 2013

ah, ok. So really it only would work if that .jrubyrc was in my home directory, or something a bit more global as opposed to the project directory. Thanks!


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rbotafogo commented Mar 31, 2015

This is an old thread, but I´m having trouble with .jrubyrc. I´ve put it in my home directory and it doesn´t seem to change anything. I actually want to change the java heap size.



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headius commented Apr 6, 2015

@rbotafogo Please open a new issue if you're having problems with .jrubyrc on a current version of JRuby.

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