What's the best way to add a C include path when using `bundle install`?

user_107294 0
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As background, I have extensive knowledge of software build systems, Unix (I'm using Debian 11 in this instance) and Python environments, but almost no knowledge of modern Ruby environments.

I'm wanting to write a post in a friend's blog built with Jekyll and so am trying to get his blog building in development mode on my system. I'm wanting to minimise the amount of Ruby stuff I bring in using system packages, so I'm using bundle install --path vendor/bundle to set up the project dependencies, which include the rmagick gem.

I've installed the libmagickcore-6.q16-dev package, which gives me /usr/include/ImageMagick-6/wand/MagickWand.h. However, bundler is unable to install the RMagick 2.16.0 gem.

Looking in vendor/bundle/ruby/2.7.0/extensions/x86_64-linux/2.7.0/rmagick-2.16.0/mkmf.log, this seems to be the failure:

have_header: checking for wand/MagickWand.h... -------------------- no
                                                                                
"x86_64-linux-gnu-gcc -E -I/usr/include/x86_64-linux-gnu/ruby-2.7.0 -I/usr/include/ruby-2.7.0/ruby/backward -I/usr/include/ruby-2.7.0 -I.      conftest.c -o conftest.i"
conftest.c:3:10: fatal error: wand/MagickWand.h: No such file or directory      
    3 | #include <wand/MagickWand.h>                                            
      |          ^~~~~~~~~~~~~~~~~~~
compilation terminated.

Without doing extensive further investigation, I'm guessing that this is due to the include path being incorrect. This kind of hints at the RMagick gem being broken, since pkg-config does supply this:

$ pkg-config --cflags MagickCore
-fopenmp -DMAGICKCORE_HDRI_ENABLE=0 -DMAGICKCORE_QUANTUM_DEPTH=16 -I/usr/include/x86_64-linux-gnu//ImageMagick-6 -I/usr/include/ImageMagick-6

I'm not able to upgrade the Gems that he's using, nor even easily test that any changes I might make on my system work on the systems he's using. So to work around this I'd like to get bundle to add -I /usr/include/ImageMagick-6 (or do the moral equivalent).

What's the best way to make this happen? I don't see a bundle command line option for this. Perhaps there's an environment variable I can set?

rubygems ruby
1 Answers

It turns out that the RMagick was using the correct include paths, though these were not displayed in the mkmf.log file above. The issue was that I actually didn't have the include file itself, despite pkg-config --cflags MagickCore giving the path to the wand/ subdirectory.

I'd installed the Debian 11 package libmagickcore-6.q16-dev, which supplies MagickCore.pc, based on an earlier error indicating that pkg-config MagickCore was failing. However, the RMagic package actually requires a different library/set of headers, supplied by the libmagickwand-6.q16-dev package. After installing that, bundle appeared to build the RMagick gem without difficulty.

While debugging this I did come across a list of GCC environment variables, and it seems as if the C_INCLUDE_PATH one mentioned there might solve the original problem I'd posted above. However, I've no easy way of testing this right now.

user_1072940
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