ruby/config.h file not found on macOS 15.7.1

[al3xandru]

Hi,

I was wondering if anyone has seen this issue before.
I am building Macvim from source using a script in which I have among other stuff CONFIGURE_OPTS += --enable-rubyinterp=dynamic.

On macOS 15.7.1, the build is failing with the following error:

In file included from if_ruby.c:119:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby.h:33:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby/ruby.h:24:10: fatal error: 'ruby/config.h' file not found
   24 | #include "ruby/config.h"
      |          ^~~~~~~~~~~~~~~

If I comment out the option, the build completes.

The final command looks like this:

cd macvim && ./configure --with-features=huge --enable-multibyte --enable-terminal --enable-cscope  --with-compiledby="5cb964beee@202510221124" --enable-pythoninterp=dynamic  --enable-python3interp=dynamic    --enable-perlinterp=dynamic --enable-rubyinterp=dynamic   --prefix=/opt/homebrew --enable-luainterp=dynamic --with-lua-prefix=/opt/homebrew --with-macarchs=arm64

Update: I'm seeing the following while configure runs:

checking --with-ruby-command argument... defaulting to ruby
checking for ruby... /usr/bin/ruby
checking Ruby version... OK
checking Ruby rbconfig... RbConfig
checking Ruby header files... /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0
checking libruby.dylib (arm64)... <none>

[ychin]

It seems to work for me. The key critical missing information here is what the actual compiler command is. For example when I configure mine similarly to yours, this is what shows up when I run make:

gcc -c -I. -DDYNAMIC_RUBY_DLL=\"libruby.dylib\"
-I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.5.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0
-I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.5.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/universal-darwin24
-DRUBY_VERSION=26 -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_MACVIM -Wall -Wno-unknown-pragmas -pipe  -DMACOS_X -DMACOS_X_DARWIN  -g -O2 -arch arm64 -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1
-o objects/if_ruby.o if_ruby.c

What do you see in your output?

[al3xandru]

It looks like the MacOSX sdks are different though. Yours is MacOSX15.5.sdk and mine is MacOSX26.0.sdk.
Might this mean different XCode versions? (I have no idea about such things)

[ychin]

Yes. We are using Xcode versions. If I have to guess maybe the version mismatch is an issue here. The configure script is using ruby (which in your case is /usr/bin/ruby) to determine its build info, but you are using a macOS 15 Ruby with Xcode 26 (with macOS 26 SDKs). I think if you use the same SDK as the OS itself it should work.

Is there a reason why you don't use Homebrew's ruby instead? That's usually easier IMO and you get more controls over what version to use (and much newer one as well).

[al3xandru]

This seems to be a fix:

cd /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.0.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/ruby/
sudo ln -s ../universal-darwin25/ruby/config.h