Success!

Forcing the linking of the shared library in Sketchup.app was the trick (can't just add it to the library search path).

For other cmake users, here's the CMakeLists.txt fragment that did the trick:

CMakeLists.txt

...
find_package(Ruby REQUIRED)
if(HAVE_SKETCHUP)
    set(SKETCHUP "/Applications/Google\ SketchUp\ 7/SketchUp.app")
    set(SKETCHUP_RUBY "${SKETCHUP}/Contents/Frameworks/Ruby.framework")
    set(SWIG_RUBY_LIB "${SKETCHUP_RUBY}/Ruby")
else()    
    set(SWIG_RUBY_LIB "${RUBY_LIBRARY}")
endif()    

swig_add_module(${RUBY_MODULE_NAME} ruby "${INTERFACE_FILES}")
include_directories(${RUBY_INCLUDE_PATH})
swig_link_libraries(${RUBY_MODULE_NAME} "${MYEXTENSION_LIB}" "${SWIG_RUBY_LIB}") 
...

Interestingly, when linking against this, MacOS is smart enough to encode the path to the Ruby library relative to the executable, so that if Sketchup.app is installed in a different location, it still works fine:

otool -L MyExtension.bundle

	@executable_path/../Frameworks/Ruby.framework/Versions/A/Ruby (compatibility version 1.8.0, current version 1.8.5)
	/usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current version 7.4.0)
	/usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 111.0.0)

I hope someone else finds this useful. I'm glad I don't have to resort to a client/server type implementation and associated headaches.

Thanks for all your help!

Simeon

@jim said:

I thought SketchUp used the already installed Ruby on Macs, and ships with a .dll on Windows?
...

While Ruby is included in modern MacOS versions, applications can have their own versions (of most any library) in their application bundle. In this case it's "SketchUp.app/Contents/Frameworks/Ruby.framework". Compared to the system Ruby Framework, it's very sparse:

Sketchup.app/Contents/Frameworks

Ruby.framework
Ruby.framework/Resources
Ruby.framework/Ruby
Ruby.framework/Versions
Ruby.framework/Versions/A
Ruby.framework/Versions/A/Resources
Ruby.framework/Versions/A/Resources/English.lproj
Ruby.framework/Versions/A/Resources/English.lproj/InfoPlist.strings
Ruby.framework/Versions/A/Resources/Info.plist
Ruby.framework/Versions/A/Ruby
Ruby.framework/Versions/Current

/System/Library/Frameworks

Ruby.framework
Ruby.framework/Headers
Ruby.framework/Resources
Ruby.framework/Ruby
Ruby.framework/Versions
Ruby.framework/Versions/1.8
Ruby.framework/Versions/1.8/Headers
Ruby.framework/Versions/1.8/Headers/config.h
Ruby.framework/Versions/1.8/Headers/defines.h
Ruby.framework/Versions/1.8/Headers/digest.h
Ruby.framework/Versions/1.8/Headers/dl.h
Ruby.framework/Versions/1.8/Headers/dlconfig.h
Ruby.framework/Versions/1.8/Headers/dln.h
Ruby.framework/Versions/1.8/Headers/dtrace.h
Ruby.framework/Versions/1.8/Headers/env.h
Ruby.framework/Versions/1.8/Headers/intern.h
Ruby.framework/Versions/1.8/Headers/missing.h
Ruby.framework/Versions/1.8/Headers/node.h
Ruby.framework/Versions/1.8/Headers/re.h
Ruby.framework/Versions/1.8/Headers/regex.h
Ruby.framework/Versions/1.8/Headers/ruby.h
Ruby.framework/Versions/1.8/Headers/rubyio.h
Ruby.framework/Versions/1.8/Headers/rubysig.h
Ruby.framework/Versions/1.8/Headers/st.h
Ruby.framework/Versions/1.8/Headers/util.h
Ruby.framework/Versions/1.8/Headers/version.h
Ruby.framework/Versions/1.8/Resources
Ruby.framework/Versions/1.8/Resources/English.lproj
Ruby.framework/Versions/1.8/Resources/English.lproj/InfoPlist.strings
Ruby.framework/Versions/1.8/Resources/Info.plist
Ruby.framework/Versions/1.8/Resources/version.plist
Ruby.framework/Versions/1.8/Ruby
Ruby.framework/Versions/1.8/usr
Ruby.framework/Versions/1.8/usr/bin
Ruby.framework/Versions/1.8/usr/bin/erb
Ruby.framework/Versions/1.8/usr/bin/gem
Ruby.framework/Versions/1.8/usr/bin/gem_mirror
Ruby.framework/Versions/1.8/usr/bin/gemlock
Ruby.framework/Versions/1.8/usr/bin/gemri
Ruby.framework/Versions/1.8/usr/bin/gemwhich
Ruby.framework/Versions/1.8/usr/bin/irb
Ruby.framework/Versions/1.8/usr/bin/rdoc
Ruby.framework/Versions/1.8/usr/bin/ri
Ruby.framework/Versions/1.8/usr/bin/ruby
Ruby.framework/Versions/1.8/usr/bin/testrb
Ruby.framework/Versions/1.8/usr/bin/update_rubygems
Ruby.framework/Versions/1.8/usr/lib
Ruby.framework/Versions/1.8/usr/lib/libruby.1.dylib
Ruby.framework/Versions/1.8/usr/lib/libruby.dylib
Ruby.framework/Versions/1.8/usr/lib/ruby
Ruby.framework/Versions/1.8/usr/share
Ruby.framework/Versions/1.8/usr/share/ri
Ruby.framework/Versions/Current
...
(continues for ~37,000 more lines)

The fact that Google doesn't include the header files that it used in its version of the ruby runtime makes it a little bit tricky to compile with Swig (and cmake, in my case); you kinda have to mix and match Framework components.

Simeon

@runnerpack said:

...
Ideally, you would link to the actual library included in the SU installation. I think on OSX it would be called "libruby-1.8.dylib" (or something like that).
...
A bit long-winded, but I hope it helps

Actually it helps quite a bit. Pointing out that the ruby runtime was "minimalist" is a good hint. On MacOS the libraries, resources, etc. are provided as "Framework" bundles. Normally a Framework bundle contains the header files and libraries, and older versions of Sketchup had the "minimalist" header files. Now even those are missing, leaving the Framework bundle as mostly empty directories with the exception of a single file called "Ruby", which is (confusingly) the shared library and not the interpreter (no idea why they leave the extension off in Frameworks).

So that's my long-winded way of saying that your arm-chair analysis gives me a coule things to try out Thanks!

Simeon

@thomthom said:

Checked in SU7.1 just to be sure they haven't updated it:

` Object::RUBY_VERSION

1.8.0`

I should have been clear about versions:

I'm running Sketchup 7.1 (7.1.4870) on MacOS 10.5.8. This is what I get from the ruby console:
> Object::RUBY_VERSION 1.8.5

I'm hoping for someone to share some tips on how to efficiently link C++ code into Sketchup via the Ruby scripting engine. We are currently using Swig, which works fine in a stand-alone Ruby interpreter, but crashes Sketchup when loaded via the Sketchup console or as an extension.

Our C++ library that has been successfully used via Ruby (and Python) via Swig generated bindings. The code has been tested pretty extensively on MacOS, and works fine with the the system supplied Ruby and with self-compiled versions of Ruby. However, the moment it is loaded into Sketchup via the console (i.e. "require 'mymodule'"), Sketchup crashes in the function "st_lookup".

To simplify debugging, I created the standard "hello factorial world" test, and it too crashes sketchup:

factorial.c

int fact(int n) {
 if (n == 0)
 return 1;
 return (n * fact(n-1));
}

factorial.i

%module factorial
int fact(int n);

extconf.rb

require 'mkmf'
create_makefile('factorial')

So nothing fancy. To create the extension, first "swig -ruby factorial.i" is run, followed by "ruby extconf.rb && make". The resulting factorial.bundle file works fine in irb (via "require 'factorial'"). Try to load it in Sketchup via the Ruby Console, and Sketchup crashes with the following backtrace:

Process;         SketchUp [26702]
Path;            /Applications/Google SketchUp 7/SketchUp.app/Contents/MacOS/SketchUp
Identifier;      com.google.sketchupfree7
Version;         SketchUp 7 (7.1.4870)
Code Type;       X86 (Native)
Parent Process;  launchd [117]

Date/Time;       2009-10-04 20;21;46.504 -0400
OS Version;      Mac OS X 10.6.1 (10B504)
Report Version;  6

Interval Since Last Report;          194104 sec
Crashes Since Last Report;           4
Per-App Interval Since Last Report;  686 sec
Per-App Crashes Since Last Report;   2
Anonymous UUID;                      DD7CA090-136F-4294-89AE-7E0032D6E21A

Exception Type;  EXC_CRASH (SIGABRT)
Exception Codes; 0x0000000000000000, 0x0000000000000000
Crashed Thread;  2

Application Specific Information;
abort() called

Thread 0;  Dispatch queue; com.apple.main-thread
0   libruby.1.dylib               	0x1d17f63e st_lookup + 15
1   libruby.1.dylib               	0x1d1542fb rb_intern + 62
2   libruby.1.dylib               	0x1d10b18e rb_define_module + 32
3   factorial.bundle              	0x1a9c9452 Init_factorial + 38 (factorial_wrap.c;1480)
4   com.google.rubyframework      	0x022971a6 dln_load + 285
5   com.google.rubyframework      	0x022ad4c0 rb_require_safe + 623
6   com.google.rubyframework      	0x022ace5d rb_f_require + 35
7   com.google.rubyframework      	0x022a9ca2 call_cfunc + 315
8   com.google.rubyframework      	0x022a90a4 rb_call0 + 1660
9   com.google.rubyframework      	0x022aa83c rb_call + 700
10  com.google.rubyframework      	0x022a2c3d rb_eval + 10073
11  com.google.rubyframework      	0x0229d322 eval_node + 96
12  com.google.rubyframework      	0x022ab60a eval + 1068
13  com.google.rubyframework      	0x0229db8a rb_eval_string + 120
14  com.google.rubyframework      	0x022a8211 rb_protect + 191
15  com.google.rubyframework      	0x0229dbcb rb_eval_string_protect + 42
16  com.google.sketchupfree7      	0x001967f5 0x1000 + 1660917
17  com.google.sketchupfree7      	0x0017f552 0x1000 + 1566034
18  com.google.sketchupfree7      	0x0017f5e2 0x1000 + 1566178
19  com.apple.AppKit              	0x9883d14a -[NSApplication sendAction;to;from;] + 112
20  com.apple.AppKit              	0x9891c891 -[NSControl sendAction;to;] + 108
21  com.apple.AppKit              	0x9899614b -[NSTextField textDidEndEditing;] + 773
22  com.apple.Foundation          	0x935c82fc _nsnote_callback + 345
23  com.apple.CoreFoundation      	0x90fa4c29 __CFXNotificationPost + 905
24  com.apple.CoreFoundation      	0x90fa465a _CFXNotificationPostNotification + 186
25  com.apple.Foundation          	0x935bd120 -[NSNotificationCenter postNotificationName;object;userInfo;] + 128
26  com.apple.AppKit              	0x989f157a -[NSTextView(NSPrivate) _giveUpFirstResponder;] + 553
27  com.apple.AppKit              	0x989f1346 -[NSTextView(NSKeyBindingCommands) insertNewline;] + 531
28  com.apple.AppKit              	0x989f1080 -[NSResponder doCommandBySelector;] + 77
29  com.apple.AppKit              	0x989f0997 -[NSTextView doCommandBySelector;] + 240
30  com.apple.AppKit              	0x989dfa1f -[NSKeyBindingManager(NSKeyBindingManager_MultiClients) interpretEventAsCommand;forClient;] + 1911
31  com.apple.AppKit              	0x989e32bf -[NSTextInputContext handleEvent;] + 1604
32  com.apple.AppKit              	0x989df088 -[NSView interpretKeyEvents;] + 209
33  com.apple.AppKit              	0x989e2b45 -[NSTextView keyDown;] + 751
34  com.apple.AppKit              	0x98914194 -[NSWindow sendEvent;] + 5757
35  com.apple.AppKit              	0x9882cceb -[NSApplication sendEvent;] + 6431
36  com.google.sketchupfree7      	0x00178aa1 0x1000 + 1538721
37  com.apple.AppKit              	0x987c06fb -[NSApplication run] + 917
38  com.apple.AppKit              	0x987b8735 NSApplicationMain + 574
39  com.google.sketchupfree7      	0x00003772 0x1000 + 10098
40  com.google.sketchupfree7      	0x00003699 0x1000 + 9881

I've tried compiling against different versions of Ruby (matching the 1.8.5 that appears to be in Sketchup currently), and even looking through the ruby source at the implementation of "rb_intern" and call to "st_lookup" for inspiration, to no avail. So I'm hoping there's some brilliant developer out there who's figured out what this is all about and can help save my sanity.

Again, any thoughts or tips are appreciated.

Thanks,

Simeon

Google has started deploying products with a tool called Breakpad which detects when a program is about to crash, gathers up debugging information, and allows the user to send it along to Google. This is good from a normal user standpoint, but problematic when trying to debug a native MacOS Ruby extension running inside Sketchup.

Normally on MacOS when a process crashes you get a similar native feature, but the crash report can be reviewed, which I've found helpful in determining where to start debugging. By default, Google Breakpad intercepts this process, and provides no option for reviewing the crash report before it is sent along. After a couple days of frustrating searching about this "feature" I finally figured out how to (partially) reenable the default crash reporter on MacOS, and thought I'd share it here so I didn't feel like all that time spent on it was in vain.

Via the Finder open up Sketchup.app with the "Show Package Contents" option. Navigate through "Contents" and open the "Info.plist" file. Add a new property with name "GoogleBreakpadSendAndExit" with value "NO" (see attached image). Save and restart Sketchup. When Sketchup crashes, you'll still get the Breakpad dialog, but after clicking "Cancel" the default MacOS crash reporter will appear.

I figured this out by reading through the Breakpad source code. More configuration properties are described in Breakpad.h.

I don't know how this works on other platforms, but I suspect some similar options are available.

I hope this helps someone.

Simeon

Best,

Simeon