'Undefined symbol' at runtime (ArchLinux)

[vitaminwater]

Hi,

Got a small issue when installing WiringPi-Ruby, all compilation and gem installation went well (except the include path to the WiringPi headers were wrong (?)).
But when I tried running it I got 'Undefined symbol' for wiringPiSetup, after checking with nm,
none of the WiringPi functions were "linked" inside the .so.
But all this seems "normal" as neither the Makefile nor any other files have anything related to libwiringpi.a;
which makes me think that I've done something wrong...

I ended up modifying the Makefile created by ruby :/ to explicitly link to libwiringpi..
Looks like everything works now, but I still feel like something is wrong :/

Thanks for your work !

[samwho]

I'm getting a similar error but under slightly different circumstances.

I've forked this repository in order to clean up the Ruby code a bit (no offence meant, it's just too un-rubyish for me ^_^). I'm creating a Rakefile at the moment to help with building all of the external dependencies, generate the Makefile, generate the wiringpi_wrap.c file using SWIG and so on. It all appears to work fine until I install the gem on my Pi and get this error:

ruby: symbol lookup error: /home/sam/.rvm/gems/ruby-1.9.3p194@wiringpi_test/gems/wiringpi-1.1.0/lib/wiringpi/wiringpi.so: undefined symbol: wiringPiSetup

I, too, am on Arch Linux (both on my Pi and on my dev machine). The interesting bit about this is when I gem install from RubyGems and get your original version it works fine, no problems at all. So I can only conclude that I've broken something :)

@vitaminwater it would be greatly appreciated if you could tell me what part of the Makefile to edited to properly link the wiringpi.so file. I'm very new to native Ruby extensions and .so files in general ^_^

You can view my current code base here: https://github.com/samwho/WiringPi-Ruby/tree/sam-develop. Hopefully you can see where I've gone wrong. I really want to hack on this library and make it a brilliant way to interact with the GPIO pins in an idiomatic Ruby way.

[vitaminwater]

Well, my solution is really "trash" not the type of things you like to show;), I only wanted to compile and try:)

First you have to locate the Makefile generated by gem (when typing 'gem build'), like :

~/.gem/ruby/1.9.1/gems/wiringpi-1.1.0/ext/wiringpi/Makefile

at line 75 you have the declaration of the variable ldflags :

ldflags = blablalbla

just add at the end of this line :

-L/usr/local/lib/ -lwiringPi

/usr/local/lib is where libwiringPi.a is.

Once done, re-compile with a :

make clean;make;

copy the wiringpi.so to ../../lib/wiringpi/wiringpi.so (relative to the new one).

And here you go... that's clearly not how it should be fixed, but who waits to find the right solution when you just received your brand new raspi;) ???

[samwho]

Yeah, your fix worked for me @vitaminwater :) I did it a little differently but it was, in essence, the same. The problem is indeed that libwiringPi.a isn't being linked. I didn't have it installed on my system, so the first thing I did was:

$ cd ext/wiringpi/WiringPi/wiringPi/
$ make
$ sudo make install

If I didn't do this I'd get a compile time error telling me wiringPi doesn't exist. Then I edited the Makefile so that line 117 looked like this:

LIBS = $(LIBRUBYARG_SHARED)  -lpthread -lrt -ldl -lcrypt -lm   -lc -lwiringPi

Which is a minor diversion from the solution above but it worked all the same. Doing the standard compile instructions for the ext/wiringpi/ directory worked fine and the new ext/wiringpi/wiringpi.so symbol table looked correct under nm -g ext/wiringpi/wiringpi.so.

Then it was just a case of moving the new .so into the correct location as detailed above and things worked.

The Makefile that extconf.rb generates needs tweaking for this build process to work correctly it seems :/