[Openmcl-devel] Trace/BPT trap with cl-opengl loading

Gary Byers gb at clozure.com
Mon Aug 2 03:02:34 UTC 2010

Apple decided to enforce the restriction that some shared libraries (I don't
remember which one(s)) only be initialized on the initial thread of the OS-level
process by executing a breakpoint instruction.  (It's the World's Most Advanced
Operating System!)  That breakpoint causes the process to terminate with the
message you're seeing when the library in question is loaded (directly or as
the result of loading some library which depends on it) from a CCL listener
thread (or a SLIME REPL thread, or ... any thread other than the initial

The general workaround is to replace:

(open-shared-library "culprit.dylib")


   (lambda () (open-shared-library "culprit.dylib")))

There are a few issues:

1) The affected code may be in a third-party lisp library; it'd be good if
    the authors of such libraries made the necessary changes so that people
    didn't keep running into this.

2) It can be hard to know which libraries are affected.  I think that the
    actual check-and-breakpoint is in the initialization code for the
    CoreFoundation library; whether that's correct or not, it's in some
    library that's used by many other things on OSX, so the rule of thumb
    is something like "when in doubt, force library loading to happen on
    the initial thread  in OSX."

3) There are several ways to do what I'm calling
    RUN-IN-INITIAL-THREAD-AND-WAIT-UNTIL-DONE; I don't think that we yet
    offer a standard way of doing this (though CCL::CALL-IN-INITIAL-PROCESS
    us present in recent versions of the trunk and is intended to become
    an exported/documented/standard interface in the near future.)

    We changed some of our examples when this "check and breakpoint" behavior
    was introduced (in 10.6, IIRC); see "ccl:examples;opengl-ffi.lisp", for

4) I'd want to think about this more than I have, but at the moment I can't
    think of a reason for OPEN-SHARED-LIBRARY not to at least default to
    doing what it does on the initial thread by default.

On Sun, 1 Aug 2010, Kevin Smith wrote:

> The only hurdle for me for trying out (and maybe switching) to clozure on the mac platform is that I can't seem to get the
> cl-opengl package loaded.  I get the error:  "Trace/BPT trap" when I try to load that package.  (All other dependent packages
> like cffi, loaded successfully).
> I am using ccl64,  version 1.5 on Darwin/MAC OS  (DarwinX8664).  Latest version of cl-opengl.
> I believe I also tried it on the 32-bit ccl.  Same problem.  It looks like it only compiles a few source files in the
> cl-opengl package before it dies.
> If someone can point out to me how I can trace this to provide more information on where it is crashing or maybe someone has
> run across this already with this particular package.
> Thanks,
> Kevin

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