I’ve been working a little bit on the ruby-llvm project (Ruby bindings for LLVM using Ruby-FFI)–mainly adding tests to the already existing functionality–and so had to build LLVM as a shared library.
Building LLV as a shared library on most platforms is trivial. It’s just a matter of enabling a flag on the configure phase of the build.
./configure --enabled-shared
I actually use brew to build it, but the principle is the same:
brew install llvm --shared
However, just building it like this on Mac OS X 10.6 results in the following errors when loading the library on Ruby-FFI:
dyld: loaded: /Users/<user>/llvm/2.8/lib/libLLVM-2.8.dylib
dyld: lazy symbol binding failed: Symbol not found:
__ZN4llvm2cl6Option11addArgumentEv
Referenced from: /Users/<user>/llvm/2.8/lib/libLLVM-2.8.dylib
Expected in: flat namespace
dyld: Symbol not found: __ZN4llvm2cl6Option11addArgumentEv
Referenced from: /Users/<user>/llvm/2.8/lib/libLLVM-2.8.dylib
Expected in: flat namespace
Trace/BPT trap
After some investigation and an e-mail exchange with Takanori Ishikawa, I arrived at the following patch which solves the problem and allows LLVM to load cleanly as a shared library:
diff --git a/Makefile.rules b/Makefile.rules
index 9cff105..44d5b2d 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -497,7 +497,7 @@ ifeq ($(HOST_OS),Darwin)
# Get "4" out of 10.4 for later pieces in the makefile.
DARWIN_MAJVERS := $(shell echo $(DARWIN_VERSION)| sed -E
's/10.([0-9]).*/\1/')
- SharedLinkOptions=-Wl,-flat_namespace -Wl,-undefined,suppress \
+ SharedLinkOptions=-Wl,-undefined,dynamic_lookup \
-dynamiclib
ifneq ($(ARCH),ARM)
SharedLinkOptions += -mmacosx-version-min=$(DARWIN_VERSION)
The options above use the default two-level namespace on OS X and change name resolution to run-time resolution.
Using those options doesn’t seem to have any ill effects but I’m curious why LLVM doesn’t do that already, especially considering many other dynamic libraries for Mac OS X are compiled using the new options specified above. In fact, the former options actually seem to be remnants from pre-10.3 days. Just in case, I’ve asked that very question on the LLVM-dev mailing list.
Meanwhile, the patch works for me. I also made available a modified version for brew. YMMV.