[LLVMdev] Optimized "opt" on Darwin fails to load dynamic libraries with passes

[Harel Cain]

Hi again everyone,

A year ago I asked about this problem which has been reported by me and a
few others. I'm basically repeating the same problem report below because
neither I nor the others who raised this issue got any response.

http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-December/036764.html
http://lists.cs.uiuc.edu/pipermail/llvmdev/2010-November/036289.html

This is a problem that occurs only on Darwin (MacOS) and not on Linux.

When llvm 2.9 is compiled with ENABLE_OPTIMIZED=1, the "opt" tool fails to
load LLVM passes in dynamic libraries (.dylib) files, regardless of how
they themselves were built. When opt is built with ENABLE_OPTIMIZED=0, all
is well.

Here is some informative output with my comments.
Seems to me the problem is in stripping the symbols of the
assignPassManager virtual method from the various subclasses of llvm::Pass.

// the release version has all the necessary symbols in place *before it is
installed to /usr/local/bin*&
$ nm -m Release+Asserts/bin/opt | grep assignPass
000000010042b7c0 (__TEXT,__text) external
__ZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001002a27c0 (__TEXT,__text) external
__ZN4llvm10RegionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
000000010042b490 (__TEXT,__text) external
__ZN4llvm12FunctionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
000000010042b260 (__TEXT,__text) external
__ZN4llvm14BasicBlockPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001002053a0 (__TEXT,__text) external
__ZN4llvm16CallGraphSCCPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001004223d0 (__TEXT,__text) weak external
__ZN4llvm4Pass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
0000000100262120 (__TEXT,__text) external
__ZN4llvm8LoopPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001004d7936 (__TEXT,__cstring) non-external
__ZZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004bcf42 (__TEXT,__cstring) non-external
__ZZN4llvm10RegionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004d7924 (__TEXT,__cstring) non-external
__ZZN4llvm12FunctionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004d7901 (__TEXT,__cstring) non-external
__ZZN4llvm14BasicBlockPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004b404f (__TEXT,__cstring) non-external
__ZZN4llvm16CallGraphSCCPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004b9ce0 (__TEXT,__cstring) non-external
__ZZN4llvm8LoopPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__

// same is true for the debug build
$ nm -m Debug+Asserts/bin/opt | grep assignPass
000000010040ea82 (__TEXT,__text) external
__ZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
0000000100299a82 (__TEXT,__text) external
__ZN4llvm10RegionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
000000010040e8a0 (__TEXT,__text) external
__ZN4llvm12FunctionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
000000010040e758 (__TEXT,__text) external
__ZN4llvm14BasicBlockPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001001fcb5e (__TEXT,__text) external
__ZN4llvm16CallGraphSCCPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001004093a8 (__TEXT,__text) weak external
__ZN4llvm4Pass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
000000010025687e (__TEXT,__text) external
__ZN4llvm8LoopPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
00000001004e349b (__TEXT,__cstring) non-external
__ZZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004c8414 (__TEXT,__cstring) non-external
__ZZN4llvm10RegionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004e3489 (__TEXT,__cstring) non-external
__ZZN4llvm12FunctionPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004e3466 (__TEXT,__cstring) non-external
__ZZN4llvm14BasicBlockPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004bf4e6 (__TEXT,__cstring) non-external
__ZZN4llvm16CallGraphSCCPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__
00000001004c5402 (__TEXT,__cstring) non-external
__ZZN4llvm8LoopPass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeEE8__func__

// however, once it is installed with "make install" to /usr/local/bin,
it's stripped of most of the relevant symbols (those of the llvm::Pass
subclasses)
$ nm -m /usr/local/bin/opt | grep assignPass
00000001004223d0 (__TEXT,__text) weak external
__ZN4llvm4Pass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE

// my dynamic library contains a ModulePass, with a matching symbol that is
missing in the installed "opt" binary
$ nm -m /usr/local/lib/libMyPass.dylib | grep assignPass
         (undefined) external
__ZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE

// and indeed, when opt tries to load it, it fails.
$ opt -load /usr/local/lib/libMyPass.dylib
Error opening '/usr/local/lib/libMyPass.dylib':
dlopen(/usr/local/lib/libMyPass.dylib, 9): Symbol not found:
__ZN4llvm10ModulePass17assignPassManagerERNS_7PMStackENS_15PassManagerTypeE
  Referenced from: /usr/local/lib/libMyPass.dylib
  Expected in: flat namespace
 in /usr/local/lib/libMyPass.dylib
  -load request ignored.


Thanks a lot,

Harel Cain

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