[lit] Don't set DYLD_LIBRARY_PATH when DYLD_INSERT_LIBRARIES is set.

[JDevlieghere]

Summary

Setting DYLD_INSERT_LIBRARIES to the Asan runtime and DYLD_LIBRARY_PATH to the LLVM shared library dir causes the test suite to crash with a segfault. We see this on the LLDB sanitized bot [1] on GreenDragon. I've spent some time investigating, but I'm not sure what's going on (yet).

Originally I thought this was because we were building compiler-rt and were loading an incompatible, just-built Asan library. However, the issue persists even without compiler-rt. It doesn't look like the Asan runtime is opening any other libraries that might be found in LLVM's shared library dir and talking to the team confirms that. Another possible explanation is that we're loading lldb form a place we don't expect, but that doesn't make sense either, because DYLD_LIBRARY_PATH is always set without the crash. I tried different Python versions and interpreters but the issue persist.

As a (temporary?) workaround I propose not setting DYLD_LIBRARY_PATH when DYLD_INSERT_LIBRARIES is set so we can turn the Asan bot on again and get useful results.

[1] http://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake-sanitized/

[aprantl]

It's a hack, but it's a well-documented one.

lldb/trunk/lit/Suite/lit.cfg

if 'Address' in config.llvm_use_sanitizer:
   if 'Darwin' in config.host_os and 'x86' in config.host_triple:
     import subprocess
     resource_dir = subprocess.check_output(
         [config.cmake_cxx_compiler, '-print-resource-dir']).strip()
     runtime = os.path.join(resource_dir, 'lib', 'darwin',
                            'libclang_rt.asan_osx_dynamic.dylib')
     config.environment['DYLD_INSERT_LIBRARIES'] = runtime
 
-# Shared library build of LLVM may require LD_LIBRARY_PATH or equivalent.
 def find_shlibpath_var():
   if platform.system() in ['Linux', 'FreeBSD', 'NetBSD', 'SunOS']:
     yield 'LD_LIBRARY_PATH'
   elif platform.system() == 'Darwin':
     yield 'DYLD_LIBRARY_PATH'
   elif platform.system() == 'Windows':
     yield 'PATH'
 
+if not config.environment['DYLD_INSERT_LIBRARIES']:
+  # Shared library build of LLVM may require LD_LIBRARY_PATH or equivalent.
+  # This clashes with DYLD_INSERT_LIBRARIES which is needed on Darwin.
   for shlibpath_var in find_shlibpath_var():
-  # In stand-alone build llvm_shlib_dir specifies LLDB's lib directory
-  # while llvm_libs_dir specifies LLVM's lib directory.
+    # In stand-alone build llvm_shlib_dir specifies LLDB's lib directory while
+    # llvm_libs_dir specifies LLVM's lib directory.
     shlibpath = os.path.pathsep.join(
       (config.llvm_shlib_dir,
       config.llvm_libs_dir,
       config.environment.get(shlibpath_var, '')))
     config.environment[shlibpath_var] = shlibpath
     break
   else:
     lit_config.warning("unable to inject shared library path on '{}'"
                       .format(platform.system()))
 
 # Build dotest command.
 dotest_cmd = [config.dotest_path, '-q']
 dotest_cmd.extend(config.dotest_args_str.split(';'))
 
 # We don't want to force users passing arguments to lit to use `;` as a
 # separator. We use Python's simple lexical analyzer to turn the args into a
 # list.