[compiler-rt] [xray] [tests] Detect and handle missing LLVMTestingSupport gracefully

[mgorny]

Summary

Add a code to properly test for presence of LLVMTestingSupport library
when performing a stand-alone build, and skip tests requiring it when
it is not present. Since the library is not installed, llvm-config
reported empty --libs for it and the tests failed to link with undefined
references. Skipping the two fdr_* test files is better than failing to
build, and should be good enough until we find a better solution.

NB: both installing LLVMTestingSupport and building it automatically
from within compiler-rt sources are non-trivial. The former due to
dependency on gtest, the latter due to tight integration with LLVM
source tree.

[dberris]

LGTM

Thanks, @mgorny!

[sgraenitz]

In case compiler-rt abandons llvm-config in favor of find_package(LLVM) one day, we could drop the COMPILER_RT_HAS_LLVMTESTINGSUPPORT logic here and use imported target properties instead. It seems a cleaner solution to me and avoids issues like D57521.

[justinkb]

The check doesn't work correctly if LLVM is built as a dylib and the LLVMTestingSupport static library isn't installed (which it normally wouldn't be)

On my machine llvm-config --components (correctly) doesn't print testingsupport, but since llvm-config --libs "testingsupport" does return "-lLLVM-9" since "If LLVM_LINK_DYLIB is ON, the single shared library will be return for "--libs" (quote from llvm-config source). Since testingsupport never seems to get built into the dylib, we end up with the failing check.

[mgorny]

That sounds like a bug in llvm-config. It shouldn't really return dylib for components that aren't part of it.

[justinkb]

In D55891#1751610, @mgorny wrote:

That sounds like a bug in llvm-config. It shouldn't really return dylib for components that aren't part of it.

I don't disagree. Still, the check is relying on correct behavior the tool apparently doesn't have

[mgorny]

I've tried fixing llvm-config but that's non-trivial. If I fix it to correctly recognize which components are included in dylib, and return other libraries directly, it just uncovers other problems.

Please see if D71613 fixes your problem.

compiler-rt/trunk/cmake/Modules/CompilerRTUtils.cmake

if (LLVM_CONFIG_PATH)
     set(LLVM_LIBRARY_DIR ${LIBRARY_DIR} CACHE PATH "Path to llvm/lib")
     set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
     set(LLVM_TOOLS_BINARY_DIR ${TOOLS_BINARY_DIR} CACHE PATH "Path to llvm/bin")
     set(LLVM_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Paths to LLVM headers")
 
     # Detect if we have the LLVMXRay and TestingSupport library installed and
     # available from llvm-config.
     execute_process(
-      COMMAND ${LLVM_CONFIG_PATH} "--ldflags" "--libs" "xray" "testingsupport"
+      COMMAND ${LLVM_CONFIG_PATH} "--ldflags" "--libs" "xray"
       RESULT_VARIABLE HAD_ERROR
       OUTPUT_VARIABLE CONFIG_OUTPUT)
     if (HAD_ERROR)
       message(WARNING "llvm-config finding xray failed with status ${HAD_ERROR}")
       set(COMPILER_RT_HAS_LLVMXRAY FALSE)
     else()
       string(REGEX REPLACE "[ \t]*[\r\n]+[ \t]*" ";" CONFIG_OUTPUT ${CONFIG_OUTPUT})
       list(GET CONFIG_OUTPUT 0 LDFLAGS)
       list(GET CONFIG_OUTPUT 1 LIBLIST)
       set(LLVM_XRAY_LDFLAGS ${LDFLAGS} CACHE STRING "Linker flags for LLVMXRay library")
       set(LLVM_XRAY_LIBLIST ${LIBLIST} CACHE STRING "Library list for LLVMXRay")
       set(COMPILER_RT_HAS_LLVMXRAY TRUE)
     endif()
 
+    set(COMPILER_RT_HAS_LLVMTESTINGSUPPORT FALSE)
+    execute_process(
+      COMMAND ${LLVM_CONFIG_PATH} "--ldflags" "--libs" "testingsupport"
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE CONFIG_OUTPUT)
+    if (HAD_ERROR)
+      message(WARNING "llvm-config finding testingsupport failed with status ${HAD_ERROR}")
+    else()
+      string(REGEX REPLACE "[ \t]*[\r\n]+[ \t]*" ";" CONFIG_OUTPUT ${CONFIG_OUTPUT})
+      list(GET CONFIG_OUTPUT 0 LDFLAGS)
+      list(GET CONFIG_OUTPUT 1 LIBLIST)
+      if (LIBLIST STREQUAL "")
+        message(WARNING "testingsupport library not installed, some tests will be skipped")
+      else()
+        set(LLVM_TESTINGSUPPORT_LDFLAGS ${LDFLAGS} CACHE STRING "Linker flags for LLVMTestingSupport library")
+        set(LLVM_TESTINGSUPPORT_LIBLIST ${LIBLIST} CACHE STRING "Library list for LLVMTestingSupport")
+        set(COMPILER_RT_HAS_LLVMTESTINGSUPPORT TRUE)
+      endif()
+    endif()
+
     # Make use of LLVM CMake modules.
     # --cmakedir is supported since llvm r291218 (4.0 release)
     execute_process(
       COMMAND ${LLVM_CONFIG_PATH} --cmakedir
       RESULT_VARIABLE HAD_ERROR
       OUTPUT_VARIABLE CONFIG_OUTPUT)
     if(NOT HAD_ERROR)
       string(STRIP "${CONFIG_OUTPUT}" LLVM_CMAKE_PATH_FROM_LLVM_CONFIG)

compiler-rt/trunk/lib/xray/tests/CMakeLists.txt

if (NOT APPLE)
   # Needed by LLVMSupport.
   append_list_if(
     COMPILER_RT_HAS_TERMINFO
     -l${COMPILER_RT_TERMINFO_LIB} XRAY_UNITTEST_LINK_FLAGS)
 
   if (COMPILER_RT_STANDALONE_BUILD)
     append_list_if(COMPILER_RT_HAS_LLVMXRAY ${LLVM_XRAY_LDFLAGS} XRAY_UNITTEST_LINK_FLAGS)
     append_list_if(COMPILER_RT_HAS_LLVMXRAY ${LLVM_XRAY_LIBLIST} XRAY_UNITTEST_LINK_FLAGS)
+    append_list_if(COMPILER_RT_HAS_LLVMTESTINGSUPPORT
+      ${LLVM_TESTINGSUPPORT_LDFLAGS} XRAY_UNITTEST_LINK_FLAGS)
+    append_list_if(COMPILER_RT_HAS_LLVMTESTINGSUPPORT
+      ${LLVM_TESTINGSUPPORT_LIBLIST} XRAY_UNITTEST_LINK_FLAGS)
   else()
     # We add the library directories one at a time in our CFLAGS.
     foreach (DIR ${LLVM_LIBRARY_DIR})
       list(APPEND XRAY_UNITTEST_LINK_FLAGS -L${DIR})
     endforeach()
 
     # We also add the actual libraries to link as dependencies.
     list(APPEND XRAY_UNITTEST_LINK_FLAGS -lLLVMXRay -lLLVMSupport -lLLVMTestingSupport)

compiler-rt/trunk/lib/xray/tests/unit/CMakeLists.txt

-add_xray_unittest(XRayTest SOURCES
+set(TEST_SOURCES
   allocator_test.cc
   buffer_queue_test.cc
-  fdr_controller_test.cc
-  fdr_log_writer_test.cc
   function_call_trie_test.cc
   profile_collector_test.cc
   segmented_array_test.cc
   test_helpers.cc
   xray_unit_test_main.cc)
+
+if (NOT COMPILER_RT_STANDALONE_BUILD OR COMPILER_RT_HAS_LLVMTESTINGSUPPORT)
+  list(APPEND TEST_SOURCES
+    fdr_controller_test.cc
+    fdr_log_writer_test.cc)
+endif()
+
+add_xray_unittest(XRayTest SOURCES ${TEST_SOURCES})