[flang-rt] For variant, add abort entry for OMP_OFFLOAD_BUILD (llvm#3263)

Author: ronlieb

flang-rt/lib/runtime/CMakeLists.txt

@@ -12,6 +12,8 @@ find_package(Backtrace)
 set(HAVE_BACKTRACE ${Backtrace_FOUND})
 set(BACKTRACE_HEADER ${Backtrace_HEADER})
 
+# set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
+
 # List of files that are buildable for all devices.
 set(supported_sources
   ${FLANG_SOURCE_DIR}/lib/Decimal/binary-to-decimal.cpp

flang-rt/lib/runtime/assign.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "flang/Runtime/assign.h"
+#include "flang/Runtime/stop.h"
 #include "flang-rt/runtime/assign-impl.h"
 #include "flang-rt/runtime/derived.h"
 #include "flang-rt/runtime/descriptor.h"
@@ -834,6 +835,17 @@ void RTDEF(AssignPolymorphic)(Descriptor &to, const Descriptor &from,
           PolymorphicLHS);
 }
 
+#if defined(OMP_OFFLOAD_BUILD)
+// To support a recently added use of variant in the OpenMP offload build,
+// added an abort wrapper which calls the flang-rt FortranAAbort.
+// Avoids the following linker error:
+//   ld.lld: error: undefined symbol: abort
+//   >>> referenced by /tmp/device_aassign.amdgcn.gfx90a-34a7ed.img.lto.o:(std::__throw_bad_variant_access(char const*))
+extern "C" void abort(void) {
+  RTNAME(Abort)();
+}
+#endif
+
 RT_EXT_API_GROUP_END
 } // extern "C"
 } // namespace Fortran::runtime