[Libomptarget] Pass '-Werror=global-constructors' to the libomptarget build

Summary:
A runtime library should not have global constructors. This has caused
many issues in the past so we would make them a hard error if they show
up. This required rewriting the RecordReplay implementation because it
uses a SmallVector internally which can't be made constexpr.

Author: jhuber6

openmp/libomptarget/CMakeLists.txt

@@ -36,6 +36,8 @@ include(LibomptargetUtils)
 # Get dependencies for the different components of the project.
 include(LibomptargetGetDependencies)
 
+check_cxx_compiler_flag(-Werror=global-constructors OFFLOAD_HAVE_WERROR_CTOR)
+
 # LLVM source tree is required at build time for libomptarget
 if (NOT LIBOMPTARGET_LLVM_INCLUDE_DIRS)
   message(FATAL_ERROR "Missing definition for LIBOMPTARGET_LLVM_INCLUDE_DIRS")
@@ -82,6 +84,9 @@ set(offload_compile_flags -fno-exceptions)
 if(NOT LLVM_ENABLE_RTTI)
   set(offload_compile_flags ${offload_compile_flags} -fno-rtti)
 endif()
+if(OFFLOAD_HAVE_WERROR_CTOR)
+  list(APPEND offload_compile_flags -Werror=global-constructors)
+endif()
 
 # TODO: Consider enabling LTO by default if supported.
 # https://cmake.org/cmake/help/latest/module/CheckIPOSupported.html can be used

openmp/libomptarget/tools/kernelreplay/llvm-omp-kernel-replay.cpp

@@ -23,6 +23,9 @@
 
 using namespace llvm;
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wglobal-constructors"
+
 cl::OptionCategory ReplayOptions("llvm-omp-kernel-replay Options");
 
 // InputFilename - The filename to read the json description of the kernel.
@@ -52,6 +55,8 @@ static cl::opt<unsigned> NumThreadsOpt("num-threads",
 static cl::opt<int32_t> DeviceIdOpt("device-id", cl::desc("Set the device id."),
                                     cl::init(-1), cl::cat(ReplayOptions));
 
+#pragma GCC diagnostic pop
+
 int main(int argc, char **argv) {
   cl::HideUnrelatedOptions(ReplayOptions);
   cl::ParseCommandLineOptions(argc, argv, "llvm-omp-kernel-replay\n");