Write LOG(WARNING) to stderr by default

PiperOrigin-RevId: 737663723
Change-Id: Ifdfb843bc4d3770fe201561587d2936a8bb10684

Author: andreas-abel

fleetbench/BUILD

@@ -109,9 +109,12 @@ cc_library(
         ":dynamic_registrar",
         ":maybe_llvmlibc",
         "//fleetbench/common",
+        "@com_google_absl//absl/base:log_severity",
         "@com_google_absl//absl/flags:parse",
         "@com_google_absl//absl/log",
         "@com_google_absl//absl/log:check",
+        "@com_google_absl//absl/log:globals",
+        "@com_google_absl//absl/log:initialize",
         "@com_google_benchmark//:benchmark",
         "@com_google_tcmalloc//tcmalloc:malloc_extension",
         "@libnuma//:numa",

fleetbench/benchmark_main.cc

@@ -19,9 +19,12 @@
 #include <thread>
 #include <vector>
 
+#include "absl/base/log_severity.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/parse.h"
 #include "absl/log/check.h"
+#include "absl/log/globals.h"
+#include "absl/log/initialize.h"
 #include "absl/log/log.h"
 #include "benchmark/benchmark.h"
 #include "fleetbench/common/common.h"
@@ -38,12 +41,16 @@ ABSL_FLAG(bool, prevent_numa_migrations, true,
 int main(int argc, char* argv[]) {
   benchmark::Initialize(&argc, argv);
   absl::ParseCommandLine(argc, argv);
+  absl::InitializeLog();
   static auto* background ABSL_ATTRIBUTE_UNUSED =
     tcmalloc::MallocExtension::NeedsProcessBackgroundActions() ?
     new std::thread([]() {
       tcmalloc::MallocExtension::ProcessBackgroundActions();
     }) : nullptr;
 
+  // Print warnings to stderr.
+  absl::SetStderrThreshold(absl::LogSeverityAtLeast::kWarning);
+
   if (absl::GetFlag(FLAGS_prevent_numa_migrations) && numa_available() != -1) {
     // Set the CPU affinity to the intersection of the current affinity and the
     // CPUs in the current NUMA node.