[libc] Fix benchmarks build.

libc/utils/benchmarks/CMakeLists.txt

ExternalProject_Add(google-benchmark
     PREFIX google-benchmark
     SOURCE_DIR ${LIBC_SOURCE_DIR}/../llvm/utils/benchmark
     INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}/google-benchmark
     CMAKE_CACHE_ARGS
         -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
         -DCMAKE_C_COMPILER:STRING=${CMAKE_C_COMPILER}
         -DCMAKE_CXX_COMPILER:STRING=${CMAKE_CXX_COMPILER}
         -DCMAKE_CXX_FLAGS:STRING=${GOOGLE_BENCHMARK_TARGET_FLAGS}
+        -DCMAKE_CXX_STANDARD:STRING=14
         -DCMAKE_BUILD_TYPE:STRING=RELEASE
         -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
         -DBENCHMARK_ENABLE_TESTING:BOOL=OFF)
 
 set(GOOGLE_BENCHMARK_LIBC_INSTALL ${CMAKE_CURRENT_BINARY_DIR}/google-benchmark)
 set(GOOGLE_BENCHMARK_LINK_FLAGS    -L${GOOGLE_BENCHMARK_LIBC_INSTALL}/lib/)
 
 #==============================================================================

libc/utils/benchmarks/JSON.cpp

 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/MathExtras.h"
+
 #include <chrono>
 #include <limits>
 #include <memory>
+#include <string>
 #include <vector>
 
 namespace llvm {
 namespace libc_benchmarks {
 
 template <typename T>
 static Error intFromJsonTemplate(const json::Value &V, T &Out) {
   if (const auto &MaybeInt64 = V.getAsInteger()) {
if (auto S = V.getAsNumber()) {
     Out = *S;
     return Error::success();
   }
   return createStringError(errc::io_error, "Can't parse Double");
 }
 
 static Error fromJson(const json::Value &V, std::string &Out) {
   if (auto S = V.getAsString()) {
-    Out = *S;
+    Out = std::string(*S);
     return Error::success();
   }
   return createStringError(errc::io_error, "Can't parse String");
 }
 
 static Error fromJson(const json::Value &V, uint32_t &Out) {
   return intFromJsonTemplate(V, Out);
 }

libc/utils/benchmarks/LibcMemoryBenchmarkMain.cpp

 #include "LibcMemoryBenchmark.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 
+#include <string>
+
 namespace llvm {
 namespace libc_benchmarks {
 
 static cl::opt<std::string>
     Configuration("conf", cl::desc("Specify configuration filename"),
                   cl::value_desc("filename"), cl::init(""));
 
 static cl::opt<std::string> Output("o", cl::desc("Specify output filename"),
#endif
   const auto Runs = S.Configuration.Runs;
   const auto &SR = S.Configuration.Size;
   std::unique_ptr<BenchmarkRunner> Runner = getRunner(S.Configuration);
   const size_t TotalSteps =
       Runner->getFunctionNames().size() * Runs * ((SR.To - SR.From) / SR.Step);
   size_t Steps = 0;
   for (auto FunctionName : Runner->getFunctionNames()) {
     FunctionMeasurements FM;
-    FM.Name = FunctionName;
+    FM.Name = std::string(FunctionName);
     for (size_t Run = 0; Run < Runs; ++Run) {
       for (uint32_t Size = SR.From; Size <= SR.To; Size += SR.Step) {
         const auto Result = Runner->benchmark(S.Options, FunctionName, Size);
         Measurement Measurement;
         Measurement.Runtime = Result.BestGuess;
         Measurement.Size = Size;
         FM.Measurements.push_back(Measurement);
         outs() << format("%3d%% run: %2d / %2d size: %5d ",