fix more warnings

Author: dmah42

include/benchmark/benchmark.h

@@ -1304,7 +1304,7 @@ class BENCHMARK_EXPORT Benchmark {
  public:
   const char* GetName() const;
   int ArgsCnt() const;
-  const char* GetArgName(size_t arg) const;
+  const char* GetArgName(int arg) const;
 
  private:
   friend class BenchmarkFamilies;

src/benchmark_register.cc

@@ -480,9 +480,11 @@ int Benchmark::ArgsCnt() const {
   return static_cast<int>(args_.front().size());
 }
 
-const char* Benchmark::GetArgName(size_t arg) const {
-  BM_CHECK_LT(arg, arg_names_.size());
-  return arg_names_[arg].c_str();
+const char* Benchmark::GetArgName(int arg) const {
+  BM_CHECK_GE(arg, 0);
+  size_t uarg = static_cast<size_t>(arg);
+  BM_CHECK_LT(uarg, arg_names_.size());
+  return arg_names_[uarg].c_str();
 }
 
 TimeUnit Benchmark::GetTimeUnit() const {

test/benchmark_gtest.cc

@@ -38,7 +38,7 @@ TEST(AddRangeTest, Advanced64) {
 
 TEST(AddRangeTest, FullRange8) {
   std::vector<int8_t> dst;
-  AddRange(&dst, int8_t{1}, std::numeric_limits<int8_t>::max(), int8_t{8});
+  AddRange(&dst, int8_t{1}, std::numeric_limits<int8_t>::max(), 8);
   EXPECT_THAT(
       dst, testing::ElementsAre(int8_t{1}, int8_t{8}, int8_t{64}, int8_t{127}));
 }