XXX: not-working std::strtod for xref to https://codereview.chromium.org/2044643005/

base/strings/string_number_conversions_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/strings/string_number_conversions.h"
 
 #include <errno.h>
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
@@ skipping 787 matching lines @@
 }
 
 TEST(StringNumberConversionsTest, HexEncode) {
   std::string hex(HexEncode(NULL, 0));
   EXPECT_EQ(hex.length(), 0U);
   unsigned char bytes[] = {0x01, 0xff, 0x02, 0xfe, 0x03, 0x80, 0x81};
   hex = HexEncode(bytes, sizeof(bytes));
   EXPECT_EQ(hex.compare("01FF02FE038081"), 0);
 }
 
+uint64_t RawFP(double fp) {
+  return *reinterpret_cast<uint64_t*>(&fp);
+}
+
+// Test cases of known-bad strtod conversions that motivated the use of dmg_fp.
+// See https://bugs.chromium.org/p/chromium/issues/detail?id=593512.
+TEST(StringNumberConversionsTest, StrtodFailures) {
+  static const struct {
+    const char* input;
+    uint64_t expected;
+  } cases[] = {
+      // http://www.exploringbinary.com/incorrectly-rounded-conversions-in-visual-c-plus-plus/
+      {"9214843084008499", 0x43405e6cec57761aULL},
+      {"0.500000000000000166533453693773481063544750213623046875",
+       0x3fe0000000000002ULL},
+      {"30078505129381147446200", 0x44997a3c7271b021ULL},
+      {"1777820000000000000001", 0x4458180d5bad2e3eULL},
+      {"0.500000000000000166547006220929549868969843373633921146392822265625",
+       0x3fe0000000000002ULL},
+      {"0.50000000000000016656055874808561867439493653364479541778564453125",
+       0x3fe0000000000002ULL},
+      {"0.3932922657273", 0x3fd92bb352c4623aULL},
+
+      // http://www.exploringbinary.com/incorrectly-rounded-conversions-in-gcc-and-glibc/
+      {"0.500000000000000166533453693773481063544750213623046875",
+       0x3fe0000000000002ULL},
+      {"3.518437208883201171875e13", 0x42c0000000000002ULL},
+      {"62.5364939768271845828", 0x404f44abd5aa7ca4ULL},
+      {"8.10109172351e-10", 0x3e0bd5cbaef0fd0cULL},
+      {"1.50000000000000011102230246251565404236316680908203125",
+       0x3ff8000000000000ULL},
+      {"9007199254740991.4999999999999999999999999999999995",
+       0x433fffffffffffffULL},
+
+      // http://www.exploringbinary.com/incorrect-decimal-to-floating-point-conversion-in-sqlite/
+      {"1e-23", 0x3b282db34012b251ULL},
+      {"8.533e+68", 0x4e3fa69165a8eea2ULL},
+      {"4.1006e-184", 0x19dbe0d1c7ea60c9ULL},
+      {"9.998e+307", 0x7fe1cc0a350ca87bULL},
+      {"9.9538452227e-280", 0x0602117ae45cde43ULL},
+      {"6.47660115e-260", 0x0a1fdd9e333badadULL},
+      {"7.4e+47", 0x49e033d7eca0adefULL},
+      {"5.92e+48", 0x4a1033d7eca0adefULL},
+      {"7.35e+66", 0x4dd172b70eababa9ULL},
+      {"8.32116e+55", 0x4b8b2628393e02cdULL},
+  };
+
+  for (const auto& test : cases) {
+    double output;
+    EXPECT_TRUE(StringToDouble(test.input, &output));
+    EXPECT_EQ(RawFP(output), test.expected);
+  }
+}
+
 }  // namespace base