fix the json parser to handle floats very near overflow

Instead of bounds-testing a double value to guess whether it will overflow,
just convert it to a float and check whether the result is +/- infinity.

PiperOrigin-RevId: 472811865

BUILD

@@ -513,8 +513,22 @@ upb_proto_reflection_library(
 )
 
 cc_test(
-    name = "json_test",
+    name = "json_decode_test",
-    srcs = ["upb/json_test.cc"],
+    srcs = ["upb/json_decode_test.cc"],
+    deps = [
+        ":json",
+        ":json_test_upb_proto",
+        ":json_test_upb_proto_reflection",
+        ":reflection",
+        ":struct_upb_proto",
+        ":upb",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
+    name = "json_encode_test",
+    srcs = ["upb/json_encode_test.cc"],
     deps = [
         ":json",
         ":json_test_upb_proto",

upb/json_decode.c

@@ -745,11 +745,11 @@ static upb_MessageValue jsondec_double(jsondec* d, const upb_FieldDef* f) {
   }
 
   if (upb_FieldDef_CType(f) == kUpb_CType_Float) {
-    if (val.double_val != INFINITY && val.double_val != -INFINITY &&
+    float f = val.double_val;
-        (val.double_val > FLT_MAX || val.double_val < -FLT_MAX)) {
+    if (val.double_val != INFINITY && val.double_val != -INFINITY) {
-      jsondec_err(d, "Float out of range");
+      if (f == INFINITY || f == -INFINITY) jsondec_err(d, "Float out of range");
     }
-    val.float_val = val.double_val;
+    val.float_val = f;
   }
 
   return val;

upb/json_decode_test.cc

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2009-2022, Google LLC
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of Google LLC nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL Google LLC BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "upb/json_decode.h"
+
+#include <stdio.h>
+
+#include "google/protobuf/struct.upb.h"
+#include "gtest/gtest.h"
+#include "upb/def.hpp"
+#include "upb/json_test.upb.h"
+#include "upb/json_test.upbdefs.h"
+#include "upb/upb.hpp"
+
+static upb_test_Box* JsonDecode(const char* json, upb_Arena* a) {
+  upb::Status status;
+  upb::DefPool defpool;
+  upb::MessageDefPtr m(upb_test_Box_getmsgdef(defpool.ptr()));
+  EXPECT_TRUE(m.ptr() != nullptr);
+
+  upb_test_Box* box = upb_test_Box_new(a);
+  int options = 0;
+  bool ok = upb_JsonDecode(json, strlen(json), box, m.ptr(), defpool.ptr(),
+                           options, a, status.ptr());
+  return ok ? box : nullptr;
+}
+
+struct FloatTest {
+  const std::string json;
+  float f;
+};
+
+static const std::vector<FloatTest> FloatTestsPass = {
+    {R"({"f": 0})", 0},
+    {R"({"f": 1})", 1},
+    {R"({"f": 1.000000})", 1},
+    {R"({"f": 1.5e1})", 15},
+    {R"({"f": 15e-1})", 1.5},
+    {R"({"f": -3.5})", -3.5},
+    {R"({"f": 3.402823e38})", 3.402823e38},
+    {R"({"f": -3.402823e38})", -3.402823e38},
+    {R"({"f": 340282346638528859811704183484516925440.0})",
+     340282346638528859811704183484516925440.0},
+    {R"({"f": -340282346638528859811704183484516925440.0})",
+     -340282346638528859811704183484516925440.0},
+};
+
+static const std::vector<FloatTest> FloatTestsFail = {
+    {R"({"f": 1z})", 0},
+    {R"({"f": 3.4028236e+38})", 0},
+    {R"({"f": -3.4028236e+38})", 0},
+};
+
+// Decode some floats.
+TEST(JsonTest, DecodeFloats) {
+  upb::Arena a;
+
+  for (const auto& test : FloatTestsPass) {
+    upb_test_Box* box = JsonDecode(test.json.c_str(), a.ptr());
+    EXPECT_NE(box, nullptr);
+    float f = upb_test_Box_f(box);
+    EXPECT_EQ(f, test.f);
+  }
+
+  for (const auto& test : FloatTestsFail) {
+    upb_test_Box* box = JsonDecode(test.json.c_str(), a.ptr());
+    EXPECT_EQ(box, nullptr);
+  }
+}

upb/json_test.proto

@@ -17,4 +17,6 @@ message Box {
   optional Tag last_tag = 5;
   optional string name = 4;
   optional google.protobuf.Value val = 6;
+  optional float f = 7;
+  optional double d = 8;
 }