json error on parsing DBL_MAX from string

[sinannuman]

Hello,
I am facing an exception with serialization on QNX platform. I am serializing a double with the DBL_MAX value (1.7976931348623157e+308). Then I try to parse that value from the string but the exception is thrown:

Code snippet is:

{
    try
    {
        double d = DBL_MAX;
        nlohmann::json js;
        js["max"] = d;
 
        std::stringstream ss;
        ss << js["max"].dump();
        std::cerr << ss.str() << std::endl;
        nlohmann::json js2 = nlohmann::json::parse(ss.str());
        std::cerr << js2.dump() << std::endl;
    }
    catch(const std::exception& e)
    {
        std::cerr << e.what() << '\n';
    }
}  

Exception:
[json.exception.out_of_range.406] number overflow parsing '1.7976931348623157e+308'

Related ticket:
#360

[t-b]

@sinannuman Do the tests pass on your platform?

If I read the test code correctly we already have a test for DBL_MAX, see

json/test/src/unit-regression.cpp

Lines 705 to 725 in ed55414

	SECTION("issue #360 - Loss of precision when serializing <double>")
	{
	auto check_roundtrip = [](double number)
	{
	CAPTURE(number)
	json j = number;
	CHECK(j.is_number_float());
	std::stringstream ss;
	ss << j;
	CHECK_NOTHROW(ss >> j);
	CHECK(j.is_number_float());
	CHECK(j.get<json::number_float_t>() == number);
	};
	check_roundtrip(100000000000.1236);
	check_roundtrip((std::numeric_limits<json::number_float_t>::max)());
	// Some more numbers which fail to roundtrip when serialized with digits10 significand digits (instead of max_digits10)

.

[nlohmann]

I cannot reproduce the issue (macOS 10.14.6, Xcode 11.0):

#include <iostream>
#include <sstream>
#include <cfloat>
#include "json.hpp"

using json = nlohmann::json;

int main() {
    try
    {
        double d = DBL_MAX;
        nlohmann::json js;
        js["max"] = d;
 
        std::stringstream ss;
        ss << js["max"].dump();
        std::cerr << ss.str() << std::endl;
        nlohmann::json js2 = nlohmann::json::parse(ss.str());
        std::cerr << js2.dump() << std::endl;
    }
    catch(const std::exception& e)
    {
        std::cerr << e.what() << '\n';
    }
}

Output:

1.7976931348623157e+308
1.7976931348623157e+308
Program ended with exit code: 0