fix: accept subnormal doubles when parsing (#1427) (#1695) decodeDouble parsed numbers via `istringstream >> double`. For a subnormal value such as `3.2114e-312`, operator>> sets failbit (the result underflowed) even though it produced the correctly-rounded value. The failure path only special-cased overflow, so subnormals were rejected as "not a number" -- meaning a value jsoncpp had just serialized could fail to parse back. In the failure path, accept the value when it is a subnormal (std::fpclassify(value) == FP_SUBNORMAL). This keys off the value operator>> produces, which is the correctly-rounded subnormal on libstdc++, libc++, and MSVC, so it needs no errno/eof heuristics. It deliberately does not accept results that round to zero, so malformed numbers like "0e" / "0e+" (jsonchecker fail29/fail30) and other junk are still rejected. Applied to both Reader and OurReader. Adds CharReaderTest/parseSubnormal covering subnormals, a writer round-trip, and continued rejection of malformed numbers.
JSON is a lightweight data-interchange format. It can represent numbers, strings, ordered sequences of values, and collections of name/value pairs.
JsonCpp is a C++ library that allows manipulating JSON values, including serialization and deserialization to and from strings. It can also preserve existing comment in deserialization/serialization steps, making it a convenient format to store user input files.
JsonCpp is a mature project in maintenance mode. Our priority is providing a stable, reliable JSON library for the long tail of C++ development.
JsonCpp remains a primary choice for developers who require comment preservation and support for legacy toolchains where modern C++ standards are unavailable. The library is intended to be a reliable dependency that does not require frequent updates or major migration efforts.
1.y.z (master): Actively maintained. Requires C++11.
0.y.z: Legacy support for pre-C++11 compilers. Maintenance is limited to critical security fixes.
00.11.z: Discontinued.
Major versions maintain binary compatibility. Critical security fixes are accepted for both the master and 0.y.z branches.
[!NOTE] Package manager ports (vcpkg, Conan, etc.) are community-maintained. Please report outdated versions or missing generators to their respective repositories.
meson wrap install jsoncpp
For projects requiring a single-header approach, JsonCpp provides a script to generate an amalgamated source and header file.
You can generate the amalgamated files by running the following Python script from the top-level directory:
python3 amalgamate.py
This will generate a dist directory containing jsoncpp.cpp, json/json.h, and json/json-forwards.h. You can then drop these files directly into your project's source tree and compile jsoncpp.cpp alongside your other source files.
Documentation is generated via Doxygen. Additional information is available on the Project Wiki.
JsonCpp is licensed under the MIT license, or public domain where recognized. See LICENSE for details.