Files
json/tests/src/fuzzer-parse_json.cpp
T
Niels Lohmann 1649d9eda4 Use and extend the detail helpers to remove duplicated code (#5783)
* Use and extend the detail helpers to remove duplicated code

Library:
- binary_reader: format bytes with hex_byte() instead of snprintf
- add throw_type_must_be() for the 20 copies of type_error.302
- binary_reader: add last_byte_error()/unexpected_byte() for the 32
  "parse error at the last read byte" sites (replaces bon8_error)
- json_sax: add check_container_size() for out_of_range.408 and
  diagnostic_positions::set_container_start/_end()
- json_pointer: add throw_no_parent() (405) and throw_unresolved() (404)

Tests:
- unit-class_parser uses the shared utils::SaxCountdown
- move SaxEventLogger (and its ExitAfter* variants) from unit-class_parser
  and unit-deserialization into the new tests/src/test_sax.hpp

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Factor out more repeated error paths and test boilerplate

Library:
- add throw_cannot_use_with() for the 34 copies of type_error.304-312
  "cannot use X with Y"
- iter_impl: add throw_cannot_get_value() (invalid_iterator.214)
- parser: add syntax_error() for the 12 parse_error.101 sites
- ordered_map: share the four at() bodies via at_impl()
- json_sax_dom_callback_parser: add pop_container() for end_object()
  and end_array()
- binary_reader: build the two UBJSON/BJData length-type messages with
  concat() and last_byte_error()

Tests:
- move same_value(), the NDEBUG guard, and step 0 (parse without
  exceptions) of the seven fuzzer drivers into tests/src/fuzzer_common.hpp

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Name the exception ids and address review comments

Add detail::exception_id, a scoped enum with one named enumerator per
documented exception id, and use it for every id in the library. The
create() functions get an overload for it; the int overloads stay for
user code.

Following the review of #5783: add binary_reader::invalid_byte() and
length_type_error(), basic_json::throw_subscript_wrong_type(), move the
fuzzer includes and the using-declaration into fuzzer_common.hpp, and
rename test_sax.hpp to sax_event_loggers.hpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Silence -Wweak-vtables for the SAX event loggers

The loggers moved from anonymous namespaces in the test files into
sax_event_loggers.hpp, so clang now warns that their vtables are
emitted in every translation unit.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Silence MSVC 2015 C4100 in parser::syntax_error for static SAX::parse_error

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Inline invalid_byte() into its call sites

The wrapper only fixed the message string of unexpected_byte(), which is
the same kind of per-argument helper that was declined for
throw_type_must_be(). Call unexpected_byte("invalid byte", ...) directly.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-11 08:21:13 +02:00

82 lines
2.5 KiB
C++

// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
/*
This file implements a parser test suitable for fuzz testing. Given a byte
array data, it performs the following steps:
- j0 = parse(data, allow_exceptions = false)
- j1 = parse(data)
- assert(j0 is discarded if parsing j1 fails, and j0 == j1 otherwise)
- s1 = serialize(j1)
- j2 = parse(s1)
- s2 = serialize(j2)
- assert(s1 == s2)
The provided function `LLVMFuzzerTestOneInput` can be used in different fuzzer
drivers.
*/
#include "fuzzer_common.hpp"
// see http://llvm.org/docs/LibFuzzer.html
extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
{
// step 0: parse input without exceptions
bool noexcept_threw = false;
json const j_noexcept = parse_without_exceptions([&] { return json::parse(data, data + size, nullptr, false); }, noexcept_threw);
// whether step 1 succeeded; if not, the catch blocks below check that
// step 0 failed, too
bool parsed = false;
try
{
// step 1: parse input
json const j1 = json::parse(data, data + size);
parsed = true;
// without exceptions, the same input must give the same value
assert(!noexcept_threw && !j_noexcept.is_discarded() && same_value(j_noexcept, j1));
try
{
// step 2: round trip
// first serialization
std::string const s1 = j1.dump();
// parse serialization
json const j2 = json::parse(s1);
// second serialization
std::string const s2 = j2.dump();
// serializations must match
assert(s1 == s2);
}
catch (const json::parse_error&)
{
// parsing a JSON serialization must not fail
assert(false);
}
}
catch (const json::parse_error&)
{
// parse errors are ok, because input may be random bytes
assert(parsed || noexcept_threw || j_noexcept.is_discarded());
}
catch (const json::out_of_range&)
{
// out of range errors may happen if provided sizes are excessive
assert(parsed || noexcept_threw || j_noexcept.is_discarded());
}
// return 0 - non-zero return values are reserved for future use
return 0;
}