Use-of-uninitialized-value (OSS-Fuzz issue 347)

[nlohmann]

The library is continuously fuzz tested by Google's OSS-Fuzz. Today, an error was reported:

Detailed report: https://clusterfuzz-external.appspot.com/testcase?key=6240782075822080

Project: json
Fuzzer: libFuzzer_json_fuzzer-parse_msgpack
Fuzz target binary: fuzzer-parse_msgpack
Job Type: libfuzzer_msan_json
Platform Id: linux

Crash Type: Use-of-uninitialized-value
Crash Address: 
Crash State:
std::__1::char_traits<char>::compare
nlohmann::operator==
_start

Recommended Security Severity: Medium


Minimized Testcase (0.25 Kb): https://clusterfuzz-external.appspot.com/download/AMIfv94z1zLLkKnFP000oNMxeOAENBZKbWPmCdd5VTOLC7sRv6D03OH1FiqBTqgDeYAVbeUqki98vM1nXPEMPmIqvCNX43sCp6u-En4GNFxunbHr_DBoJ1eXXhdFO9pmftkYy4wtQQpioimz3cXNQXEg-NfqyRKy77jI6MfFtuGc0K89O20baCOoQ18kz5Hj1y8Q432hDgRZNM_DuStH0zDr_e7xNnXm0SAKNBQME7tpUZMjApnsb9XJu0A8TKefxgdiGe0mvlTocd1nmZ8BX3sYcsfyeoh_y7Dblf9sLZYfgFtJuOPl6du0ZlSEzq5q-xZqGeB_FzPiNz0x65zhOnobut36P-8g29OyV1vJeHCYpUvE-TTHbFEZtZAuFAacJqYoxvjuNtjL?testcase_id=6240782075822080

Issue filed automatically.

See https://github.com/google/oss-fuzz/blob/master/docs/reproducing.md for more information.

This bug is subject to a 90 day disclosure deadline. If 90 days elapse
without an upstream patch, then the bug report will automatically
become visible to the public.

test case: fuzz-3-json_fuzzer-parse_msgpack.zip

==1==WARNING: MemorySanitizer: use-of-uninitialized-value
==1==WARNING: invalid path to external symbolizer!
==1==WARNING: Failed to use and restart external symbolizer!
#0 0x4dc651 in std::__1::char_traits<char>::compare(char const*, char const*, unsigned long) /usr/local/include/c++/v1/__string:211:32
#1 0x49d92f in bool std::__1::operator==<std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) /usr/local/include/c++/v1/string:3510:16
#2 0x49d92f in nlohmann::operator==(nlohmann::basic_json<std::__1::map, std::__1::vector, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, bool, long, unsigned long, double, std::__1::allocator> const&, nlohmann::basic_json<std::__1::map, std::__1::vector, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, bool, long, unsigned long, double, std::__1::allocator> const&) /src/json/src/json.hpp:5567

[nlohmann]

Should be fixed with #405.