program still abort() or exit() with try catch

[mslovy]

I use try catch like below:

while(true) {
          try {
              jsonMsg = json::parse(msg);
          }
          catch(exception& e) {
              ldout << "error message: " << e.what() << endl;
              continue;
          }
}

I expect the program continue to be executed and then processs next msg. but after print out the error message such as parse error. The program abort() or exit(), can anyone give some suggestion about this.

[nlohmann]

Yes, the program should not terminate after catching an exception. What kind of exception did you catch before termination? Do you have a working example?

[mslovy]

I catch the exception parse_error, which means the client send a bad json string so that the proxy cannot decode the json messages.

But I don't want the proxy make a assertion to interrupt its executing, it should be continuing to receive next string message.

[nlohmann]

What does the assertion say?

[mslovy]

like below:

[json.exception.parse_error.101] parse error at line 1, column 84: syntax error while parsing object - une
xpected end of input; expected '}'

[json.exception.parse_error.101] parse error at line 1, column 84: syntax error while parsing object - une
xpected end of input; expected '}'

terminate called after throwing an instance of 'nlohmann::detail::type_error'
what(): [json.exception.type_error.302] type must be string, but is null
Aborted

[nlohmann]

The last exception should not come from the parser. Can you check your debugger where it was thrown?

[mslovy]

yeah, it comes from the message decode,

inline void to_json(nlohmann::json& j, const TapAPIOrderInfo* p) {
17 j = nlohmann::json{
18 {"AccountNo", p->AccountNo},
19 {"ExchangeNo", p->ExchangeNo},
20 {"CommodityType", p->CommodityType},
21 {"CommodityNo", p->CommodityNo},
22 {"ContractNo", p->ContractNo},
23 {"StrikePrice", p->StrikePrice},
24 {"CallOrPutFlag", p->CallOrPutFlag},
25 {"ContractNo2", p->ContractNo2},
26 {"StrikePrice2", p->StrikePrice2},
27 {"CallOrPutFlag2", p->CallOrPutFlag2},
28 {"OrderType", p->OrderType},
29 {"OrderSource", p->OrderSource},
30 {"TimeInForce", p->TimeInForce},
31 {"ExpireTime", p->ExpireTime},
32 {"IsRiskOrder", p->IsRiskOrder}
}

and a null pointer maybe assign to the json.

[nlohmann]

Ok, so that nlohmann::detail::type_error exception is not from the parser. The error message type must be string, but is null means that you try to read a JSON value of type null where a string is expected. This is usually during a from_json conversion. Something like

json j; // null value
std::string s = j; // throws type_error

[mslovy]

got it. but how to deal with parse_error?

[nlohmann]

What do you mean? You already catch it and continue? I am assuming the code of #1541 (comment).

[mslovy]

yeah, but I don't know why the program still exit when the exception occurs.

[nlohmann]

You need to share more information on your code. Originally, you reported a nlohmann::detail::type_error exception, which was thrown outside the code you provided in #1541 (comment).

[nlohmann]

Could you try to catch std::exception &e and output e.what()?

[cosmos33]

i encounter same issue in android platform. same code is fine in mac platform.
this is my code :

try {
std::string testStr = "sfasd23sfwefws";
mJsonObj = nlohmann::json::parse(testStr);
} catch (nlohmann::detail::parse_error &error) {
std::cout << "parse_error" << std::endl;
} catch (nlohmann::detail::exception &error) {
std::cout << "exception" << std::endl;
} catch (std::overflow_error &error) {
std::cout << "overflow_error" << std::endl;
}

this is crash stack in android platform

2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: backtrace:
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #00 pc 0001ce36 /system/lib/libc.so (abort+58)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #1 pc 0007d1d9 /system/lib/libc.so (ifree+880)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #2 pc 0007d2f7 /system/lib/libc.so (je_free+70)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #3 pc 0007ba1b /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libc++_shared.so (std::overflow_error::~overflow_error()+50)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #4 pc 000da765 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (nlohmann::detail::exception::~exception()+32)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #5 pc 000e48a9 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (nlohmann::detail::parse_error::~parse_error()+16)
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #6 pc 000e52ef /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (bool nlohmann::detail::parser<nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator>, bool, long long, unsigned long long, double, std::__ndk1::allocator, nlohmann::adl_serializer>>::sax_parse_internal<nlohmann::detail::json_sax_dom_parser<nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, std::__ndk1::
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #7 pc 000e0107 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (nlohmann::detail::parser<nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator>, bool, long long, unsigned long long, double, std::__ndk1::allocator, nlohmann::adl_serializer>>::parse(bool, nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, std::__ndk1::basic_string<char, std::__ndk1::char_traits,
2019-04-20 14:08:29.584 32581-32581/? A/DEBUG: #8 pc 000ded55 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator>, bool, long long, unsigned long long, double, std::__ndk1::allocator, nlohmann::adl_serializer>::parse(nlohmann::detail::input_adapter&&, std::__ndk1::function<bool (int, nlohmann::detail::parser<nlohmann::basic_json<std::__ndk1::map, std::__ndk1::vector, st
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #9 pc 000fbb6f /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (mmdns::MMDNSJson::MMDNSJson(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator> const&)+434)
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #10 pc 000fb7d3 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (ZNSt6__ndk110shared_ptrIN5mmdns9MMDNSJsonEE11make_sharedIJRNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEEEES3_DpOT+590)
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #11 pc 00122f4d /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (mmdns::MMDNSHttpServerHandle::RequestHttpDNS(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator> const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator> const&)+9468)
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #12 pc 00124ba1 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (mmdns::MMDNSHttpServerHandle::GetCheckResult(std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator> const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits, std::__ndk1::allocator> const&)+72)
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #13 pc 0012816f /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (mmdns::MMDNSServer::RunCheckTask()+1422)
2019-04-20 14:08:29.585 32581-32581/? A/DEBUG: #14 pc 0012d641 /data/app/com.immomo.momo.dev21-xzhU7rJM3enl9mn6NHEkyg==/lib/arm/libmmdns.so (ZNSt6__ndk114__thread_proxyINS_5tupleIJNS_10unique_ptrINS_15__thread_structENS_14default_deleteIS3_EEEEMN5mmdns11MMDNSServerEFvvEPS8_EEEEEPvSD+248)