JSONDecoder Limit

Question

Created Oct ’20

Replies 10

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Views 2.7k

Participants 6

Hello,

I believe I have found a bug in the JSONDecoder. If one tries to decode a JSON object with more than 8 properties, I get an unrecognizable error: "error: Execution was interrupted, reason: EXCBADACCESS (code=1, address=0xe8).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation."
This error happens whenever one executes code similar to below:

Code Block struct Objects: Codable {
  var NAME1: String?
  var NAME2: String?
  var NAME3: String?
  var NAME4: String?
  var NAME5: String?
  var NAME6: String?
  var NAME7: String?
  var NAME8: String?
  var NAME9: String?
}
let NEWDATA = """
[
{
  "NAME1": "hi",
  "NAME2": "hi",
  "NAME3": "hi",
  "NAME4": "hi",
  "NAME5": "hi",
  "NAME6": "hi",
  "NAME7": "hi",
  "NAME8": "hi",
  "NAME9": "HELLO"
}
]
""".data(using: .utf8)!
let decoder2 = JSONDecoder()
  decoder2.dataDecodingStrategy = .deferredToData
  decoder2.keyDecodingStrategy = .convertFromSnakeCase
  let product2 = try decoder2.decode([Objects].self, from: NEWDATA)
  print(product2)

This happens in both the Playground and on the device. Maybe I am doing something wrong but it works when you have only 8 properties in the Objects struct but not when you have 9 or more.

Xcode Version: 12.1
Swift Version: 5.3

Thanks for all your help,

A very frustrated developer

Boost

Answer 1

Claude31 OP

Oct ’20

I tested in playground.

In Xcode 11.3, works OK

In Xcode 12GM, fails with 9 properties, but works if I remove any.

So same observation as yours.

I tested with 12.2 beta:
It works.

So it seems the bug has been corrected.
Please check on your side.

Nevertheless, that should be worth a bug report. Because it is a very serious regression from 11 to 12, and it is important to make sure there are no linked regression remaining in compiler.

Note: don't get frustrated by such a thing, otherwise your developer's life will be nightmarish…

0

Answer 2

Claude31 OP

Oct ’20

Just tested with Xcode 12.1.

Works OK with 9 properties.
Problem is apparently corrected.

0

Answer 3

a3igner OP

Dec ’20

I am using Xcode 12.3 beta on Catalina 10.15.4. and i see the same behaviour in Playground.

A list of 10 properties works fine, but a list of 11 will not run. and wont throw an error.

0

Answer 4

Claude31 OP

Dec ’20

I got a similar error playing in Playground (Xcode 12.2) with the initial data completed to 12 keys.
Error message:
NEWDATA 183 bytes
Playground execution terminated: An error was thrown and was not caught:
▿ DecodingError
▿ dataCorrupted : Context

codingPath : 0 elements
debugDescription : "The given data was not valid JSON."

▿ underlyingError : Optional<Error>

some : Error Domain=NSCocoaErrorDomain Code=3840 "Badly formed object around character 161." UserInfo={NSDebugDescription=Badly formed object around character 161.}

I then realised that I forget the ending comma in NEWDATA after
"NAME9": "HELLO"
Adding it solved the problem.

So I tested with 18 keys and works as well.

0

Answer 5

genjokoan OP

Apr ’21

Problem occurs with Xcode 12.4 (12D4e). Eight properties good, nine properties bad:

Code Block import Foundation
public struct Foo: Codable {
    public let a01: String
    public let a02: String
    public let a03: String
    public let a04: String
    public let a05: String
    public let a06: String
    public let a07: String
    public let a08: String
    public let a09: String
}
let foo = Foo(a01: "foo",
              a02: "foo",
              a03: "foo",
              a04: "foo",
              a05: "foo",
              a06: "foo",
              a07: "foo",
              a08: "foo",
              a09: "foo")
do {
    let encoder = JSONEncoder()
    let data = try encoder.encode(foo)
    if let jsonString = String(data: data, encoding: .utf8) {
        print(jsonString)
    }
} catch {
    print(error)
}

Exception as follows:

Code Block CoderBug.xcplaygroundpage: error: Playground execution aborted: error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=EXC_I386_GPFLT).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.

0

Answer 6

genjokoan OP

Apr ’21

Now believe this is unrelated to JSONDecoder. It is the struct initialisation with nine properties that causes the execution abort.

0

Answer 7

Sabearts OP

Jul ’21

Same kind of problem with Xcode 12.5.1 (12E507). Two nested structures with more than 3 properties and 3 more properties is too much and will throw no error - most of the time. Erratic behavior but extremely disabling.

1

Answer 8

Claude31 OP

Jul ’21

Effectively, just initialising Foo with 9 var crashes Playground. That seems to be a playground problem.

But works OK in an app.

I did file a bug report. FB9393489

2

Answer 9

Claude31 OP

Jul ’21

I just tested in Xcode 13ß4. No more crash. Playground bug is apparently corrected.

1

Answer 10

genjokoan OP

Aug ’21

Apple replied to FB9080056 suggesting reproduce on Xcode 13. Can confirm on beta 4 (13A5201i) as noted by @Claude31 that the defect appears to have been resolved.

0