Crashlytics log function is crashing in CLSUserLogging.m - crashlytics

Question

Fabric Crashlytics is crashing on calling CLSLogv method occasionally. The crash is very random, not sure on what input it's crashing.
Here is the crash log:
Crashed: com.apple.main-thread
0 CoreFoundation 0x18289d688 __CFStringAppendFormatCore + 12780
1 CoreFoundation 0x18289a464 _CFStringCreateWithFormatAndArgumentsAux2 + 244
2 Foundation 0x1831b6320 -[NSPlaceholderString initWithFormat:locale:arguments:] + 168
3 Dream11 0x1004823e4 CLSLogv (CLSUserLogging.m:368)
4 Dream11 0x1001d73a8 specialized crashlyticsLog(format : String, [CVarArg], file : String, function : String, line : Int) -> () (LogManager.swift)`
Here is the method.
func VERBOSELOG(_ format: String = "",
_ args:[CVarArg] = [],
file: String = #file,
function: String = #function,
line: Int = #line) {
if ENABLED_LOGGING.contains("VERBOSE") {
do {
try crashlyticsLog(format: "\nVERBOSE: " + format, args, file: file, function: function, line: line)
} catch let error {
print(error)
}
}
}
func crashlyticsLog(format: String = "",
_ args:[CVarArg] = [],
file: String = #file,
function: String = #function,
line: Int = #line) throws {
let filename = file.components(separatedBy: "/").last!.components(separatedBy: ".").first!
#if SWIFT_DEBUG
print("\(filename).\(function) line \(line) $ \(format)")
#else
CLSLogv("\(filename).\(function) line \(line) $ \(format)", getVaList(args))
#endif
}

Answer 1

I faced a similar crash, that happened randomly with following stack trace
0 CoreFoundation 0x1b99b84d4 __CFStringAppendFormatCore + 6000
1 CoreFoundation 0x1b99ba5bc _CFStringCreateWithFormatAndArgumentsAux2 + 136
2 flockmail 0x1006725ec CLSLogv + 374 (CLSUserLogging.m:374)
The problem that I later figured out was the way I was logging messages.
CLSLogv(message, getVaList([])) // Incorrect
I was passing message in the format, so if the message had some %#'s or %d's or %0 or similar stuff, then it would look for vaList to replace it.
Fix was
CLSLogv("%#", getVaList([message]))
In you case, it seems format is supplied from outside, just make sure the format string parameter is in sync with args parameter.
Further references :
https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Strings/Articles/FormatStrings.html
https://docs.fabric.io/apple/crashlytics/enhanced-reports.html#custom-logs

Answer 2

Is it the character limit of NSLog, I had the same crash for NSLog and CLSLogv. Not for print