I am trying to perform some debugging using LLDB on a buggy code:
#IBAction func somePrettyAction(sender: AnyObject) {
let names = ["LLDB", "is", "fun", "Kudos :)"]
println("out of index name: \(names[5])")
}
So when app crashed at println (for obvious reasons ;)), I typed -'Thread Info' at XCode debugger console, and it gave me below output:
thread #1: tid = 0x6fbc, 0x000000010ee5f1d0 libswiftCore.dylib`Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.UInt) -> () + 160, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
but when I typed - 't i', it showed below message:
error: invalid thread #i.
As per related wwdc video short form of given command should work, but for some reasons it is not working, any ideas?
Yeah, I noticed that too. The presentation is incorrect. That's not the abbreviation for thread info. A suitable abbreviation now is th i.
Using t is the abbreviation for thread select. Thus, t 2 is equivalent to thread select 2.
Type help at the (lldb) prompt, and it will show you a list of the current abbreviations.
Related
I'm debugging v8 using lldb.
How can I print the string inside of Handle<String> Source?
The debug process is as follows:
(lldb) r
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 2.1
frame #0: 0x000000010100536b libv8.dylib`v8::internal::Compiler::GetSharedFunctionInfoForScript(isolate=0x0000000118008000, source=Handle<v8::internal::String> # 0x00007ffeefbfd4a0, script_details=0x00007ffeefbfd730, origin_options=(flags_ = 0), extension=0x0000000000000000, cached_data=0x0000000000000000, compile_options=kNoCompileOptions, no_cache_reason=kNoCacheNoReason, natives=NOT_NATIVES_CODE) at compiler.cc:2806:27
2803 MaybeHandle<SharedFunctionInfo> Compiler::GetSharedFunctionInfoForScript(
2804 solate* isolate, Handle<String> source,
2805 ScriptCompiler::NoCacheReason no_cache_reason, NativesFlag natives) {
-> 2806 ScriptCompileTimerScope compile_timer(isolate, no_cache_reason);
2807
2808 if (compile_options == ScriptCompiler::kNoCompileOptions ||
2809 compile_options == ScriptCompiler::kEagerCompile) {
Target 0: (d8) stopped.
(lldb) p source
(v8::internal::Handle<v8::internal::String>) $9 = {
v8::internal::HandleBase = {
location_ = 0x000000010f009a60
}
}
(lldb) p *$9
(v8::internal::String) $10 = {
v8::internal::TorqueGeneratedString<v8::internal::String, v8::internal::Name> = {
.....
}
}
Take a look at tools/lldb_commands.py. In short: configure your LLDB to load that script:
echo "command script import /path/to/v8/tools/lldb_commands.py" >> ~/.lldbinit
and then use the convenience commands it provides, the most important one being job, a mnemonic for "JavaScript object". It needs the raw pointer value that you'll see as ptr_ = ... somewhere in the output of p *$9, but you don't need to retrieve it manually. Example:
(lldb) job source->ptr_
0x28c008109019: [String]: "console.log('hello world');"
(Side note: tools/gdbinit tends to have a few more features than tools/lldbinit, because most folks on the team use GDB. We'd be happy to accept patches to improve LLDB support; relevant to the case at hand would be gdbinit's jh shortcut (allowing simply jh source) that currently has no equivalent in lldbinit.)
Issue
Following is a minimal, contrived example:
read :: FilePath -> Aff String
read f = do
log ("File: " <> f) -- (1)
readTextFile UTF8 f -- (2)
I would like to do some debug logging in (1), before a potential error on (2) occurs. Executing following code in Spago REPL works for success cases so far:
$ spago repl
> launchAff_ $ read "test/data/tree/root.txt"
File: test/data/tree/root.txt
unit
Problem: If there is an error with (2) - file is directory here - , (1) seems to be not executed at all:
$ spago repl
> launchAff_ $ read "test/data/tree"
~/purescript-book/exercises/chapter9/.psci_modules/node_modules/Effect.Aff/foreign.js:532
throw util.fromLeft(step);
^
[Error: EISDIR: illegal operation on a directory, read] {
errno: -21,
code: 'EISDIR',
syscall: 'read'
}
The original problem is more complex including several layers of recursions (see E-Book exercise 3), where I need logging to debug above error.
Questions
How can I properly log regardless upcoming errors here?
(Optional) Is there a more sophisticated, well-established debugging alternative - purescript-debugger? A decicated VS Code debug extension/functionality would be the cherry on the cake.
First of all, the symptoms you observe do not mean that the first line doesn't execute. It does always execute, you're just not seeing output from it due to how console works in the PureScript REPL. The output gets swallowed. Not the only problem with REPL, sadly.
You can verify that the first line is always executed by replacing log with throwError and observing that the error always gets thrown. Or, alternatively, you can make the first line modify a mutable cell instead of writing to the console, and then examine the cell's contents.
Finally, this only happens in REPL. If you put that launchAff_ call inside main and run the program, you will always get the console output.
Now to the actual question at hand: how to debug trace.
Logging to console is fine if you can afford it, but there is a more elegant way: Debug.trace.
This function has a hidden effect - i.e. its type says it's pure, but it really produces an effect when called. This little lie lets you use trace in a pure setting and thus debug pure code. No need for Effect! This is ok as long as used for debugging only, but don't put it in production code.
The way it works is that it takes two parameters: the first one gets printed to console and the second one is a function to be called after printing, and the result of the whole thing is whatever that function returns. For example:
calculateSomething :: Int -> Int -> Int
calculateSomething x y =
trace ("x = " <> show x) \_ ->
x + y
main :: Effect Unit
main =
log $ show $ calculateSomething 37 5
> npx spago run
'x = 37'
42
The first parameter can be anything at all, not just a string. This lets you easily print a lot of stuff:
calculateSomething :: Int -> Int -> Int
calculateSomething x y =
trace { x, y } \_ ->
x + y
> npx spago run
{ x: 37, y: 5 }
42
Or, applying this to your code:
read :: FilePath -> Aff String
read f = trace ("File: " <> f) \_ -> do
readTextFile UTF8 f
But here's a subtle detail: this tracing happens as soon as you call read, even if the resulting Aff will never be actually executed. If you need tracing to happen on effectful execution, you'll need to make the trace call part of the action, and be careful not to make it the very first action in the sequence:
read :: FilePath -> Aff String
read f = do
pure unit
trace ("File: " <> f) \_ -> pure unit
readTextFile UTF8 f
It is, of course, a bit inconvenient to do this every time you need to trace in an effectful context, so there is a special function that does it for you - it's called traceM:
read :: FilePath -> Aff String
read f = do
traceM ("File: " <> f)
readTextFile UTF8 f
If you look at its source code, you'll see that it does exactly what I did in the example above.
The sad part is that trace won't help you in REPL when an exception happens, because it's still printing to console, so it'll still get swallowed for the same reasons.
But even when it doesn't get swallowed, the output is a bit garbled, because trace actually outputs in color (to help you make it out among other output), and PureScript REPL has a complicated relationship with color:
> calculateSomething 37 5
←[32m'x = 37'←[39m
42
In addition to Fyodor Soikin's great answer, I found a variant using VS Code debug view.
1.) Make sure to build with sourcemaps:
spago build --purs-args "-g sourcemaps"
2.) Add debug configuration to VS Code launch.json:
{
"version": "0.2.0",
"configurations": [
{
"type": "pwa-node",
"request": "launch",
"name": "Launch Program",
"skipFiles": ["<node_internals>/**"],
"runtimeArgs": ["-e", "require('./output/Main/index.js').main()"],
"smartStep": true // skips files without (valid) source map
}
]
}
Replace "./output/Main/index.js" / .main() with the compiled .js file / function to be debugged.
3.) Set break points and step through the .purs file via sourcemap support.
The following code gives the error
Expected 'while' in 'do-while' loop
if let path = NSBundle.mainBundle().pathForResource("Chapters", ofType: "txt"){
do {
let stringFromFile = try String(contentsOfFile:path, encoding: NSUTF8StringEncoding)
var chapters: [String] = stringFromFile.componentsSeparatedByString("#")
chapters.removeAtIndex(0)
} catch {
print((error))
}
}
it was working fine before, but now it's giving me an error. Does anyone know why?
That code works for me as-is in the Playground with the appropriate Chapters.txt file in the Resources folder; XCode 7.1 Build 7B60. Did you try Shift-Command-K for a Clean Build?
Something does not seem right with your error message. With Swift 2.0, there are no more do-while loops. They have been replaced by repeat-while loops instead. As your code snippet shows, do has been repurposed for do-try-catch error handling.
I was using RAMAnimatedTabBarController Module from here:
https://github.com/Ramotion/animated-tab-bar
I developed my entire application in swift 1.2 using Xcode 6 and the app was running perfectly . I wanted to try out "side loading" of my app using Xcode 7 which has swift 2.0. I had too many errors and I managed to solve most of the errors but three.
1) This line of code which is from that RAMAnimatedTabBarController module is throwing an error saying the function can't be evoked, when this perfectly compiled in Xcode 6:
var constranints = NSLayoutConstraint.constraintsWithVisualFormat(formatString,options:NSLayoutFormatOptions.DirectionRightToLeft,metrics: nil,views: containersDict as [NSObject : AnyObject])
the compiler error for this was:
Cannot invoke 'constraintsWithVisualFormat' with an argument list of
type '(String, options: NSLayoutFormatOptions, metrics: nil, views:
[NSObject : AnyObject])'
2) Another unusual error was thrown:
linker command failed with exit code 1 (use -v to see invocation)
3) And another:
(null): error: cannot parse the debug map for
"/Users/Rakshith/Library/Developer/Xcode/DerivedData/Blubot-heabwwmhqxxvctaabxkwcpgzsadx/Build/Intermediates/SwiftMigration/Blubot/Products/Debug-iphonesimulator/BlubotTests.xctest/BlubotTests":
No such file or directory
What is actually wrong with my project? It is still set to iOS 8.3.
Disable BitCode
Build Settings -> BitCode
I managed to correct the 2nd and 3rd error which most of you probably will face when you're running Xcode 7 Beta as well as Xcode 6.
Just solve these two errors by following the steps mentioned in this tread:
Xcode Version 6.1 (6A1030) - Apple Match O-Linker Error - Building
Try this method:
func createViewContainers() -> [String: UIView] {
var containersDict = [String: UIView]()
guard let tabBarItems = tabBar.items else
{
return containersDict
}
let itemsCount: Int = tabBarItems.count - 1
for index in 0...itemsCount {
let viewContainer = createViewContainer()
containersDict["container\(index)"] = viewContainer
}
var formatString = "H:|-(0)-[container0]"
for index in 1...itemsCount {
formatString += "-(0)-[container\(index)(==container0)]"
}
formatString += "-(0)-|"
let constranints = NSLayoutConstraint.constraintsWithVisualFormat(formatString,
options:NSLayoutFormatOptions.DirectionRightToLeft,
metrics: nil,
views: containersDict)
view.addConstraints(constranints)
return containersDict
}
how about to change the small code from "containersDict as [NSObject : AnyObject]" to "containersDict as [String : AnyObject]".
then I solved the issue above method.
Current behavior:
Put a breakpoint on the case Twice(n) ... line.
On "step into" the control goes to x match { line
On "step into" the control goes to def TwiceTest = { line
On further "step into" the control goes to if (z % 2 == 0)... line.
Expected behavior:
Put a breakpoint on the case Twice(n) ... line.
On "step into" the control goes to if (z % 2 == 0)... line.
Code Snippet
object testobj extends App {
def TwiceTest = {
val x = Twice(21)
x match {
case Twice(n) => Console.println(n)
} // prints 21
}
TwiceTest
}
object Twice {
def apply(x: Int): Int = x * 2
def unapply(z: Int): Option[Int] = {
if (z % 2 == 0) Some(z / 2) else None
}
}
The current behavior is irritating while debugging a scala program with lots of nested extractors. I tried this with the new Scala debugger as well as the Java debugger but with the same result.
Step Filtering also does not help in this case.
As a workaround, I am putting a breakpoint in the unapply method and running resume from the first breakpoint. Can someone please suggest me a cleaner method.
Edit 1
I am using Scala-IDE (latest nightly build. 2.1.0.nightly-2_09-201208250315-529cd70 )
Eclipse Version: Indigo Service Release 2 Build id: 20120216-1857
OS: Windows 7 ( 64 bit)
The line number information in the bytecode is wrong. It is not an issue with the IDE, but the Scala compiler. When pattern matching is compiled, synthetic code sometimes gets the wrong position information.
I assume you are using Scala 2.9.2. In the next version of Scala (2.10.0), there are significant improvements in the pattern matcher, so it would be good to give it a try.