[swift-users] stack trace of Swift executable

[Nick Snyder]

In practice, I would need the stack trace first to figure out how to
reproduce the issue, so lldb doesn't really help.

How would I go about symbolicating this further on macOS (Xcode or
otherwise)?

>From reading the docs it seems like the crash report I get is already
completely symbolicated:
https://developer.apple.com/library/content/technotes/tn2151/_index.html#//apple_ref/doc/uid/DTS40008184-CH1-SYMBOLICATION-_DETERMINING_WHETHER_A_CRASH_REPORT_IS_SYMBOLICATED

On Tue, May 2, 2017 at 1:21 AM, Alex Blewitt <alblue at apple.com> wrote:

> If you can reproduce it, and run it under lldb, it will print the source
> line for you:
>
> $ lldb .build/debug/main
> (lldb) target create ".build/debug/main"
> ruCurrent executable set to '.build/debug/main' (x86_64).
> (lldb) run
> Process 19013 launched: '/private/tmp/main/.build/debug/main' (x86_64)
> Hello, world!
> fatal error: unexpectedly found nil while unwrapping an Optional value
> 2017-05-02 09:17:11.351608+0100 asdf[19013:54205130] fatal error:
> unexpectedly found nil while unwrapping an Optional value
> Current stack trace:
> 0    libswiftCore.dylib                 0x00000001002c1160
> swift_reportError + 125
> 1    libswiftCore.dylib                 0x00000001002ddac0
> _swift_stdlib_reportFatalError + 60
> 2    libswiftCore.dylib                 0x00000001000ce260 specialized
> specialized StaticString.withUTF8Buffer<A> ((UnsafeBufferPointer<UInt8>) ->
> A) -> A + 342
> 3    libswiftCore.dylib                 0x0000000100249120 partial apply
> for (_fatalErrorMessage(StaticString, StaticString, file : StaticString,
> line : UInt, flags : UInt32) -> Never).(closure #2) + 109
> 4    libswiftCore.dylib                 0x00000001000ce260 specialized
> specialized StaticString.withUTF8Buffer<A> ((UnsafeBufferPointer<UInt8>) ->
> A) -> A + 342
> 5    libswiftCore.dylib                 0x00000001001fbd00 specialized
> _fatalErrorMessage(StaticString, StaticString, file : StaticString, line
> : UInt, flags : UInt32) -> Never + 96
> 6    main                               0x0000000100001340 say(message :
> String?) -> () + 248
> 7    main                               0x00000001000011e0 main + 328
> 8    libdyld.dylib                      0x00007fffb444d234 start + 1
> Process 19013 stopped
> * thread #1, queue = 'com.apple.main-thread', stop reason =
> EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
>     frame #0: 0x00000001001fbd60 libswiftCore.dylib`function signature
> specialization <preserving fragile attribute, Arg[2] = Dead, Arg[3] = Dead>
> of Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, file :
> Swift.StaticString, line : Swift.UInt, flags : Swift.UInt32) -> Swift.Never
> + 96
> libswiftCore.dylib`function signature specialization <preserving fragile
> attribute, Arg[2] = Dead, Arg[3] = Dead> of Swift._fatalErrorMessage
> (Swift.StaticString, Swift.StaticString, file : Swift.StaticString, line :
> Swift.UInt, flags : Swift.UInt32) -> Swift.Never:
> ->  0x1001fbd60 <+96>: ud2
>     0x1001fbd62 <+98>: nopw   %cs:(%rax,%rax)
>
> libswiftCore.dylib`protocol witness table accessor for <A>
> Swift.AnySequence<A> : Swift.Sequence in Swift:
>     0x1001fbd70 <+0>:  pushq  %rbp
>     0x1001fbd71 <+1>:  movq   %rsp, %rbp
>
> (lldb) bt
> * thread #1, queue = 'com.apple.main-thread', stop reason =
> EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)
>   * frame #0: 0x00000001001fbd60 libswiftCore.dylib`function signature
> specialization <preserving fragile attribute, Arg[2] = Dead, Arg[3] = Dead>
> of Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, file :
> Swift.StaticString, line : Swift.UInt, flags : Swift.UInt32) -> Swift.Never
> + 96
> *    frame #1: 0x0000000100001438 main`say(message=nil) -> () at
> main.swift:5*
> *    frame #2: 0x0000000100001328 main`main at main.swift:8*
>     frame #3: 0x00007fffb444d235 libdyld.dylib`start + 1
>     frame #4: 0x00007fffb444d235 libdyld.dylib`start + 1
>
> There is a symbolication tool available for Linux in the
> ~/swift/utils/symbolicate-linux-fatal, and Xcode can do the same
> symbolication for you as well.
>
> Alex
>
> On 28 Apr 2017, at 22:28, Nick Snyder via swift-users <
> swift-users at swift.org> wrote:
>
> I have a simple main.swift that looks like this:
>
> ```
> print("Hello, world!")
> let x: String? = nil
>
> func say(message: String?) {
>     print(x!) // intentional crash
> }
>
> say(message: x)
> ```
>
> Running this results in the crash
>
> ```
> $ swift build && ./.build/debug/hello
> Hello, world!
> fatal error: unexpectedly found nil while unwrapping an Optional value
> Current stack trace:
> 0    libswiftCore.dylib                 0x0000000110120130
> swift_reportError + 129
> 1    libswiftCore.dylib                 0x000000011013cb50
> _swift_stdlib_reportFatalError + 60
> 2    libswiftCore.dylib                 0x000000010ff2d250 specialized
> specialized StaticString.withUTF8Buffer<A> ((UnsafeBufferPointer<UInt8>) ->
> A) -> A + 342
> 3    libswiftCore.dylib                 0x00000001100a7e90 partial apply
> for (_fatalErrorMessage(StaticString, StaticString, file : StaticString,
> line : UInt, flags : UInt32) -> Never).(closure #2) + 109
> 4    libswiftCore.dylib                 0x000000010ff2d250 specialized
> specialized StaticString.withUTF8Buffer<A> ((UnsafeBufferPointer<UInt8>) ->
> A) -> A + 342
> 5    libswiftCore.dylib                 0x000000011005a9a0 specialized
> _fatalErrorMessage(StaticString, StaticString, file : StaticString, line
> : UInt, flags : UInt32) -> Never + 96
> 6    hello                              0x000000010fee6200 main + 345
> 7    libdyld.dylib                      0x00007fffe0375234 start + 1
> Illegal instruction: 4
> ```
>
> From the crash, how do I map back line 6 to an actual line in main.swift?
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