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Dump collection and analysis utility (dotnet-dump)

The dotnet-dump CLI global tool is way to collect and analyze Windows and Linux dumps all without any native debugger involved like lldb on Linux. This is important on platforms like Alpine Linux or Linux ARM32/ARM64 where a fully working lldb isn't available. The dotnet-dump tool will allow you to run SOS commands to analyze crashes and the GC, but it isn't a native debugger so things like displaying the native stack frames isn't supported.

Currently not supported on macOS.

Installing dotnet-dump

The first step is to install the dotnet-dump CLI global tool. This requires at least the 2.1 or greater .NET Core SDK to be installed. If you see the error message Tool 'dotnet-dump' is already installed, you will need to uninstall the global tool (see below).

$ dotnet tool install -g dotnet-dump --version 3.0.0-preview9.19454.1
You can invoke the tool using the following command: dotnet-dump
Tool 'dotnet-dump' (version '3.0.0-preview9.19454.1') was successfully installed.

If this is the first global tool installed or you get message Could not execute because the specified command or file was not found. you need to add $HOME/.dotnet/tools to your path.

export PATH=$PATH:$HOME/.dotnet/tools

Using dotnet-dump

The next step is to collect a dump. This can be skipped if a core dump has already been generated by the operating system or createdump on Linux.

On Linux, the runtime version must be 3.0 or greater. On Windows, dotnet-dump collect will work with any version of the runtime.

$ dotnet-dump collect --process-id 1902
Writing minidump to file ./core_20190226_135837
Written 98983936 bytes (24166 pages) to core file
Complete

If you are running under docker, dump collection requires SYS_PTRACE docker capabilities (--cap-add=SYS_PTRACE or --privileged).

Now analyze the core dump.

$ dotnet-dump analyze ./core_20190226_135850
Loading core dump: ./core_20190226_135850
Ready to process analysis commands. Type 'help' to list available commands or 'help [command]' to get detailed help on a command.
Type 'quit' or 'exit' to exit the session.
>

This brings up an interactive command processor that accepts commands like:

> clrstack
OS Thread Id: 0x573d (0)
    Child SP               IP Call Site
00007FFD28B42C58 00007fb22c1a8ed9 [HelperMethodFrame_PROTECTOBJ: 00007ffd28b42c58] System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Object[], System.Signature, Boolean, Boolean)
00007FFD28B42DD0 00007FB1B1334F67 System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo) [/root/coreclr/src/mscorlib/src/System/Reflection/RuntimeMethodInfo.cs @ 472]
00007FFD28B42E20 00007FB1B18D33ED SymbolTestApp.Program.Foo4(System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 54]
00007FFD28B42ED0 00007FB1B18D2FC4 SymbolTestApp.Program.Foo2(Int32, System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 29]
00007FFD28B42F00 00007FB1B18D2F5A SymbolTestApp.Program.Foo1(Int32, System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 24]
00007FFD28B42F30 00007FB1B18D168E SymbolTestApp.Program.Main(System.String[]) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 19]
00007FFD28B43210 00007fb22aa9cedf [GCFrame: 00007ffd28b43210]
00007FFD28B43610 00007fb22aa9cedf [GCFrame: 00007ffd28b43610]

To see the unhandled exception if your app was terminated:

> pe -lines
Exception object: 00007fb18c038590
Exception type:   System.Reflection.TargetInvocationException
Message:          Exception has been thrown by the target of an invocation.
InnerException:   System.Exception, Use !PrintException 00007FB18C038368 to see more.
StackTrace (generated):
SP               IP               Function
00007FFD28B42DD0 0000000000000000 System.Private.CoreLib.dll!System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Object[], System.Signature, Boolean, Boolean)
00007FFD28B42DD0 00007FB1B1334F67 System.Private.CoreLib.dll!System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)+0xa7 [/root/coreclr/src/mscorlib/src/System/Reflection/RuntimeMethodInfo.cs @ 472]
00007FFD28B42E20 00007FB1B18D33ED SymbolTestApp.dll!SymbolTestApp.Program.Foo4(System.String)+0x15d [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 54]
00007FFD28B42ED0 00007FB1B18D2FC4 SymbolTestApp.dll!SymbolTestApp.Program.Foo2(Int32, System.String)+0x34 [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 29]
00007FFD28B42F00 00007FB1B18D2F5A SymbolTestApp.dll!SymbolTestApp.Program.Foo1(Int32, System.String)+0x3a [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 24]
00007FFD28B42F30 00007FB1B18D168E SymbolTestApp.dll!SymbolTestApp.Program.Main(System.String[])+0x6e [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 19]

StackTraceString: HResult: 80131604

To display the help:

> help
Usage:
  dotnet-dump [command]

Commands:
  exit, quit                           Exit interactive mode.
  help, soshelp <command>              Display help for a command.
  lm, modules                          Displays the native modules in the process.
  threads, setthread <threadid>        Sets or displays the current thread id for the SOS commands.
  clrstack <arguments>                 Provides a stack trace of managed code only.
  clrthreads <arguments>               List the managed threads running.
  dumpasync <arguments>                Displays info about async state machines on the garbage-collected heap.
  dumpassembly <arguments>             Displays details about an assembly.
  dumpclass <arguments>                Displays information about a EE class structure at the specified address.
  dumpdelegate <arguments>             Displays information about a delegate.
  dumpdomain <arguments>               Displays information all the AppDomains and all assemblies within the domains.
  dumpheap <arguments>                 Displays info about the garbage-collected heap and collection statistics about objects.
  dumpil <arguments>                   Displays the Microsoft intermediate language (MSIL) that is associated with a managed method.
  dumplog <arguments>                  Writes the contents of an in-memory stress log to the specified file.
  dumpmd <arguments>                   Displays information about a MethodDesc structure at the specified address.
  dumpmodule <arguments>               Displays information about a EE module structure at the specified address.
  dumpmt <arguments>                   Displays information about a method table at the specified address.
  dumpobj <arguments>                  Displays info about an object at the specified address.
  dso, dumpstackobjects <arguments>    Displays all managed objects found within the bounds of the current stack.
  eeheap <arguments>                   Displays info about process memory consumed by internal runtime data structures.
  finalizequeue <arguments>            Displays all objects registered for finalization.
  gcroot <arguments>                   Displays info about references (or roots) to an object at the specified address.
  gcwhere <arguments>                  Displays the location in the GC heap of the argument passed in.
  ip2md <arguments>                    Displays the MethodDesc structure at the specified address in code that has been JIT-compiled.
  name2ee <arguments>                  Displays the MethodTable structure and EEClass structure for the specified type or method in the specified module.
  pe, printexception <arguments>       Displays and formats fields of any object derived from the Exception class at the specified address.
  syncblk <arguments>                  Displays the SyncBlock holder info.
  histclear <arguments>                Releases any resources used by the family of Hist commands.
  histinit <arguments>                 Initializes the SOS structures from the stress log saved in the debuggee.
  histobj <arguments>                  Examines all stress log relocation records and displays the chain of garbage collection relocations that may have led to the address passed in as an argument.
  histobjfind <arguments>              Displays all the log entries that reference an object at the specified address.
  histroot <arguments>                 Displays information related to both promotions and relocations of the specified root.
  setsymbolserver <arguments>          Enables the symbol server support
  soshelp <arguments>                  Displays all available commands when no parameter is specified, or displays detailed help information about the specified command. soshelp <command>

This command on Microsoft .NET Core SDK Linux docker images can throw Unhandled exception: System.DllNotFoundException: Unable to load shared library 'libdl.so' or one of its dependencies exception. To work around this problem install the "libc6-dev" package.

Uninstalling dotnet-dump

$ dotnet tool uninstall -g dotnet-dump
Tool 'dotnet-dump' (version '3.0.0-preview9.19454.1') was successfully uninstalled.
You can’t perform that action at this time.