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  1. c139306 Fix >50% in by Marc-Antoine Ruel · 5 days ago master v1.0.0
  2. fea9fd0 Switch vendoring to by Marc-Antoine Ruel · 5 days ago
  3. 868abbf Update .travis.yml and improve test output; drop 1.4, 1.6, 1.7 by Marc-Antoine Ruel · 4 weeks ago
  4. 2fd7e6e Update .travis.yml to explicitly test multiple Go versions by Marc-Antoine Ruel · 4 weeks ago
  5. bb2e7e2 source: fix brittle unit test by Marc-Antoine Ruel · 4 weeks ago


Parses panic stack traces, densifies and deduplicates goroutines with similar stack traces. Helps debugging crashes and deadlocks in heavily parallelized process.

Build Status

panicparse helps make sense of Go crash dumps:



  • >50% more compact output than original stack dump yet more readable.
  • Exported symbols are bold, private symbols are darker.
  • Stdlib is green, main is yellow, rest is red.
  • Deduplicates redundant goroutine stacks. Useful for large server crashes.
  • Arguments as pointer IDs instead of raw pointer values.
  • Pushes stdlib-only stacks at the bottom to help focus on important code.
  • Usable as a library! GoDoc
    • Warning: please pin the version (e.g. vendor it). Breaking changes are not planned but may happen.
  • Parses the source files if available to augment the output.
  • Works on Windows.


go get


Piping a stack trace from another process


  • Ubuntu (bash v4 or zsh): |&
  • OSX, install bash 4+, then: |&
  • Windows or OSX with stock bash v3: 2>&1 |
  • Fish shell: ^|

Longer version

pp streams its stdin to stdout as long as it doesn‘t detect any panic. panic() and Go’s native deadlock detector print to stderr via the native print() function.

Bash v4 or zsh: |& tells the shell to redirect stderr to stdout, it's an alias for 2>&1 | (bash v4, zsh):

go test -v |&pp

Windows or OSX native bash (which is 3.2.57): They don't have this shortcut, so use the long form:

go test -v 2>&1 | pp

Fish: It uses ^ for stderr redirection so the shortcut is ^|:

go test -v ^|pp

PowerShell: It has broken 2>&1 redirection. The workaround is to shell out to cmd.exe. :(

Investigate deadlock

On POSIX, use Ctrl-\ to send SIGQUIT to your process, pp will ignore the signal and will parse the stack trace.

Parsing from a file

To dump to a file then parse, pass the file path of a stack trace

go test 2> stack.txt
pp stack.txt



Starting with Go 1.6, GOTRACEBACK defaults to single instead of all / 1 that was used in 1.5 and before. To get all goroutines trace and not just the crashing one, set the environment variable:

export GOTRACEBACK=all

or set GOTRACEBACK=all on Windows. Probably worth to put it in your .bashrc.

Updating bash on OSX

Install bash v4+ on OSX via homebrew or macports. Your future self will appreciate having done that.

If you have /usr/bin/pp installed

If you try pp for the first time and you get:

Creating tables and indexes...


/usr/bin/pp5.18: No input files specified

you may be running the Perl PAR Packager instead of panicparse.

You have two choices, either you put $GOPATH/bin at the begining of $PATH or use long name panicparse with:

go get

then using panicparse instead of pp:

go test 2> panicparse