runtime: crash message not included in debug.SetCrashOutput

[dsnet]

Go version

go1.25

Output of go env in your module/workspace:

n/a

What did you do?

Call debug.SetCrashOutput and run a program that deliberately causes a fatal error.

What did you see happen?

I see crash.txt only include a bunch of stack traces.

What did you expect to see?

I expect crash.txt to start with:

fatal error: concurrent map writes

Note that a regular panic that is not recovered includes the panic message in the crash output, so the intent seems to be that the fatal message should be captured.

[gopherbot]

Change https://go.dev/cl/730580 mentions this issue: runtime: include throw and fatal message in SetCrashOutput

[gabyhelp]

Related Issues

• runtime: printing multiple fatal errors may interleave messages #69447 (closed)
• runtime/debug: add SetCrashOutput(file *os.File) #42888 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[prattmic]

Plenty of throws also have additional context printed ad-hoc before the throw call. e.g., https://cs.opensource.google/go/go/+/master:src/runtime/traceback.go;l=467-471;drc=d2aad0df601df3a48ee4823309872cd224d91aa3

Longer term we may want to consider including such output as well.

[DasPoet]

This would be awesome to have. We have resorted to parsing stderr in addition to using debug.SetCrashOutput, which is not ideal.