cmd/pprof: runtime panic index out of range if given empty cpu.prof

[gopherbot]

by jgardner@izeni.com:

go version go1.4rc2 linux/amd64

Here's the output: 

go tool pprof -svg ./chatads-keyword-extraction /tmp/profile223797702/cpu.pprof
panic: runtime error: index out of range
 
goroutine 1 [running]:
cmd/pprof/internal/driver.sampleFormat(0xc20808a000, 0xc208092000, 0xc2080c8240, 0x0,
0x0, 0x0, 0x0)
        /usr/src/go/src/cmd/pprof/internal/driver/driver.go:975 +0x21c
cmd/pprof/internal/driver.generate(0xc20808a000, 0xc20808a000, 0x7f0b01303ff0,
0xc20802afc0, 0x7f0b01303fa8, 0xc20804e060, 0xc208092000, 0x0, 0x0)
        /usr/src/go/src/cmd/pprof/internal/driver/driver.go:1012 +0x11f
cmd/pprof/internal/driver.PProf(0x7f0b01304030, 0xae7048, 0x96fb50, 0x970118,
0x7f0b01303ff0, 0xc20802afc0, 0x7f0b01303fa8, 0xc20804e060, 0x0, 0x0, ...)
        /usr/src/go/src/cmd/pprof/internal/driver/driver.go:115 +0xc8d
main.main()
        /usr/src/go/src/cmd/pprof/pprof.go:28 +0x129

Attachments:

1. chatads-keyword-extraction (8560645 bytes)
2. cpu.pprof (0 bytes)

[davecheney]

Comment 1:

The profile file is zero bytes. Is this intentional? Just checking to see if this wasn't
a mistake when uploading the file.

[minux]

Comment 2:

i think that explains the crash.

[gopherbot]

Comment 3 by jgardner@izeni.com:

It wasn't intentional for the profile file to be empty but it was and that explains the
crash I think too.

[minux]

Comment 4:

Not important enough for 1.4.

Labels changed: added release-none, repo-main.

Status changed to Accepted.

[se77en]

encounter same issue :(

[osocurioso]

I'd like to try my hand at this. Seems like a perfect issue for a first-timer.

[minux]

Sure, please go ahead.

The contribution guideline is here:
golang.org/doc/contribute.html

Please note that it's not as simple as adding a check for
len() > 0, you will need to find the right place to check
for empty profiles (or more generally, malformed profiles)

[osocurioso]

I actually ended up with a simple check for len() == 0, only carefully placed. See golang.org/cl/2571. There was already a fair bit of checking for malformed data there but this particular case was missed.

[osocurioso]

Clickable link: http://golang.org/cl/2571