runtime.Callers does not include all callers.

[uberbo]

What version of Go are you using (go version)?

go version go1.12beta1 darwin/amd64

Does this issue reproduce with the latest release?

It is not on the latest non-beta release.

What operating system and processor architecture are you using (go env)?

go env Output

GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/bos/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/bos/gocode"
GOPROXY=""
GORACE=""
GOROOT="/Users/bos/sdk/go1.12beta1"
GOTMPDIR=""
GOTOOLDIR="/Users/bos/sdk/go1.12beta1/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/zx/8zmf02c16knfz261k7w0p12m0000gn/T/go-build733608340=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

https://play.golang.org/p/dduJxdG9L1U

What did you expect to see?

0: runtime.Callers
1: main.getFunctionNames
2: main.functionCallingGetFunctionNames
3: main.main
4: runtime.main
5: runtime.goexit

What did you see instead?

0: runtime.Callers
1: main.getFunctionNames
2: main.main
3: runtime.main
4: runtime.goexit

[Neverik]

Maybe it's just improved inlining (i.e. because functionCallingGetFunctionNames was short, its body got inserted into the call site)?

See https://github.com/golang/go/wiki/CompilerOptimizations#function-inlining for more info.

You can check whether it was actually inlined using -gcflags -m when compiling with go build.

[uberbo]

Maybe it's just improved inlining (i.e. because functionCallingGetFunctionNames was short, its body got inserted into the call site)?

See https://github.com/golang/go/wiki/CompilerOptimizations#function-inlining for more info.

You can check whether it was actually inlined using -gcflags -m when compiling with go build.

That sounds very likely, it will make stack traces from https://github.com/pkg/errors look weird though. E.g:

main.getFunctionNames
	/gocode/src/github.com/pkg/errors/errors.go:104
runtime.skipPleaseUseCallersFrames
	/sdk/go1.12beta1/src/runtime/asm.s:40
main.main
	/gocode/src/playground/go12beta/main.go:22
runtime.main
	/sdk/go1.12beta1/src/runtime/proc.go:200
runtime.goexit
	/sdk/go1.12beta1/src/runtime/asm_amd64.s:1337

Whereas go 1.11.4 produces:

main.getFunctionNames
	/gocode/src/playground/go12beta/main.go:44
main.functionCallingGetFunctionNames
	/gocode/src/playground/go12beta/main.go:31
main.main
	/gocode/src/playground/go12beta/main.go:15
runtime.main
	/usr/local/Cellar/go/1.11.4/libexec/src/runtime/proc.go:201
runtime.goexit
	/usr/local/Cellar/go/1.11.4/libexec/src/runtime/asm_amd64.s:1333

[uberbo]

Even if I add logic to the dummy function that prevents inlining, the stack tracing looks incorrect.
https://play.golang.org/p/EdwAz1v3a1Y

main.getFunctionNames
	/gocode/src/github.com/pkg/errors/errors.go:104
runtime.skipPleaseUseCallersFrames
	/sdk/go1.12beta1/src/runtime/asm.s:40
main.functionCallingGetFunctionNames
	/gocode/src/playground/go12beta/main.go:32
main.main
	/gocode/src/playground/go12beta/main.go:16
runtime.main
	/sdk/go1.12beta1/src/runtime/proc.go:200
runtime.goexit
	/sdk/go1.12beta1/src/runtime/asm_amd64.s:1337

It still contains skipPleaseUseCallersFrames and it uses the wrong file for main.getFunctionNames.

[cherrymui]

It still contains skipPleaseUseCallersFrames

As this name suggests, as well as documented in https://golang.org/pkg/runtime/#Callers, please use runtime.CallersFrames (https://golang.org/pkg/runtime/#CallersFrames) instead of FuncForPC over the PCs.