cmd/compile: -gcflags="-m=2 -d=ssa/check_bce/debug=1" sometimes results in no output

[RaduBerinde]

Go version

go version go1.24.3 darwin/arm64

Output of go env in your module/workspace:

AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE='on'
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/radu/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/radu/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/x0/5yrxw_4s271g705vjscld23c0000gq/T/go-build680255877=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/radu/go/src/github.com/cockroachdb/pebble/go.mod'
GOMODCACHE='/Users/radu/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/radu/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/radu/go/pkg/mod/golang.org/[email protected]'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/radu/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/radu/go/pkg/mod/golang.org/[email protected]/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.3'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

In the Pebble (github.com/cockroachdb/pebble) master branch:

go build -gcflags="-m=2 -d=ssa/check_bce/debug=1" ./sstable/colblk

Note that we use this output (through github.com/jordanlewis/gcassert) for a linter that verifies that certain known hot paths are inlined.

What did you see happen?

The command outputs nothing.

What did you expect to see?

In go1.24.2 or older, I get a ton of information: https://gist.github.com/RaduBerinde/87145c7327fdf035de9a0008f4d841c5

[RaduBerinde]

Ah, interestingly go build -gcflags="-m=2" ./sstable/colblk seems to work. Maybe that -d flag is no longer valid? Seems like there should be some error output though.

[RaduBerinde]

This is very strange.. but after running the variant above, the original variant started working..

[gabyhelp]

Related Issues

• go tool compile #55111 (closed)
• cmd/go/internal/work/security.go: invalid flag in `#cgo LDFLAGS: -Wl,-rpath,.` #70924 (closed)
• go build #52634 (closed)
• cmd/go : "-gcflags -S" doesn't work when binary is present #26884 (closed)
• cmd/go/internal/work/security.go: invalid flag in `#cgo darwin LDFLAGS: -Wl,-rpath -Wl,@loader_path` #70923 (closed)
• cmd/go: go env -changed prints changed values for variables in go.env #67542 (closed)
• Test #67906 (closed)
• cmd/go: 1.8beta2 cross compilation fails without CGO_ENABLED=0 #18360 (closed)
• run #70024 (closed)
• sb #53220 (closed)

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

[mknyszek]

CC @golang/compiler

[mknyszek]

In triage we think this might be a caching issue. Something is getting cached and the output isn't getting cached and reprinted... or something.

[RaduBerinde]

It would make sense. If I can find a reliable way to reproduce, I'll update this issue.

[cherrymui]

Could you try if go clean -cache makes any difference? Thanks.

[RaduBerinde]

I tried that but after it started working fine already... I couldn't get it to fail anymore, with or without cleaning the cache.

[randall77]

The last paragraph of https://go-review.googlesource.com/c/go/+/128903, which fixed a bug like this a while ago, says:

This CL brings back the compiler and linker output in those two cases,
provided it can be found in the build cache. If it can't be found in the
build cache, then the go command still reuses the binaries and avoids
the compile/link/test steps. (It's not worth doing all that work again
just to repeat diagnostic output.)

I can use this to reproduce the behavior you're seeing. I'm not sure if this was the cause of what you saw, but maybe?

> cd <someproject>
> go build -gcflags="-m=2 -d=ssa/check_bce/debug=1"
... lots of debug output ...
> go clean -cache
> go build -gcflags="-m=2 -d=ssa/check_bce/debug=1"
... no debug output ...

In particular, you have to clean the cache but don't delete the binary produced in step 2.

Note that this happens just as well with -m=2 only.