cmd/cgo: building c-archive with function pointer works with Go 1.14, but not 1.15 and beyond · golang/go#44648

2021-02-26T20:46:49.000Z

### What version of Go are you using (`go version`)? $ go version go version go1.15 darwin/amd64 ### Does this issue reproduce with the latest release? Yes. ### What operating system and processor architecture are you using (`go env`)? go env Output $ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/Users/willie/Library/Caches/go-build" GOENV="/Users/willie/Library/Application Support/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/willie/pkg/mod" GONOPROXY="github.com/vitalsource/*" GONOSUMDB="github.com/vitalsource/*" GOOS="darwin" GOPATH="/Users/willie" GOPRIVATE="github.com/vitalsource/*" GOPROXY="https://proxy.golang.org,direct" GOROOT="/Users/willie/.asdf/installs/golang/1.15/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/Users/willie/.asdf/installs/golang/1.15/go/pkg/tool/darwin_amd64" GCCGO="gccgo" AR="ar" CC="clang" CXX="clang++" CGO_ENABLED="1" GOMOD="/Users/willie/willie/cgotest/go.mod" 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/4z/2t7q40b14znb__08yd_p_znw0000gn/T/go-build009670235=/tmp/go-build -gno-record-gcc-switches -fno-common" ### What did you do? I build a Go c-archive static library to use in several C/C++ programs. Building c-archives with cgo broke in a way that I don't understand in Go 1.15 and later. Building with Go 1.14 works fine. I put together a simple example here: https://github.com/willie/cgotest ### What did you expect to see? I expected to be able to build a c-archive static library with no errors. ### What did you see instead? # command-line-arguments _cgo_export.c:29:3: error: unknown type name 'writeFunc'

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Description

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

Does this issue reproduce with the latest release?

Yes.

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

What did you do?

I build a Go c-archive static library to use in several C/C++ programs. Building c-archives with cgo broke in a way that I don't understand in Go 1.15 and later. Building with Go 1.14 works fine. I put together a simple example here: https://github.com/willie/cgotest

What did you expect to see?

I expected to be able to build a c-archive static library with no errors.

What did you see instead?

Contributor guide

Research direction: Investigate the cgo export mechanism in Go 1.15 that changed the handling of function pointer types when building c archive. Compare with Go 1.14 code to identify the cause of the 'unknown type name' error.
Tech stack: go
Domain: build system
Issue type: Bug
Difficulty: 3
Estimated time: 1-2 days
Activity status: Active
Clarity: Clear
Prerequisites: Go
Newbie friendliness: 60