cmd/cgo: _GoStringLen and _GoStringPtr implicitly declared when exporting Go function

[rittneje]

Go version

go version go1.22.10 darwin/amd64

Output of go env in your module/workspace:

GO111MODULE='auto'
GOARCH='amd64'
GOBIN=''
GOCACHE='/tmp/.gocache'
GOENV='/Users/rittneje/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/rittneje/test/pkg/mod'
GONOPROXY='[redacted]'
GONOSUMDB='[redacted]'
GOOS='darwin'
GOPATH='/Users/rittneje/test'
GOPRIVATE='[redacted]'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/rittneje/go1.22.10'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/Users/rittneje/go1.22.10/pkg/tool/darwin_amd64'
GOVCS='[redacted]'
GOVERSION='go1.22.10'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/rittneje/test/src/cgotest/go.mod'
GOWORK='/Users/rittneje/test/go.work'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/kf/kr7_s3xx0l12zbj3jrn082hmzy5gvy/T/go-build3787749113=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

I am writing an application that uses cgo. For this reason, I want to compile with all warnings as errors.

Here is a minimal reproducer:

package main

/*
#cgo CFLAGS: -Werror -Wimplicit-function-declaration

void bar(_GoString_ str) {
	_GoStringLen(str);
	_GoStringPtr(str);
}
*/
import "C"

func main() {
}

//export foo
func foo() {
}

What did you see happen?

$ go build
# cgotest
In file included from _cgo_export.c:4:
main.go:7:2: error: call to undeclared function '_GoStringLen'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
main.go:8:2: error: call to undeclared function '_GoStringPtr'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

Without the //export foo directive, it compiles without issue.

What did you expect to see?

No errors.

[gabyhelp]

Related Issues

• cmd/cgo: _GoStringLen/_GoStringPtr not available with exported functions in c-archive or c-shared modes #48824 (closed)
• cmd/cgo: main declared without a prototype #70769 (closed)
• cmd/cgo: unused parameter when exporting Go function #71225
• cmd/cgo: _GoString_ is unavailable #24097 (closed)
• cmd/cgo: definition of GoString is incorrect for exported functions #5548 (closed)
• cmd/cgo: c code that was compiled with go, cannot also be used by go #27019 (closed)
• cmd/go: reports errors for a correct preamble when it contains a builtin C type and a `C.*` name can't be resolved #50710 (closed)
• go/build: imports from cgo files included in Imports when CGO_ENABLED=0 #35946 (closed)
• cmd/go: give a better error message when building Go package with CGO_ENABLED=0 #24068
• cmd/link:cgo: reports multiple definitions of C land function #63408 (closed)

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

[prattmic]

cc @golang/compiler

[gopherbot]

Change https://go.dev/cl/642235 mentions this issue: cmd/cgo: declare _GoString{Len,Ptr} in _cgo_export.h