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rittneje opened this issue Jan 10, 2025 · 3 comments
Closed

cmd/cgo: unused parameter when exporting Go function #71225

rittneje opened this issue Jan 10, 2025 · 3 comments
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BugReport Issues describing a possible bug in the Go implementation. compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Backlog

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@rittneje
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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 of the issue.

package main

/*
#cgo CFLAGS: -Werror -Wunused-parameter
*/
import "C"

func main() {

}

//export foo
func foo() {

}

What did you see happen?

$ go build
# command-line-arguments
cgo-generated-wrappers:1:37: error: unused parameter 'p' [-Werror,-Wunused-parameter]

I believe it is referring to _cgo_main.c, which looks like this:

#include <stddef.h>
int main() { return 0; }
void crosscall2(void(*fn)(void*) __attribute__((unused)), void *a __attribute__((unused)), int c __attribute__((unused)), size_t ctxt __attribute__((unused))) { }
size_t _cgo_wait_runtime_init_done(void) { return 0; }
void _cgo_release_context(size_t ctxt __attribute__((unused))) { }
char* _cgo_topofstack(void) { return (char*)0; }
void _cgo_allocate(void *a __attribute__((unused)), int c __attribute__((unused))) { }
void _cgo_panic(void *a __attribute__((unused)), int c __attribute__((unused))) { }
void _cgo_reginit(void) { }
#line 1 "cgo-generated-wrappers"
void _cgoexp_d15c4901095e_foo(void* p){}

What did you expect to see?

No errors.
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Jan 10, 2025
@gabyhelp
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Related Issues

Related Code Changes

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

@gabyhelp gabyhelp added the BugReport Issues describing a possible bug in the Go implementation. label Jan 10, 2025
@gabyhelp gabyhelp mentioned this issue Jan 10, 2025
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@prattmic
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cc @golang/compiler

@prattmic prattmic added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jan 10, 2025
@gopherbot
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Change https://go.dev/cl/642196 mentions this issue: cmd/cgo: add C declaration parameter unused attribute

@mknyszek mknyszek moved this to All-But-Submitted in Go Compiler / Runtime Jan 22, 2025
@mknyszek mknyszek added this to the Backlog milestone Jan 22, 2025
@github-project-automation github-project-automation bot moved this from All-But-Submitted to Done in Go Compiler / Runtime Feb 3, 2025
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Labels
BugReport Issues describing a possible bug in the Go implementation. compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Projects
Go Compiler / Runtime
Status: Done
Milestone
Backlog
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@mknyszek @prattmic @gopherbot @rittneje @gabyhelp