cmd/link: unexpected R_386_GOT32 relocation

[dbenoit17]

Go version

go version go1.23.4 linux/386

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='386'
GOBIN=''
GOCACHE='/builddir/.cache/go-build'
GOENV='/builddir/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='386'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/builddir/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/builddir/go'
GOPRIVATE=''
GOPROXY='direct'
GOROOT='/usr/lib/golang'
GOSUMDB='off'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/usr/lib/golang/pkg/tool/linux_386'
GOVCS=''
GOVERSION='go1.23.4'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/builddir/.config/go/telemetry'
GCCGO='gccgo'
GO386='sse2'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m32 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3544270386=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Compile the following program using GCC 15.0.1.

sh-5.2# gcc --version
gcc (GCC) 15.0.1 20250114 (Red Hat 15.0.1-0)

sh-5.2# cat test.go
package main

/*
extern void crosscall2 (void (*fn) (void *, int), void *, int);
extern void _cgo_panic (void *, int);
extern void _cgo_allocate (void *, int);

void
callPanic (void)
{
	  struct { const char *p; } a;
	  a.p = "panic from C";
	  crosscall2 (_cgo_panic, &a, sizeof a);
	  *(int*) 1 = 1;
}
*/
import "C"

func main() {
	C.callPanic()
}

sh-5.2# CGO_CFLAGS="-O2 -m32 -fpic" go build -ldflags "-linkmode internal" test.go 

This issue is also present when running go tool dist test -run=^cmd/cgo/internal/test:internal$ using GCC 15.0.1.

What did you see happen?

The Go linker encounters an unexpected relocation in GCC emitted object code.

sh-5.2# CGO_CFLAGS="-O2 -m32 -fpic" go build -ldflags "-linkmode internal" test.go 
# command-line-arguments
main(.text): unexpected GOT reloc for non-dynamic symbol _cgo_panic
main(.text): unsupported dynamic relocation for symbol _cgo_panic (type=259 (R_386_GOT32) stype=1 (STEXT))

The linker is expecting to find the instruction pushl _cgo_panic@GOT(%ebx), but instead encounters pushl _cgo_panic@GOT(%eax). According to gcc devs, this is valid (though sub optimal) code that the Go linker should handle.

What did you expect to see?

The example program should build and link correctly.

[mknyszek]

CC @golang/compiler