cmd/cgo: mishandles untyped constants in some cases #30527
Description
What version of Go are you using (go version)?
$ go version go version go1.12 linux/amd64
Does this issue reproduce with the latest release?
Yes, but it does not happen with go 1.11.5
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GOARCH="amd64" GOBIN="" GOCACHE="/home/remy/.cache/go-build" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOOS="linux" GOPATH="/home/remy/travail/go:/storage/remy/gopath" GOPROXY="" GORACE="" GOROOT="/usr/lib/go" GOTMPDIR="" GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64" GCCGO="gccgo" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="" 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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build301410002=/tmp/go-build -gno-record-gcc-switches"
What did you do?
Create a 2-file package which invokes a C function with untyped constants.
% cat a.go
package pkg
import "fmt"
import "math"
/*
#include
typedef struct {
uint64_t a;
uint64_t b;
void *next;
} T;
uint64_t mul(T *x, uint64_t mod, uint32_t unused) {
return (x->a * x->b);
}
*/
import "C"
func F() {
t := &C.T{a: 1, b: 2, next: nil}
n := C.mul(t, math.MaxUint64, 1)
fmt.Println(n)
}
func G() {
t := &C.T{a: 1, b: 2, next: nil}
n := C.mul(t, 1<<64-1, z)
fmt.Println(n)
}
% cat b.go
package pkg
const (
x = 1 << iota
y
z
)
What did you expect to see?
Successful compilation (as with go1.11.5)
What did you see instead?
./a.go:24:94: cannot use _cgo1 (type int) as type _Ctype_ulong in argument to _Cfunc_mul ./a.go:24:22: constant 18446744073709551615 overflows int ./a.go:31:70: cannot use _cgo2 (type int) as type _Ctype_uint in argument to _Cfunc_mul
The error disappears if MaxUint64 is defined in the same package, or if z is defined in the same file.