var (
	swigOnce sync.Once
	haveSwig bool
)

func mustHaveSwig(t *testing.T) {
	swigOnce.Do(func() {
		mustHaveSwigOnce(t)
		haveSwig = true
	})
	// The first call will skip t with a nice message. On later calls, we just skip.
	if !haveSwig {
		t.Skip("swig not found")
	}
}

func mustHaveSwigOnce(t *testing.T) {
	swig, err := exec.LookPath("swig")
	if err != nil {
		t.Skipf("swig not in PATH: %s", err)
	}

## Ports {#ports}

### Darwin {#darwin}

<!-- go.dev/issue/64207 -->
As [announced](go1.22#darwin) in the Go 1.22 release notes,
Go 1.23 requires macOS 11 Big Sur or later;
support for previous versions has been discontinued.

### Wasm {#wasm}

<!-- go.dev/issue/63718 -->
The `go_wasip1_wasm_exec` script in `GOROOT/misc/wasm` has dropped support

		}
	}
}

// Save various references we are going to need later.
func (f *File) saveExprs(x interface{}, context astContext) {
	switch x := x.(type) {
	case *ast.Expr:
		switch (*x).(type) {
		case *ast.SelectorExpr:
			f.saveRef(x, context)
		}
	case *ast.CallExpr:
		f.saveCall(x, context)
	}
}

// Save references to C.xxx for later processing.
func (f *File) saveRef(n *ast.Expr, context astContext) {

parsing these is significantly less work and more robust than parsing
C source.

Cgo first invokes gcc -E -dM on the preamble, in order to find out
about simple #defines for constants and the like. These are recorded
for later use.

Next, cgo needs to identify the kinds for each identifier. For the
identifiers C.foo, cgo generates this C program:

	<preamble>
	#line 1 "not-declared"

pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_LOOPBACK = 36864
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_LOOPBACK ideal-int
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_MATRA = 32890
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_MATRA ideal-int
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_MAX = 65535
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_MAX ideal-int
pkg syscall (netbsd-arm64-cgo), const ETHERTYPE_MERIT = 32892

The expression <code>x</code> is evaluated and saved during the evaluation of the
method value; the saved copy is then used as the receiver in any calls,
which may be executed later.
</p>

<pre>
type S struct { *T }
type T int
func (t T) M() { print(t) }

t := new(T)
s := S{T: t}
f := t.M                    // receiver *t is evaluated and stored in f

is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.
The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer)
can be used to revert back to asynchronous channel behaviors

The expression <code>x</code> is evaluated and saved during the evaluation of the
method value; the saved copy is then used as the receiver in any calls,
which may be executed later.
</p>

<pre>
type S struct { *T }
type T int
func (t T) M() { print(t) }

t := new(T)
s := S{T: t}
f := t.M                    // receiver *t is evaluated and stored in f

pkg syscall (netbsd-386), const ETHERTYPE_LITTLE = 32864
pkg syscall (netbsd-386), const ETHERTYPE_LOGICRAFT = 33096
pkg syscall (netbsd-386), const ETHERTYPE_LOOPBACK = 36864
pkg syscall (netbsd-386), const ETHERTYPE_MATRA = 32890
pkg syscall (netbsd-386), const ETHERTYPE_MAX = 65535
pkg syscall (netbsd-386), const ETHERTYPE_MERIT = 32892
pkg syscall (netbsd-386), const ETHERTYPE_MICP = 34618

pkg debug/elf, const EM_78KOR = 199
pkg debug/elf, const EM_78KOR Machine
pkg debug/elf, const EM_8051 = 165
pkg debug/elf, const EM_8051 Machine
pkg debug/elf, const EM_ALTERA_NIOS2 = 113
pkg debug/elf, const EM_ALTERA_NIOS2 Machine
pkg debug/elf, const EM_AMDGPU = 224
pkg debug/elf, const EM_AMDGPU Machine
pkg debug/elf, const EM_ARCA = 109
pkg debug/elf, const EM_ARCA Machine
pkg debug/elf, const EM_ARC_COMPACT = 93