defer func() {
		if err := b.Close(); err != nil {
			base.Fatal(err)
		}
	}()

	cppflags, cflags, cxxflags, fflags, ldflags, err := b.CFlags(&load.Package{})
	if err != nil {
		// Should not happen - b.CFlags was given an empty package.
		fmt.Fprintf(os.Stderr, "go: invalid cflags: %v\n", err)
		return nil
	}
	cmd := b.GccCmd(".", "")

	join := func(s []string) string {

   return c;
}

// issue 4857
#cgo CFLAGS: -Werror
const struct { int a; } *issue4857() { return (void *)0; }

// issue 5224
// Test that the #cgo CFLAGS directive works,
// with and without platform filters.
#cgo CFLAGS: -DCOMMON_VALUE=123
#cgo windows CFLAGS: -DIS_WINDOWS=1
#cgo !windows CFLAGS: -DIS_WINDOWS=0
int common = COMMON_VALUE;
int is_windows = IS_WINDOWS;

effect to systems satisfying one of the constraints
(see https://golang.org/pkg/go/build/#hdr-Build_Constraints for details about the constraint syntax).
For example:

	// #cgo CFLAGS: -DPNG_DEBUG=1
	// #cgo amd64 386 CFLAGS: -DX86=1
	// #cgo LDFLAGS: -lpng
	// #include <png.h>
	import "C"

Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config tool

		C code.
	CGO_CFLAGS_ALLOW
		A regular expression specifying additional flags to allow
		to appear in #cgo CFLAGS source code directives.
		Does not apply to the CGO_CFLAGS environment variable.
	CGO_CFLAGS_DISALLOW
		A regular expression specifying flags that must be disallowed
		from appearing in #cgo CFLAGS source code directives.
		Does not apply to the CGO_CFLAGS environment variable.

TEXT ·x(SB),0,$0
        CALL foo(SB)
        RET
`)
	write("x.c", `
void undefined();

void foo() {
        undefined();
}
`)

	cc := strings.TrimSpace(runGo("env", "CC"))
	cflags := strings.Fields(runGo("env", "GOGCCFLAGS"))

	importcfgfile := filepath.Join(tmpdir, "importcfg")
	testenv.WriteImportcfg(t, importcfgfile, nil, "runtime")

	// Compile, assemble and pack the Go and C code.