q, err := quoted.Join(s)
		if err != nil {
			return strings.Join(s, " ")
		}
		return q
	}

	ret := []cfg.EnvVar{
		// Note: Update the switch in runEnv below when adding to this list.
		{Name: "CGO_CFLAGS", Value: join(cflags)},
		{Name: "CGO_CPPFLAGS", Value: join(cppflags)},
		{Name: "CGO_CXXFLAGS", Value: join(cxxflags)},
		{Name: "CGO_FFLAGS", Value: join(fflags)},
		{Name: "CGO_LDFLAGS", Value: join(ldflags)},

			return nil, fmt.Errorf("pkg-config --cflags: %w", err)
		}
		args = append(args, strings.Fields(string(out))...)
	}
	args = append(args, "-I", tmpdir)
	args = append(args, strings.Fields(os.Getenv("CGO_CFLAGS"))...)
	args = append(args, bp.CgoCFLAGS...)
	args = append(args, bp.CgoFiles...)

	cmd := exec.Command(args[0], args[1:]...)
	cmd.Dir = bp.Dir
	if err := cmd.Run(); err != nil {

	cgoCflags := os.Getenv("CGO_CFLAGS")
	if cgoCflags != "" {
		cgoCflags += " "
	}
	cgoCflags += "-I" + tmpdir

	cgoLdflags := os.Getenv("CGO_LDFLAGS")
	if cgoLdflags != "" {
		cgoLdflags += " "
	}
	cgoLdflags += "-L" + tmpdir + " -ltestgo2c2go"

	goenv := []string{"CGO_CFLAGS=" + cgoCflags, "CGO_LDFLAGS=" + cgoLdflags}

	cmd := exec.Command("go", subcommand)
	cmd.Args = append(cmd.Args, c.goFlags...)
	cmd.Args = append(cmd.Args, args...)
	replaceEnv(cmd, "CGO_CFLAGS", strings.Join(c.cFlags, " "))
	replaceEnv(cmd, "CGO_LDFLAGS", strings.Join(c.ldFlags, " "))
	appendExperimentEnv(cmd, experiments)
	return cmd
}

	tg.run("env", "GCCGO")
	tg.grepStdout(".", "GCCGO unexpectedly empty")

	tg.run("env", "CGO_CFLAGS")
	tg.grepStdout(".", "default CGO_CFLAGS unexpectedly empty")

	tg.setenv("CGO_CFLAGS", "-foobar")
	tg.run("env", "CGO_CFLAGS")
	tg.grepStdout("^-foobar$", "CGO_CFLAGS not honored")

	tg.setenv("CC", "gcc -fmust -fgo -ffaster")
	tg.run("env", "CC")
	tg.grepStdout("gcc", "CC not found")

//		from appearing in #cgo CFLAGS source code directives.
//		Does not apply to the CGO_CFLAGS environment variable.
//	CGO_CPPFLAGS, CGO_CPPFLAGS_ALLOW, CGO_CPPFLAGS_DISALLOW
//		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
//		but for the C preprocessor.
//	CGO_CXXFLAGS, CGO_CXXFLAGS_ALLOW, CGO_CXXFLAGS_DISALLOW
//		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
//		but for the C++ compiler.

	cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-buildmode=c-archive", "-o", ar, lib)
	env := []string{
		"CGO_ENABLED=1",
		"GOOS=ios",
		"GOARCH=arm64",
		"CC=" + strings.Join(CC, " "),
		"CGO_CFLAGS=", // ensure CGO_CFLAGS does not contain any flags. Issue #35459
		"CGO_LDFLAGS=" + strings.Join(CGO_LDFLAGS, " "),
	}
	cmd.Env = append(os.Environ(), env...)
	t.Logf("%q %v", env, cmd)

			}
		}

	case os == "aix", os == "android", os == "dragonfly", os == "freebsd", os == "linux", os == "netbsd", os == "openbsd":
		gt := cgoTest("external-g0", "test", "external", "")
		gt.env = append(gt.env, "CGO_CFLAGS=-g0 -fdiagnostics-color")

		cgoTest("external", "testtls", "external", "")
		switch {
		case os == "aix":
			// no static linking
		case p == "freebsd/arm":

permitted, notably alphanumeric characters and a few symbols, such as
'.', that will not be interpreted in unexpected ways. Attempts to use
forbidden characters will get a "malformed #cgo argument" error.

When building, the CGO_CFLAGS, CGO_CPPFLAGS, CGO_CXXFLAGS, CGO_FFLAGS and
CGO_LDFLAGS environment variables are added to the flags derived from
these directives. Package-specific flags should be set using the

	// documented (although coming up with a simple explanation of the
	// flag might be challenging). For more context see issues #58619,
	// #58620, and #58848.
	flagSources := []string{"CGO_CFLAGS", "CGO_CXXFLAGS", "CGO_FFLAGS"}
	flagLists := [][]string{cgoCFLAGS, cgoCXXFLAGS, cgoFFLAGS}
	if flagsNotCompatibleWithInternalLinking(flagSources, flagLists) {
		tokenFile := objdir + "preferlinkext"