issue7978sync = 0
	go issue7978go()
	// test in c code, before callback
	issue7978wait(0, 1)
	issue7978check(t, "_Cfunc_issue7978c(", "", 1)
	// test in go code, during callback
	issue7978wait(2, 3)
	issue7978check(t, "test.issue7978cb(", "test.issue7978go", 3)
	// test in c code, after callback
	issue7978wait(4, 5)
	issue7978check(t, "_Cfunc_issue7978c(", "_cgoexpwrap", 1)