unsetenv_c(key)
	if key == "GODEBUG" {
		godebugEnv.Store(nil)
		godebugNotify(true)
	}
}

// writeErrStr writes a string to descriptor 2.
// If SetCrashOutput(f) was called, it also writes to f.
//
//go:nosplit
func writeErrStr(s string) {
	writeErrData(unsafe.StringData(s), int32(len(s)))
}

// writeErrData is the common parts of writeErr{,Str}.
//
//go:nosplit

//	... set up y ...
//	systemstack(func() {
//		x = bigcall(y)
//	})
//	... use x ...
//
//go:noescape
func systemstack(fn func())

//go:nosplit
//go:nowritebarrierrec
func badsystemstack() {
	writeErrStr("fatal: systemstack called from unexpected goroutine")
}

// memclrNoHeapPointers clears n bytes starting at ptr.
//
// Usually you should use typedmemclr. memclrNoHeapPointers should be

	if !iscgo && !cgoHasExtraM {
		// There is no extra M. needm will not be able to grab
		// an M. Instead of hanging, just crash.
		// Cannot call split-stack function as there is no G.
		writeErrStr("fatal: bad g in signal handler\n")
		exit(2)
		*(*uintptr)(unsafe.Pointer(uintptr(123))) = 2
	}
	needm(true)
	if !sigsend(uint32(sig)) {
		// A foreign thread received the signal sig, and the