Makefile hierarchy: CFLAGS override-ability actually works now The original version was broken in that CFLAGS=${CFLAGS} passing was done without quotes, which breaks as soon as there is a space in the user-set CFLAGS. Changing it to CFLAGS="${CFLAGS}" makes it work as originally intended.

extern void serial_out();

void
putchar(ch)
{
	if (ch == '\n')
		serial_out('\r');
	serial_out(ch);
}