Spaces in filenames break most of make's builtin functions such as $(sort), and break the $?, $^ and $+ automatic variables. But they're OK in target names as l

Spaces in filenames break most of make's builtin functions such as $(sort), and break the $?, $^ and $+ automatic variables. But they're OK in target names as long as you escape the spaces with backslashes. In some cases you can also use them in source file names -- you have to hard code the names in the build rules since $^ won't work (but for targets built from a single source file, $< still does work). This applies to GNU make; not sure about AT&T make.