Normally, when an error happens in executing a shell command, make
gives up immediately, returning a nonzero status. No further commands are
executed for any target. The error implies that the goal cannot be
correctly remade, and make reports this as soon as it knows.
When you are compiling a program that you have just changed, this is not
what you want. Instead, you would rather that make try compiling
every file that can be tried, to show you as many compilation errors
as possible.
On these occasions, you should use the ‘-k’ or
‘--keep-going’ flag. This tells make to continue to
consider the other prerequisites of the pending targets, remaking them
if necessary, before it gives up and returns nonzero status. For
example, after an error in compiling one object file, ‘make -k’
will continue compiling other object files even though it already
knows that linking them will be impossible. In addition to continuing
after failed shell commands, ‘make -k’ will continue as much as
possible after discovering that it does not know how to make a target
or prerequisite file. This will always cause an error message, but
without ‘-k’, it is a fatal error (see Summary of Options).
The usual behavior of make assumes that your purpose is to get the
goals up to date; once make learns that this is impossible, it might
as well report the failure immediately. The ‘-k’ flag says that the
real purpose is to test as much as possible of the changes made in the
program, perhaps to find several independent problems so that you can
correct them all before the next attempt to compile. This is why Emacs'
M-x compile command passes the ‘-k’ flag by default.