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9.6 Testing the Compilation of a Program

Normally, when an error happens in executing a shell command, make gives up immediately, returning a nonzero status. No further recipes 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.