makefile

One of GNU make's many features allows you to shorten build times by running more than one command at a time. If your dependencies are all correct, or nearly correct, this can give you a significant improvement, and since it's built into the tool you get it "for free." But GNU make's parallel build feature—often called "dash j mode," after the command-line option that is used to enable it—is not without drawbacks. The worst of these is that GNU make parallel builds can produce incorrect results if the build dependencies are not sufficiently correct.