If you are using vendor libraries from Altera or Xilinx (ISE or Vivado), you do not need to set up these libraries by hand. Sigasi Studio has a Quick Fix to do this for you. The missing library will be added to the Common Libraries of your project.
library statement that tries to import a missing library (like
altera) will be have a yellow warning marker next to it. Click this
marker and select Configure library altera. If the path to your
Altera Quartus (or Xilinx ISE) installation is not yet set, Sigasi Studio will
ask to set the path now. You can always change these paths in Window
> Preferences > Sigasi > Toolchains.
Note that for the Xilinx libraries we only map the packages with the component declarations. By default all entity and architecture declarations are not mapped (excluded). This significantly reduces the time for a clean build. If you use direct entity instantiations, you can easily map the entities you need. See also Choose your version of the Vivado unisim.VCOMPONENTS package.
This rule can be disabled for your project, or its severity can be modified in the project linting settings.
Manual configuration in