Eclipse “Invalid project path: Duplicate path entries”

I have a Cplusplus project that is built using a makefile, Eclipse constantly warns about "Invalid project path: Duplicate path entries", but I cannot figure out what the hell it wants me to do. I would like to disable this warning and continue with my life.

My application compiles and runs fine, with not a single warning except this one. Being a conscientious developer I am keen to fix this problem so I have the warm fuzzies only a clean build can bring.

SOLUTION

1. Open the project properties | C/C++ Build | Discovery Options.
2. Click the button by Clear discovered entries now.
3. Rebuild.

It is seems to be a new feature in CDT. I have had this "Invalid project path: Duplicate path entries" problem for years, and this is apparently the newly provided solution.

Before doing this there were duplicate paths under C/C++ General | Paths and Symbols | Includes tab. I could not get rid of these. They only appear when Show built-in values is checked, so they are apparently generated somehow. After doing the above
they were replaced with a set that did not have duplicates. The only difference is that the same settings appeared under Assembly, GNU C, and GNU C++. Previously they were different sets. The ones for Assembly were empty, for example.

So far the problem has not returned.