I'm search for a tool that could compare source codes for similarity.

We have a very trivial system right now that has huge amount of false positives and the real positives can easily get buried in them.

My requirements are:

• reasonably small amount of false positives
• good detection rate (yeah these are going against each other)
• ideally with a more complex output than just a single value
• usable for C (C99) and C++ (C++03 and optimally C++11)
• still maintained
• usable for comparing two source files against each other
• usable in non-interactive mode

EDIT:

To avoid confusion, the following two code snippets are identical and should be detected as such:

for (int i = 0; i < 10; i++) { bla; }

int i; while (i < 10) { bla; i++; }

The same here:

int x = 10; y = x + 5;

int a = 10; y = a + 5;