The calltree command parses a collection of input files (assuming C syntax) and builds a graph that represents the static call structure of these files.

Calltree is similar to cflow(1) but unlike cflow(1), calltree is not based on lint(1).Calltree implements some more functions than cflow(1), but does not list the return types of the functions. This is because calltree includes an own C parser and thus may be used even on systems that don't have lint(1).

The disadvantage is that the C parser that is used by calltree is not completely correct and may not find all calls of a function. This is mainly true for calls that are done via function pointers.

Calltree is able to detect recursive function calls (e.g. functions that call themselves). Recursive function calls are marked with an ellipsis in the output.