cdepend is a utility, which analyzes a project in C language. Its output is a mapping of which C function calls which. cdepend works on projects consisting of several source files.
This utility can be very useful when porting C code from UNIX to an environment which is not as rich with library functions, since the dependency on these functions is easily tracked down.
Also, cdepend makes a list of unused functions, and functions that are not declared. For each function you also get a detailed report file, saying where the function is called (file and row number). It's also easy to get a picture of which library functions the project relies on.
All this is accomplished by reading the assembly code, which gcc creates when invoked with the -S flag. Hence, the entire project needs to be recompiled to generate the necessary data for cdepend.
More about the project (and download):
The current release is an early Alpha stage, and is expected to work on recent i386-Linux distros.
The project is licensed under GPL.
Hope you like it, Eli