This might sound like a sci-fi feature request but I wonder if Doxygen has any of the two following features:

1. Generating the call/caller graphs after preprocessor ran over the input file.
Example:  

```
#define MULTITHREADING 1

```

and then blocks of code are enabled or disabled depending on whether `MULTITHREADING` is enabled.
2. Describing the *certainty of the call* with graph arrows... for example a dotted line if the function isn't always called (a.k.a it is in a branch or you have possible `return` before the function is called.