[lldb-dev] Circular library dependencies

[Zachary Turner]

Trying to look at ways to reduce the link time of LLDB, I wrote a small
python script last night whose purpose is to get a rough idea of what
LLDB's dependency graph looks like.  A lot of this is CMake specific, but
the idea isn't much different either way.

It does this by walking the source and incldue folder.  For each folder
entered, it determines what .a this compiles to by looking for the
corresponding CMakeLists.txt and doing a rudimentary parse.

Then, for each .cpp and .h file found, scan the file for #include
statements, and map the include file to the corresponding location under
the source tree, using this to determine which .a file the #include is a
primary member of.  For each of these found, add that .a file to the list
of dependencies for the containing .a.

Basically what I found is that every folder more or less depends on every
other folder, which is pretty unfortunate.

I have some ideas about how to make some improvements, but I want to see
what people think first.  Aside from the obvious benefits of just making
the code be better layered and more separable, it also would reduce link
times quite a bit I think.  And there are lots of cases such as lldb-server
or unit tests where we want to link in as little as possible, as opposed to
the monolithic LLDB executable which wants to link in pretty much
everything.

Thoughts?
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