Call graphs with bsd.obj.mk

[George Neville-Neil]

On Sep 5, 2012, at 11:28 , Jonathan Anderson <jonathan at FreeBSD.org> wrote:

> Hi all,
> 
> While doing some hacking recently, I really wanted a call graph. Clang
> and LLVM make this pretty easy, assuming you have the right CFLAGS, so
> a little build system integration seemed to be in order. I did this,
> it's pretty small and modular, and I find it useful, so I'm sharing
> this work with the list in the hope of putting it into -CURRENT.
> 
> I've attached two BSD makefiles that let me produce call graphs from
> any directory that includes bsd.obj.mk (which notably includes
> binaries and libraries in src):
> 
> - bsd.analysis.mk contains a 'callgraph' target that produces
> ${.OBJDIR}/_callgraph_.dot
> - bsd.llvm.mk contains a few LLVM helpers (e.g. to generate LLVM IR)
> 
> If you have clang, llvm-link and opt installed, this allows you to
> generate a complete call graph for C code; assembler files are ignored
> because we don't currently have assembly -> IR transformations. The
> resulting graph can be pretty large and ugly (e.g. LLVM shows an
> "external node" pseudo-function that calls everything), but it can be
> filtered with scripts like those found at
> https://github.com/trombonehero/dot-tools to produce really useful
> graphs.
> 
> llvm-link and opt aren't included in the bootstrap tools, so I'm
> currently doing this by installing the llvm-devel package. Perhaps we
> might copy llvm-link and opt over to /usr/obj/usr/src/tmp, possibly
> governed by a WITH_LLVM_TOOLS flag in src.conf or something?
> 

This would be great to have in the tree as a real build target.

Best,
George