How to generate one large dependency map for the whole project that builds with makefiles?
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How to generate one large dependency map for the whole project that builds with makefiles?

I have a gigantic project that is built using makefiles. Running make at the root of the project takes over 20 minutes when no files have changed (i.e. just traversing the project and checking for updated files).

I'd like to create a dependency map that will tell me which directories I need to run 'make' in based on the file(s) changed. I already have a list of updated files that I can get from my version control system, and I'd like to skip the 20 minutes of traversing and get straight to the locations that do need to be recompiled.

The project has a mix of several languages and custom tools, so this would ideally be language-independent (i.e. it would only process all makefiles to generate dependencies). I'll settle for a C/C++-specific solution, too, as the majority of the project is in C++. The project is built on Linux.

[Edit - clarifications, responses to comments]

The project truly is gigantic, it's taking 20 minutes simply because of the size and because of all things described in the link below ("recursive makes consider harmful"). Unfortunately, the project is put together from many pieces coming from many different places, and there's little flexibility in what I can do with low-level Makefiles... the top-level ones putting the pieces together are the ones I have control over.

Why does mmap() fail with ENOMEM on a 1TB sparse file?


Library for parsing arguments GNU-style? [closed]
One thing you could look for is "makefile graph" -- there are a few projects out there to make dependency trees from large makefile projects. Setup SVN/LAMP/Test Server/ on linux, where to start? Here's one: . Best practice for C++ audio capture API under Linux? I think it will both create a pretty graph, and actually build things.. How to implement a timeout in read function call? If you want to roll your own Makefile parser, and essentially replace make with your own custom script, my advice would be "don't". Can my thread help the OS decide when to context switch it out? But there is a collection of Perl modules: Makefile::Parser. Why my linux signal handler run only once It claims to "pass 51% of the GNU Make test suite".. Cannot press QPushButton in a simple program If you want to just look at what's taking so long, you must turn on Make's debugging output. Bits of it are usually sort of useless, like the pages and pages of Make deciding whether or not to apply implicit rules, although maybe there will be any obvious thing this happens this doesn't need to happen. If you want to did this, you could look at remake, "GNU Make with comprehensible tracing and a debugger"..


If a simple make with no updates takes 20 minutes, this need be a huge project! Considering this your makefile configuration is OK you could try any thing like ccache.. notice this even if you receive the list of files you just need to comiple, you might still need to run make from the root of the project for the reason this the changes will have to be linked back into the main binaries. So if ccache is not good enough yet, and you insist in solving this problem yourself, you will still have to track which binary files you have to re-link again with "ld".

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