Is there a build tool based on inotify-like mechanism

Question

In relatively big projects which are using plain old make, even building the project when nothing has changed takes a few tens of seconds. Especially with many executions of make -C, which have the new process overhead.

The obvious solution to this problem is a build tool based on inotify-like feature of the OS. It would look out when a certain file is changed, and based on that list it would compile this file alone.

Is there such machinery out there? Bonus points for open source projects.

Answer 1

You mean like Tup:

From the home page:

"Tup is a file-based build system - it inputs a list of file changes and a directed acyclic graph (DAG), then processes the DAG to execute the appropriate commands required to update dependent files. The DAG is stored in an SQLite database. By default, the list of file changes is generated by scanning the filesystem. Alternatively, the list can be provided up front by running the included file monitor daemon."

Answer 2

I am just wondering if it is stat()ing the files that takes so long. To check this here is a small systemtap script I wrote to measure the time it takes to stat() files:

# call-counts.stp

global calls, times

probe kernel.function(@1) {
    times[probefunc()] = gettimeofday_ns()
}

probe kernel.function(@1).return {
    now = gettimeofday_ns()
    delta = now - times[probefunc()]
    calls[probefunc()] <<< delta
}

And then use it like this:

$ stap -c "make -rC ~/src/prj -j8 -k" ~/tmp/count-calls.stp sys_newstat
make: Entering directory `/home/user/src/prj'
make: Nothing to be done for `all'.
make: Leaving directory `/home/user/src/prj'
calls["sys_newstat"] @count=8318 @min=684 @max=910667 @sum=26952500 @avg=3240

The project I ran it upon has 4593 source files and it takes ~27msec (26952500nsec above) for make to stat all the files along with the corresponding .d files. I am using non-recursive make though.