Depending on your setup and the amount of build machines, you may have
even better results with sccache from Mozilla. It's a new implementation
similar to ccache with an optional distributed cache in S3 or Redis.
The downside is if you have long running tests in the list, it won't
help you much (unless you have a way to checksum the test programs and
skip them maybe?). But still, it's always a good thing to rerun them as
you may have some unstable tests and more runs means more confidence.
/Florent
On 22/05/2017 23:06, Craig Scott wrote:
I highly recommend Florent's suggestion. We use ccache on our CI
system and for local development. We've stopped worrying about how
long builds take now, since only files that are changed or that rely
on things that changed contribute any meaningful amount to the build
time. It also works for Make, Ninja and Xcode, so it's more flexible
than relying on some feature of Make and it is also pretty easy to set
up. You can set it up system wide, or you can take the approach
discussed in this article
<https://crascit.com/2016/04/09/using-ccache-with-cmake/> for systems
where you don't have access to set up ccache globally.
On Tue, May 23, 2017 at 4:54 AM, Florent Castelli
<florent.caste...@gmail.com <mailto:florent.caste...@gmail.com>> wrote:
On 22 May 2017, at 20:07, Robert Patterson via cmake-developers
<cmake-developers@cmake.org <mailto:cmake-developers@cmake.org>>
wrote:
We understand that CMake and make already can rebuild targets
which depend on changed files, and this behavior works exactly as
expected for us. Our issue is not that make is rebuilding targets
that it shouldn't. We would like this 'compile targets which
changed' behavior to work from a clean state, not just for
subsequent rebuilds. That is, from the first time cmake / make is
invoked, only the targets that depend on the given set of files
will be built, and no more.
When a developer submits a changeset to our continuous
integration tool, a fresh copy of the repository is checked out
by the worker at the commit of the changeset. We can access the
set of changed files from the commit data. Currently, cmake and
make correctly identify that the system is in a clean state and
that everything should be built if the current top-level target
is specified. This is the point where we would like our behavior
to differ. We want the rebuild changed targets behavior as if
everything were already built, but from this clean state.
Once we have determined the targets to build, we could simply
specify these targets as goals to make in the command line, but
we are hampered by the following limitation of make.
We are using GNU make 3.82. Invoking 'make -j target1 target2
target3' on the command line specifies the targets as goals to
make. If several goals are specified, 'make' processes each of
them in turn, in the order you name them.
https://www.gnu.org/software/make/manual/html_node/Goals.html
<https://www.gnu.org/software/make/manual/html_node/Goals.html>
Ninja does not currently work for our project.
It would be interesting to fix Ninja for your project then. Do you
know what isn’t currently working?
Also, Ninja has some APIs to expose all the dependency graph,
which you could probably query somehow to find out which target
you need to rebuild.
Another possibility, albeit a bit different, could be to use a
compilation cache to just rebuild everything but much faster, to
the point that it might not be relevant anymore.
/Florent
On May 19, 2017, at 2:32 AM, Simon Richter
<simon.rich...@hogyros.de <mailto:simon.rich...@hogyros.de>> wrote:
Hi,
On 18.05.2017 23:48, Robert Patterson via cmake-developers wrote:
My company has a large, predominately C++ codebase, with
hundreds of
targets, both for product and unit tests. In an effort to
improve the
compile and test time for developers, which utilizes a continuous
integration infrastructure, it is desirable to compile only the
targets
that are affected by developer's change sets.
Erm, it should already work this way. If Make rebuilds a target
that it
shouldn't, the first step would be investigating why it thinks the
target needs to be rebuilt.
Dependency tracking is one of the oldest problems, and cmake
should use
an appropriate solution for the actual build system you use. The
approach used for Make is a bit more conservative than you would
require
for GNU Make, but should nevertheless still work.
http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/
<http://make.mad-scientist.net/papers/advanced-auto-dependency-generation/>
is a good primer on dependency list generation with Make -- CMake
generates rules that are similar to these.
'make' has a limitation where if 'make target1 target2 target3' is
invoked, target1, target2, and target3 are built serially, not in
parallel.
Which version of make are you using?
Simon
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