Re: [PATCH 2/3] cmake: create compile_commands.json by default

On Fri, Jun 4, 2021 at 5:09 PM Sibi Siddharthan
[off-list ref] wrote:

On Fri, Jun 4, 2021 at 11:13 PM Matthew Rogers via GitGitGadget
[off-list ref] wrote:

quoted

A straightforward way to accomplish this is to make it as simple as
possible is to enable the generation of the compile_commands.json file,
which is supported by many tools such as: clang-tidy, clang-format,
sourcetrail, etc.

This does come with a small run-time overhead during the configuration
step (~6 seconds on my machine):

    Time to configure with CMAKE_EXPORT_COMPILE_COMMANDS=TRUE

    real    1m9.840s
    user    0m0.031s
    sys     0m0.031s

    Time to configure with CMAKE_EXPORT_COMPILE_COMMANDS=FALSE

    real    1m3.195s
    user    0m0.015s
    sys     0m0.015s

This seems like a small enough price to pay to make the project more
accessible to newer users.  Additionally there are other large projects
like llvm [2] which has had this enabled by default for >6 years at the
time of this writing, and no real negative consequences that I can find
with my search-skills.

The overhead is actually much smaller than that. In my system it is
less than 150ms.

Is that 150 ms for the whole process or just the difference between the two
options?  I'm running this on windows via the git bash provided by the
git sdk.

The first configure takes this long because we generate command-list.h
and config-list.h.
This process is really slow under Windows.

I used two different build directories for both my invocations specifically
to avoid having to account for cache variables and other side effects
from earlier configurations.  The variation could also be from network
latency since in this test I was downloading vcpkg, etc.

Thank You,
Sibi Siddharthan

-- 
Matthew Rogers