Add DEPENDS_EXPLICIT_ONLY to remove implicit dependencies #910
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Signed-off-by: Anthony Welte <[email protected]>
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Signed-off-by: Anthony Welte <[email protected]>
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I've updated the PR and tested on rhel9 and Ubuntu 24.04. The options is only used on Ubuntu (with cmake 3.28), on rhel9 the behavior is unchanged. |
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lgtm. this will track only the listed dependencies in DEPENDS list, so that i can reduce possible spurious rebuilds due to inferred dependencies.
@InvincibleRMC @gavanderhoorn WDYT?
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I'm no expert of cmake but from my understanding this looks good. |
| DEPENDS ${target_dependencies} | ||
| COMMENT "Generating type hashes for ROS interfaces" | ||
| VERBATIM | ||
| ${_dep_explicit_only} |
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I actually did but it doesn't work. I tried setting it to $<$<VERSION_GREATER_EQUAL:${CMAKE_VERSION},3.27>:DEPENDS_EXPLICIT_ONLY> but it's treated as just another argument to the previous option. Also tried to use it to set the variable (set(_dep_explicit_only "$<$<VERSION_GREATER_EQUAL:${CMAKE_VERSION},3.27>:DEPENDS_EXPLICIT_ONLY>")) but it also didn't work.
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Description
This PR addresses one of the build speedup mentioned in #859.
When
add_custom_commandis used to generate files that are then used by a target, theadd_custom_commandbecomes implicitly dependent on the target dependencies. In rosidladd_custom_commandis used to generate files from the IDL files, the generator does not depend on anything else (except rosidl_generator_c[pp] whose generators depend on rosidl_generator_type_description).This PR (and the equivalent for rosidl_typesupport, rosidl_typesupport_fastrtps and rosidl_python) adds the
DEPENDS_EXPLICIT_ONLYoption of add_custom_command to most generators (except for C/CPP).Note
This option is only useful when using Ninja. When testing use
--cmake-args -GNinjaSince the generators are no longer constrained by unnecessary dependencies, they can start immediately. This speeds up the build significantly (2x for px4_msgs on my machine).
Warning
DEPENDS_EXPLICIT_ONLY requires cmake 3.27. The version that ships with Ubuntu 24.04 is 3.28, not sure about other supported distributions.
Right now I've bumped the required version to 3.27 but I could instead only add the option when the cmake version is sufficient (if that's preferable ?).Note
I wanted to also add the option to rosidl_generator_c[pp] and explicitly specify the dependency to rosidl_generator_type_description. I couldn't figure out how to make it work.
Is this user-facing behavior change?
Did you use Generative AI?
no
Additional Information
I've already created PRs for the other packages. I've set then to Draft until this PR is reviewed.