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Warn that Bazel's defines are transitive (for discussion) - #57
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CMake scopes a compile definition to a target (PRIVATE) or its consumers (PUBLIC/INTERFACE). Bazel's `defines` always propagate to every dependent; the equivalent of PRIVATE is `local_defines`. The per-TU diff only checks that each TU gets the defines CMake gave it, so a PRIVATE define written as `defines` converges while changing how every consumer compiles (a visibility macro such as <target>_EXPORTS turning on export-side behavior in consumers is the classic case). The only signal would be a WARN-level extra define on each consumer's TUs. Observed in any2bazel-lab: a lensfun migration avoided this unprompted, putting its visibility and <target>_EXPORTS defines in local_defines for exactly this reason. No run has yet been seen getting it wrong, so there is no evidence the skill needs the line. Adds one sentence to "Create initial BUILD.bazel files". In the lab's later lensfun run with this change, the agent again kept those defines in local_defines. This is a proposal for discussion: it costs a line of context in every run to prevent a mistake not yet observed. Lab-Proposal: P7 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Part 22 of 23 of a stacked series (tracking issue: #35). Based on
D4-long-commands, the previous part: review and merge that first.Kind: discussion. Lab proposal: P7.
What the migration runs showed
definespropagate to dependents where CMake'sPRIVATEdefinitions do not. With the warning, the lensfun run kept<target>_EXPORTSand visibility defines inlocal_defines(run 083).The change
CMake scopes a compile definition to a target (PRIVATE) or its consumers
(PUBLIC/INTERFACE). Bazel's
definesalways propagate to every dependent;the equivalent of PRIVATE is
local_defines. The per-TU diff only checksthat each TU gets the defines CMake gave it, so a PRIVATE define written as
definesconverges while changing how every consumer compiles (avisibility macro such as _EXPORTS turning on export-side behavior
in consumers is the classic case). The only signal would be a WARN-level
extra define on each consumer's TUs.
Observed in any2bazel-lab: a
lensfun migration avoided this unprompted, putting its visibility and
_EXPORTS defines in local_defines for exactly this reason. No run
has yet been seen getting it wrong, so there is no evidence the skill needs
the line.
Adds one sentence to "Create initial BUILD.bazel files". In the lab's later
lensfun run with this change, the agent again kept those defines in
local_defines.
This is a proposal for discussion: it costs a line of context in every run
to prevent a mistake not yet observed.
Testing
pytest tests/at this commit: 196 passed (130 onmain).🤖 Generated with Claude Code