mkrules: Apply object file dependencies to preprocessor targets. #17922
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #17922 +/- ##
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Coverage 98.38% 98.38%
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When using a preprocessing target like `make build/main.pp`, the target is not rebuilt when a header dependency has been modified. This improves but does not 100% fix the situation: If the object file has previously been built, the same dependency list for the object file is used for the preprocessor target as well. So for example, the following sequence in ports/unix will rebuild `main.pp` where it wouldn't before: ``` make build-standard/main.o # Create dependency information make build-standard/main.pp touch input.h make build-standard/main.pp # Rebuilds now, wouldn't have before ``` Signed-off-by: Jeff Epler <jepler@gmail.com>
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Summary
When using a preprocessing target like
make build/main.pp, the target is not rebuilt when a header dependency has been modified.This improves but does not 100% fix the situation: If the object file has previously been built, the same dependency list for the object file is used for the preprocessor target as well. However, building the
.pptarget does not update the dependency list, which could have changed.So for example, the following sequence in ports/unix will rebuild
main.ppwhere it wouldn't before:Testing
I locally used the
.pptargets and they behaved as I stated above.Trade-offs and Alternatives
It might be better to just make the
.pptargets.PHONYso that they're always re-made. They're quick enough, and the use case I'm aware of is for a developer who is explicitly invoking make for just that purpose.