[cmake] Keep dictionary byproducts newer than the generated .cxx - #23432
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guitargeek merged 1 commit intoSep 21, 2026
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The Makefile generator models each secondary output of the multi-output dictionary custom command (the _rdict.pcm, the .rootmap, the C++ module) as its own rule ending in 'cmake -E touch_nocreate <output>', to keep it newer than the primary output, the generated dictionary source. When a dictionary is regenerated through freshly re-scanned dependency information (make's depend/build phase split), those rules are not re-evaluated after the recipe has run: the byproducts stay older than the .cxx until the next build. That next build then fires the deferred touch, which rewrites the byproducts' mtimes in a build that had nothing to do (caught by the CI spurious-rebuild check) and spuriously regenerates every dictionary that consumes them. Do the touch in the dictionary recipe itself, right after rootcling, so the expected output ordering holds whenever the recipe runs, independent of the generator. 🤖 Done with the help of AI Closes root-project#20907.
Test Results 23 files 23 suites 3d 15h 48m 11s ⏱️ For more details on these failures, see this check. Results for commit 7040810. |
dpiparo
approved these changes
Sep 21, 2026
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The Makefile generator models each secondary output of the multi-output dictionary custom command (the _rdict.pcm, the .rootmap, the C++ module) as its own rule ending in 'cmake -E touch_nocreate ', to keep it newer than the primary output, the generated dictionary source. When a dictionary is regenerated through freshly re-scanned dependency information (make's depend/build phase split), those rules are not re-evaluated after the recipe has run: the byproducts stay older than the .cxx until the next build. That next build then fires the deferred touch, which rewrites the byproducts' mtimes in a build that had nothing to do (caught by the CI spurious-rebuild check) and spuriously regenerates every dictionary that consumes them.
Do the touch in the dictionary recipe itself, right after rootcling, so the expected output ordering holds whenever the recipe runs, independent of the generator.
🤖 Done with the help of AI
Closes #20907.