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by indygreg2
1621 days ago
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I once helped maintain a nearly full featured implementation of make in Python (pymake) that grew out of the Firefox project. As much as I would like to support efforts like this, I feel like it is ultimately doomed to suffer from usability limitations because make does not have a static DAG. Rather, the DAG evolves dynamically as make evaluates targets. There are pesky problems like $(call) and $(eval) where you can dynamically inject make expressions into a partially evaluated DAG. And targets can generate files which are later loaded via include directives. Dumping the make database in a machine readable format (for visualization or otherwise) would be incredibly valuable for debugging and could improve understanding. But since many make files have N>>1 "snapshots" of the internal DAG during their execution, there is a really thorny problem around when and which of these "snapshots" to use and how to stitch them together. Many make files aren't "static" enough to support exporting a single, complete, and valuable usable snapshot of their internal DAG. If debugging is the target goal, I think a potentially better approach would be to define a function that takes an output filename and optional list of targets and writes out the point-in-time build graph when that function is called. This way makefile authors could insert probes in the make file (including at the bottom of a make file so the function is called on file load) and capture the state(s) of the build graph exactly when they need to. There could also be a specially named variable holding the names of targets that when pre- or post-evaluated would trigger the dumping of the database. Best of luck to the person doing this work. Debugging make is notoriously hard and any progress in this area will be much welcomed by its many users. |
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