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Aleksei Sviridkin
d978a371a2
`.PHONY=a b c` and `.PHONY: a b c` differ in the `=` against the `:`, and only the second declares anything. The first defines an ordinary variable named `.PHONY` that nothing reads, leaving every listed target file-backed. A file or directory of that name beside a package Makefile then stands in as the product of the rule: for a target with no prerequisites make reports it up to date, skips the recipe and exits 0, and a target whose prerequisite is itself file-less keeps rebuilding until that prerequisite is shadowed too. The neighbouring `.DEFAULT_GOAL=help` is a real variable and is correct with `=`, so the two lines read alike while only one of them works, which is what let the inert form sit there unnoticed. Add hack/package-mk-phony.bats, six tests, picked up automatically by the hack/*.bats glob in `bats-unit-tests`. Three cover the declaration itself. The first reads the names off the `.PHONY:` line rather than repeating them, plants a file named after each beside a stub Makefile, and requires `make --dry-run` to print the recipe instead of "is up to date". A negative control mutates a copy back to the assignment form and requires the probe to report up-to-date, over the targets package.mk defines rather than the names it declares, because "is up to date" is only a meaningful answer for a name that has a rule. The third keeps those two sets equal: it requires the declared list and the defined targets to be the same set. Defined but undeclared is the direction the list rots in: check, clean, suspend and resume sat undeclared for as long as the declaration itself was inert. Declared but undefined is the empty-target trap in its general form, so a future name cannot slip in the way update and image once did. Two more pin what the list deliberately leaves out. package.mk defines neither `update` nor `image`; the including package Makefile does, and most packages define neither. Naming them here would create them as empty targets everywhere, turning "No rule to make target" into "Nothing to be done". Since the CI build matrix is parsed from the root Makefile `build:` target and runs `make -C <pkg> image` per unit, a package reaching that list without an `image:` rule would go from a red job to a green one that builds no image. One test requires that loud failure to survive, pinning both of the observables it is made of: make's exit status 2 and its diagnostic. They are independent, and a wrapper that kept the wording while returning something else would satisfy a check on the message alone. Its control extends the declaration with the two names in a copy and requires the failure to disappear, so the pin tracks the list rather than some property of the harness. Every decoy carries one fixed timestamp. Six of the nine targets take check as a prerequisite, and apply and delete reach it through suspend as well, so touching the decoys in list order can leave check newer than its own dependents. Make then rebuilds them for that reason and prints a recipe whatever .PHONY says, and the probe reports success against a declaration that does nothing. Equal mtimes remove the question in any list order. Measured on GNU Make 4.3: list order left the per-target assertion inert for up to six of the nine, moving with where the clock tick fell, while 3.81 fits the loop inside a single timestamp and shows none of it. The control test plants its decoys the same way for the same reason, and goes red if that is undone in its own loop. The two loops are independent, so neither guards the other, and the header is what keeps the arrangement from being unpicked. A sixth test leaves package.mk and covers the root Makefile, where this class had already bitten: `test` is the one target in the tree with a path of its own name beside it. It probes with --dry-run because the recipe wants a live cluster, and fails loudly if that path ever goes away rather than passing on a question with no subject. `%-update` is not coverable: .PHONY matches target names literally and does not expand patterns. Assisted-By: Claude <noreply@anthropic.com> Signed-off-by: Aleksei Sviridkin <f@lex.la>