ben.boeckel added inline comments.
================ Comment at: clang/test/ClangScanDeps/P1689.cppm:155 +// CHECK-MAKE: [[PREFIX]]/impl_part.o: +// CHECK-MAKE: [[PREFIX]]/impl_part.cppm ---------------- ben.boeckel wrote: > ChuanqiXu wrote: > > ben.boeckel wrote: > > > ChuanqiXu wrote: > > > > ben.boeckel wrote: > > > > > For scanning, this cannot be the object file. The output needs to be > > > > > the P1689 output (or whatever the "main output" for the scanning rule > > > > > is). This is the purpose behind the `-MT <target>` flag: to say what > > > > > goes in this slot. I think it'll be necessary here (even if > > > > > `clang-scan-deps` learns an `-o` flag because it is the build system > > > > > that determines the "primary output"). > > > > > > > > > > I don't know if the `-MMD` and `-MD` differences are important or > > > > > not; I don't think I particularly care which is default (I've used > > > > > `-MD` FWIW), but it may matter for other situations. > > > > I am confused since the output `[[PREFIX]]/impl_part.o` is the same > > > > with `P1689` output `[[PREFIX]]/impl_part.o` and the one in the > > > > compilation database and the one specified in the command line option > > > > `--p1689-targeted-output`. What's the expected output for you in this > > > > case? (and the related command line input.) > > > P1689 is about specifying dependencies of *another* rule found by the > > > dynamic content of some source. `-MF` is about *discovered* dependencies > > > of *this* rule. > > hmmm sorry, I don't understand it a lot. May you explain your expectation > > in the form of the input and the corresponding output? > *This* rule outputs `foo.ddi` (in CMake terms). We need to tell make or ninja > what files, if they change, *this* rule needs rerun for. That is what `-MF` > is for. What I need is spelled `-MT` "normally". > > P1689, what this rule is *doing*, is writing dependencies for the *compile* > rule, so it is hooked up by *its output*. Two rules cannot have the same > output, so P1689 and `-MF` have completely different things to put for their > "output". > > You can see here: > https://gitlab.kitware.com/cmake/cmake/-/blob/master/.gitlab/ci/cxx_modules_rules_gcc.cmake > where `-MT` gets the `<DYNDEP_FILE>` which is the `-fdep-file=` argument. > `-fdep-file=` tells GCC what rule the P1689 itself is for. > -fdep-output= tells GCC what rule the P1689 itself is for. Fixed. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D139168/new/ https://reviews.llvm.org/D139168 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
