[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Automatic dependencies are out of sync
>>> On 06.09.18 at 09:34, <jgross@xxxxxxxx> wrote: > On 05/09/18 16:05, Juergen Gross wrote: >> I think we have a major problem in our build system regarding >> automatic dependencies. >> >> Starting with a new tree (after git clone or make clean) I have >> no dependency files (*.d2) anywhere: >> >> $ make clean >> $ find . -name '*.d2' | wc -l >> 0 >> >> Doing "make" will produce only some of them in a very limited number of >> directories: >> >> $ make >> $ find . -name '*.d2' | wc -l >> 279 >> $ find . -name '*.d2' | xargs -n 1 dirname | sort -u >> ./tools/firmware/xen-dir/xen-root/xen/arch/x86 >> ./tools/firmware/xen-dir/xen-root/xen/arch/x86/x86_64 >> ./tools/firmware/xen-dir/xen-root/xen/common >> ./tools/firmware/xen-dir/xen-root/xen/common/compat >> ./xen/arch/x86 >> ./xen/arch/x86/x86_64 >> ./xen/common >> ./xen/common/compat >> >> And only after the next "make" we have all of the *.d2 files available: >> >> $ make >> $ find . -name '*.d2' | wc -l >> 969 >> >> I guess the reason for that is that the *.d2 files only depend on the >> *.d files which are built together with the *.o files. They are not >> needed for building the product files, so they seem to be always one >> make step behind. >> >> Now comes the weird part (that's why I started to look into this): >> When I now do: >> >> $ touch tools/libxc/include/xenctrl.h >> $ make >> >> I get build failures in tools/tests/depriv (lots of unknown types like >> uint64_t). The .d file in the depriv directory suddenly contains only >> 7 instead of 44 entries, while the .d2 file is still okay (it is one >> make "older", do you remember?): >> >> $ wc .*.d* >> 7 14 546 .depriv-fd-checker.d >> 44 88 1923 .depriv-fd-checker.d2 >> >> And doing another make will succeed again, but now both dependency files >> are cut down to 7 entries (sure they are: .d2 is rebuilt from .d, while >> .d would only be rebuilt if .o is being built, which isn't happening as >> no file it depends on has changed): >> >> $ make >> $ wc .*.d* >> 7 14 546 .depriv-fd-checker.d >> 7 14 336 .depriv-fd-checker.d2 >> >> I have no immediate idea how to solve that. > > I've setup a little example Makefile solving the problem (just to show > the correct dependencies, needs to be adapted for naming the .d and .d2 > files and how to build the .d2): > > -->8 snip here 8<-- > > DEPS := tst.d2 > > all: tst $(DEPS) -include $(DEPS) already ought to have the effect of such a dependency, since all makefiles are checked for rules of how to re-make them. > %.d2: %.d > cp $< $@ Such a rule already exists in ./Config.mk. > %.o %.d: %.c > gcc -MMD -o $(patsubst %.c,%.o,$<) -c $< Doesn't this result in gcc to be invoked twice, perhaps resulting in corrupt .o and/or .d? I think %.d wants to depend on %.o, without a command. > %: %.o > gcc $< -o $@ > > -include $(DEPS) > > -->8 snip here 8<-- > > So the basic ideas are: > > - add a rule for constructing the .d files > - let the build depend on the .d2 files IOW I wonder whether this really is any different from what we do now (minus bugs/quirks in make itself, of course). And from this as well as your original mail I still don't understand what's actually broken with the current approach. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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