llvm dev - Aug 2020 - Ninja behavior that befuddles me

This morning I did a build with Ninja, which mysteriously decided to rebuild the
entire system (something about a deps stamp being corrupted). When it was done,
I had a new llvm-tblgen.exe, but all the target .inc files were old. Hmm. So I
touched one of the TableGen source files and did another build. Again, a new
llvm-tblgen.exe but no new .inc files. I do, however, have a new .inc.d file
corresponding to each .inc file.

I notice that those .inc.d files do not list llvm-tblgen.exe as a dependency. Is
that why the .inc files aren't rebuilt? If so, what is the trick?

----------------------------------------------------------------
Windfall               Paul C. Anagnostopoulos 
      ----------------------------------------------------------
   Software            978 369-0839
                             www.windfall.com
----------------------------------------------------------------
My life has been filled with calamities,
some of which actually happened.
---Mark Twain 

Guga 'mzimba, sala 'nhliziyo

Before replacing a file, tblgen checks whether its content is identical.
This keeps the time stamps from being updated without any change being made.

The command in add_custom_command is not made a file dependency. The idea
is that the command's input file determines the output file's content,
not
the algorithm that does it.

See
https://cmake.org/cmake/help/latest/command/add_custom_command.html#command:add_custom_command
> Whenever a target is used as a command to execute or is mentioned in a
generator expression as a command argument, a target-level dependency will
be added automatically so that the mentioned target will be built before
any target using this custom command. However this does NOT add a
file-level dependency that would cause the custom command to re-run
whenever the executable is recompiled. List target names with the DEPENDS
option to add such file-level dependencies.

Michael








Am Di., 11. Aug. 2020 um 10:39 Uhr schrieb Paul C. Anagnostopoulos via
llvm-dev <llvm-dev at lists.llvm.org>:
> This morning I did a build with Ninja, which mysteriously decided to
> rebuild the entire system (something about a deps stamp being corrupted).
> When it was done, I had a new llvm-tblgen.exe, but all the target .inc
> files were old. Hmm. So I touched one of the TableGen source files and did
> another build. Again, a new llvm-tblgen.exe but no new .inc files. I do,
> however, have a new .inc.d file corresponding to each .inc file.
>
> I notice that those .inc.d files do not list llvm-tblgen.exe as a
> dependency. Is that why the .inc files aren't rebuilt? If so, what is
the
> trick?
>
> ----------------------------------------------------------------
> Windfall               Paul C. Anagnostopoulos
>       ----------------------------------------------------------
>    Software            978 369-0839
>                              www.windfall.com
> ----------------------------------------------------------------
> My life has been filled with calamities,
> some of which actually happened.
> ---Mark Twain
>
> Guga 'mzimba, sala 'nhliziyo
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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I'm a total newbie as far as CMake and Ninja are concerned. How do I force
Ninja to build the target .inc files? I'm working on TableGen, so my changes
to the executable may indeed change the output files. I want to be sure they did
not, in fact, change.

Should I just touch all the .td files?

At 8/11/2020 12:01 PM, Michael Kruse wrote:
>Before replacing a file, tblgen checks whether its content is identical.
This keeps the time stamps from being updated without any change being made.
>
>The command in add_custom_command is not made a file dependency. The idea is
that the command's input file determines the output file's content, not
the algorithm that does it.
>
>SeeÂ
<https://cmake.org/cmake/help/latest/command/add_custom_command.html#command:add_custom_command>https://cmake.org/cmake/help/latest/command/add_custom_command.html#command:add_custom_command
>
>> Whenever a target is used as a command to execute or is mentioned in a
generator expression as a command argument, a target-level dependency will be
added automatically so that the mentioned target will be built before any target
using this custom command. However this does NOT add a file-level dependency
that would cause the custom command to re-run whenever the executable is
recompiled. List target names with the DEPENDS option to add such file-level
dependencies.
>Â 
>Michael
>
>Am Di., 11. Aug. 2020 um 10:39Â Uhr schrieb Paul C. Anagnostopoulos via
llvm-dev <<mailto:llvm-dev at lists.llvm.org>llvm-dev at
lists.llvm.org>:
>This morning I did a build with Ninja, which mysteriously decided to rebuild
the entire system (something about a deps stamp being corrupted). When it was
done, I had a new llvm-tblgen.exe, but all the target .inc files were old. Hmm.
So I touched one of the TableGen source files and did another build. Again, a
new llvm-tblgen.exe but no new .inc files. I do, however, have a new .inc.d file
corresponding to each .inc file.
>
>I notice that those .inc.d files do not list llvm-tblgen.exe as a
dependency. Is that why the .inc files aren't rebuilt? If so, what is the
trick?