Re: precompiled header suggestion

[Tom Tromey]

>>>>> "adl" == Alexandre Duret-Lutz <address@hidden> writes:

adl> This sounds tricky.  Adding such a file as a dependency of each .o file
adl> means that _all_ of them will be updated whenever the .ghc changes.

Good point.  There are other possible approaches, though.

For instance, for a given program, we could generate:

    am--program:  $(program_BUILT_SOURCES)
        $(MAKE) program

... which is sort of like the BUILT_SOURCES implementation, but more
targeted.

That's sort of backward, since "make program" will no longer work as
expected.  But you get the idea...

I suppose this is sort of secondary, and the main thing is just to
have some automation for building the .gch file at all.

adl> Putting the .ghc in BUILT_SOURCES automatically will not work if
adl> the .ghc includes another BUILT_SOURCES indirectly (direct
adl> inclusion is ok because we can issue the dependency ourself).
adl> Maybe we can live with such a limitation?

Yeah, there could be some problems here.  But the user can always add
an explicit dependency (just adding the .h to the gch file's _SOURCES
would suffice).

adl> Also I presume some libraries will also want to install such
adl> files?  Can they be installed?  (Is this what install-pch is
adl> about in your libstdc++ quote?)  If so, such installation also
adl> needs to be conditional.

Honestly, I don't know too much about this.  I'd suggest we leave
open the possibility that they can be installed, though.

adl> Maybe it would be simpler to introduce a new primary

Yeah.  Another idea would be to recognize `*.gch' automatically in a
_SOURCES variable corresponding to a program or library.

Tom