Re: [libtool] make install fails after an incremental build after a prefix change?

[Gavin Smith]

On 29 December 2015 at 19:52, Kees-Jan Dijkzeul <address@hidden> wrote:
> Either would obviously work, but kind of defeat the purpose of having
> incremental builds, and unnecessarily  load the buildserver. A
> solution where I could do an incremental build after a configure
> incantation would be much preferred.
>
> Note that this already seems to work well for configure incantations
> that modify config.h :-)

You want not to rebuild files that don't need to be rebuilt. Depending
on config.h doesn't achieve this: any source files including it will
have to be compiled again. If most of the source files do include
config.h, they'll all be rebuilt and it won't be much quicker to avoid
running "make clean" first.

Running configure changes the Makefile, and I believe that this is a
difficult problem to solve to know what has to be rebuilt in this
case. A similar problem is directly editing a Makefile to change the
flags being passed to the compiler: when you re-run "make", it doesn't
know that the flags have changed and the compiler won't be run again,
even though it should be. As long as "make" is being used to know what
depends on what, what would be needed in such a case would be for the
facts that change to be in a separate file that the Makefile refers to
and that "make" could see has changed. I expect that's difficult to
achieve with changing the installation directories.