[CMake] DESTDIR behaviour with different variable name

[Tomasz Grobelny]

On Monday 11 April 2011 21:55:48 Alexander Neundorf wrote:
> On Monday 11 April 2011, Tomasz Grobelny wrote:
> > On Mon, 11 Apr 2011 09:01:09 -0700, Tyler <tyler at cryptio.net> wrote:
> > > On Mon, Apr 11, 2011 at 8:54 AM, Tomasz Grobelny
> > > 
> > > <tomasz at grobelny.oswiecenia.net> wrote:
> > >> Ok, but is there a way to achieve the same effect so that the user can
> > >> type just "make install" and not know anything about DESTDIR
> > environment
> > >> variable (provided he knows about MYDESTDIR)? Maybe it is possible to
> > >> put this "DESTDIR=$MYDESTDIR" in the generated Makefiles somehow...
> > > 
> > > If I understand your use case right (which I might not as you haven't
> > > described what you're trying to do, just how you're trying to do it),
> > > maybe you can just override CMAKE_INSTALL_PREFIX.
> > > 
> > > If you go this route, check the archives because of the whole
> > > _INITIALIZED_TO_DEFAULT aspect of that particular cache variable.
> > 
> > I already tried playing with CMAKE_INSTALL_PREFIX but the problem was
> > that value of MYDESTDIR was read (and saved to CMAKE_INSTALL_PREFIX)
> > only when configuring first time. That's why DESTDIR mechanism comes
> > closer to what I'm trying to achieve. My use case is something like
> > that:
> > 1. User has some default MYDESTDIR to non writable location.
> > 2. User executes "cmake . && make install".
> > 3. The installation fails because user has no rights to $MYDESTDIR.
> > 4. User changes MYDESTDIR to another location (writable this time).
> > 5. User executes "make install" once again and it should succeed.
> > 
> > Of course the user could set MYDESTDIR to correct location before
> > building but people often forget that. Now the tricky part is that users
> > are already used to this mechanism (for particular variable name, called
> > MYDESTDIR here). So taking different environment variable instead of
> > DESTDIR would allow me to minimize confusion among users. Otherwise I'll
> > just tell them to set yet another variable (DESTDIR). But I would like
> > to avoid that if at all possible.
> 
> DESTDIR has a different purpose.
> Installing to DESTDIR does not necessarily lead to a working and correct
> installation, mainly when paths are involved, like e.g. RPATH settings.
> Assuming that CMAKE_INSTALL_PREFIX would be /opt/foo, your executable might
> get /opt/foo/lib as RPATH, also when installed to $DESTDIR/opt/foo.
> So they will not have a correct RPATH.
> You really should set CMAKE_INSTALL_PREFIX.
> 
I'd like to. But CMAKE_INSTALL_PREFIX does not get recomputed when I change 
MYDESTDIR and try to do "make install" again. Or at least I don't know how to 
make it behave this way.
Besides, I don't use RPATH (at least not explicitely, hopefully cmake is not 
doing anything nasty behind the scenes).
-- 
Regards,
Tomasz Grobelny