[CMake] -fPIC flag on object build for static lib targets?

[James Mansion]

>Are you trying to link object files compiled without -fPIC into a shared
>library?  That would never work; -fPIC is required for all objects in
shared
>libraries.

I'm guessing so - I want to do it too!  Or rather, be able
to make a static library containing objects that can be linked
to create a shared library - I think some people call it a
'convenience library'.

If you are building a number of dynamic libraries and some
sources are common - and you don't want to ship them in their
own dynamic library - then its useful.  It can also just be
used to keep the source tree and its sub-projects nicely
modular.  And it can be used to work around insanely long
command lines for linkers etc - I think libgcj uses them
like this (and last time I tried, it fell foul of the command
line length limit on FreeBSD if you didn't, though that was a
little while ago).

I don't think its an odd thing to do.

Example: suppose I have a C++ library that I'll build as a
DLL that wraps zlib, expat, and pcre.  PoCo does this, in fact,
using copies of sources from those libraries in the PoCo tree.
The resulting DLL does not expose the normal exports for those
libraries though - they are private.

It would be nice to be able to build (with CMake) the zlib,
expat and pcre libraries so that they can be kept seperate,
and yet built into the DLL without creating exports, as the
PoCo build does now.

James