pthreads infection

[Matěj Týč]

Hello,
if I link to a library that uses pthreads (for example OpenEXR suggests
the -pthreads LDFLAG -- taken from OpenEXR.pc pkg-config file), I can
see that unlike library dependencies this dependency propagates further
like some disease. Even if my product is a library or a module, not only
that I have to provide the -pthreads LDFLAG during (library / module)
compilation, but the app (that uses the produced library / opens that
module) also has to be linked with the -pthread LDFLAG.
The problem is that libtool doesn't seem to discover this problematic
dependency and forgets to add the appropriate flag to the app that is
known to use the library (that uses the -pthreads flag) when the
library's .la file is present. Is this a bug that can be fixed, or does
it have some "normal solution"?
However, in a case of a module, there is generally no way that I can
determine whether my app will have to open such pthreads-infected
module.
Therefore I could add the -pthread flag as some "prevenive measure", but
it is not quite portable, is it?
I have took a look at gnulib and AFAIK it doesn't address this issue
either. I think that I am supposed to use mthreads on Windows or
something like that.
Any suggestions?
Regards,
Matej