"error: visibility attribute not supported" in Cygwin/Windows7

[Bernd Prager <bernd@xxxxxxxxx>]

All,

I am struggling with the visibility attribute on Cygwin 1.7, Windows7 
and g++ (GCC) 4.5.3..
I have set "CXXFLAGS= -fvisibility=hidden". Nevertheless compilation 
fails with:

error: visibility attribute not supported in this configuration; ignored

I even tried to set "#pragma GCC visibility push(hidden)" in the source 
code, to no effect.

Any help or advice is appreciated.
Thank you,
-- Bernd