C and C++ library docs

[Roso Giuseppe \(Beppe\)]

Goodmorning, 
   I have to ask if someone know if there is a good documentation of Gnu C
   and C++ libraries documentation in postscript, acrobat pdf or something
   like format. I found only some old documents and often info or man
   aren't so complete.
   It is easier to find documentation on new X libraries (like GTK+ ...).

Thanks for any answers.

  Beppe