Your example (with some tweaking) worked on my platform.
My platform is Cygwin / WinXPpro (NT 5.1sp1a) and GCC 3.3.1 (cygming special).
The tweaking should be immaterial. Things like putting in function bodies for String, changing #include <iostream.h> to #include <iostream>, adding in "std::" prefixes in the few spots they're needed, changing where top points to in the makefile.
Keep in mind that ctype.h is not part of GCC; it's supplied by your distribution (Slackware).
It appears that either your GCC was built for a different version of Slackware,
or... you have a filename collision (perhaps due to case insensitive filesystem?)
or... you could try putting #include <cctype> in your main.cc
Generally speaking, it's bad practice to name your project's header files the same as the system header files. Even if they differ in case, such as <ctype.h> versus "CType.h".
Try this: g++ -E -dI -c main.cc
That should show you if you are actually including the Slackware /usr/include/ctype.h as you expect. I suspect you are not getting what you think you should be getting.
Sincerely, --Eljay
