This appendix describes known problems and restrictions for the Class Library. Please note that String Package, which is part of the Class Library, is entirely different from the String class that is part of the newly-implemented C++ Standard Library and known as the String Library. Do not confuse these two contrasting implementations.

The following restrictions apply for the C++ Class Library:

• Conflict with redefinition of clear()
  If your program includes both <curses.h> and <iostream.hxx>, Compaq C++ might fail to compile your program because clear() is defined by both header files. In <curses.h>, clear() is defined as a macro whereas in <iostream.hxx> clear() is defined as a member function.
  Workarounds:
  If your program does not use either clear() or uses the <curses.h> clear(), include the <iostream.hxx> header first, followed by <curses.h>.
  If your program uses the ios::clear() function, undefine the clear() macro directly after the #include <curses.h> statement.
• Because of a bug in the task package, if you are using that package and you compiled your application with Compaq C++ Version 6.n, your application may encounter runtime errors such as segmentation faults. To avoid these problems, recompile your application specifying the -preempt_symbol option. For more information about the -preempt_symbol option, see the cxx(1) reference page.
• Use of clog() and the iostream package's clog
  A single application is restricted from using both the math library function clog() and the iostream package's clog object. This restriction is necessary because libm and libcxx each contain a definition for the global symbol clog and these definitions are incompatible.
  For example, consider a program that makes use of the iostream clog object:

  #include <stdlib.h> #include <iostream.hxx> int main() { clog << "abc"; return EXIT_SUCCESS; }

  
  If you link with the math library first as:

  cxx clog.cxx -lm -lcxx

  
  Executing the program results in a segmentation fault. The compiler links against shared object libraries by default. Identical symbols in subsequent object libraries are resolved to the first definition by the symbol preemption feature. So in this case use of clog from iostreams is resolved to the definition in libm.
  If you link -non_shared with the math library first as:

  cxx clog.cxx -non_shared -lm -lcxx

  
  The linker gives a multiply defined message similar to the following:

  ld: /usr/lib/cmplrs/cxx/libcxx.a(iostream_globals.o): clog: multiply defined

  
  In this case, if you link with the Class library first, the program executes correctly. As described earlier, the compiler links against shared object libraries by default. Identical symbols in subsequent object libraries are resolved to the first definition by the symbol preemption feature. So in this case use of clog from iostreams is resolved to the definition in libcxx:

  cxx clog.cxx -lcxx -lm

  
  Therefore, applications that reference either of the clog symbols should not include both -lcxx and -lm on their ld command line.

• Displacing global operator new in C++ Standard Library/Class Library
  If a C++ program defines a global operator new() which is intended to displace the version used by the C++ Standard Library, it must be compiled with the compiler command line switch -stdnew. If a C++ program defines a global operator new() which is intended to displace the version used by the C++ Class Library, it must be compiled with the compiler command line switch -nostdnew.
• The Class Library does not include support for 128-bit long doubles.

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