Installation guide

– _align
– globaldef
– globalvalue
– noshare
– readonly
– variant_struct
– variant_union
• The DIGITAL UNIX C compiler does not support the main_program
option. On VAX ULTRIX systems, this option allows you to give the
main function a different name.
• To be compatible, DIGITAL UNIX C structure and union types must be
identical. The vcc compiler treats structure and union types as
compatible if they are the same size in bytes. The types need not be
identical to be compatible.
• The DIGITAL UNIX C compiler does not support applying the unary &
(address-of) operator to a constant in the argument list of a function
call. The vcc compiler supports this use of the & operator.
• The DIGITAL UNIX C compiler replaces comments that separate
tokens in a macro definition with one space character during
preprocessing. Therefore, you cannot use a comment as a concatenation
character on DIGITAL UNIX systems.
On VAX ULTRIX systems, comments that separate tokens within a
macro definition are deleted with no spaces. This action allows you to
use a comment as a concatenation character.
On DIGITAL UNIX systems, replace a comment that you use as a
concatenation character with the ANSI-defined concatenation
characters (##).
• On DIGITAL UNIX systems, you can redefine a macro only if the token
you use in the new macro definition is identical to the token you used in
the existing macro definition. The vcc compiler allows you to redefine
macros.
• The DIGITAL UNIX C and vcc compilers use a different algorithm for
substituting macro definitions. These different algorithms might cause
you to notice differences in how your macros are processed on a
DIGITAL UNIX system.
• By default, the DIGITAL UNIX C compiler links your application with
shared libraries, instead of archive libraries. If you want your
application to be linked with archive libraries, use the −non_shared
option. For more information, see Section 8.1.
Migrating Your ULTRIX Application to a DIGITAL UNIX System 7–33