Installation guide

indicate that symbols are defined more than once. The cc compiler on
VAX systems allows you to specify the same source or object file twice.
• 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.
• The DIGITAL UNIX cc command uses a different syntax for the asm
pseudofunction call.
• On DIGITAL UNIX systems, the −L option to the cc command operates
only on the −l options that follow it. On VAX systems, the cc −L option
affects all −l options. If you want the −L option to affect all −l options
on the command line when you use the DIGITAL UNIX C compiler,
specify the −L option first.
• The DIGITAL UNIX C compiler does not support the −R option
(read-only text).
• The DIGITAL UNIX Version 2.0 and earlier systems support two levels
of profiling that you use by running the postprocessor pixie utility.
Profiling on VAX systems has two levels that you select with the −p and
−pg options. The DIGITAL UNIX Version 3.0 system supports these
levels of profiling, as well as the pixie utility.
• The DIGITAL UNIX C compiler supports five levels of optimization,
which are controlled using the −O option. The C compiler on VAX
systems supports only one level of optimization, which is disabled by
default and enabled with the −O option.
By default, the DIGITAL UNIX C compiler optimizes as if you specified
the −O1 option. The optimization that the compiler performs is similar
to the optimizations performed by the cc command on a VAX system.
You disable optimizations by specifying the −O0 option when you use
the DIGITAL UNIX C compiler.
• The DIGITAL UNIX C compiler offers four levels for debugging
information (controlled by the −g option). The C compiler on VAX
systems has only two (on and off).
• Both the DIGITAL UNIX C compiler and VAX cc command support the
−t and −B options for specifying passes and paths. However, the
DIGITAL UNIX C compiler has more pass names. In addition, the
DIGITAL UNIX C compiler option −h is equivalent to the VAX cc
compiler option −B. The −B option to the DIGITAL UNIX C compiler
specifies a suffix for the pass name.
Migrating Your ULTRIX Application to a DIGITAL UNIX System 7–31