Installation guide

• 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 two
levels of profiling as well as the pixie utility.
• The DIGITAL UNIX C compiler supports five levels of optimization,
which are controlled by using the −O option. The vcc compiler 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 the compiler performs is similar to the
optimizations performed by the vcc command. 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 vcc compiler has only
two (on and off).
• Both the DIGITAL UNIX C compiler and the ULTRIX vcc 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
vcc compiler option −B. The −B option to the DIGITAL UNIX C
compiler specifies a suffix for the pass name.
• The DIGITAL UNIX C compiler does not produce a listing that contains
the source code, symbol table, machine code, and cross-reference
information.
7.5 Running lint to Find Other Errors
After you create object files for your application, use the lint command to
find other problems. The lint command gives you information about
whether you use data types correctly in your application, whether you use
routines and variables correctly, whether there are any 64-bit migration
problems, and so on.
The −Q option is included as support for migrating ULTRIX applications to
the DIGITAL UNIX system by identifying those programming techniques
that might cause problems on a 64-bit DIGITAL UNIX system. The
techniques identified include: pointer alignment; pointer and integer data
type combinations; assignments that cause a truncation of long data types;
assignments of long data types to another type; structure and pointer
combinations; type castings; and format control strings in scanf and
printf calls.
7–34 Migrating Your ULTRIX Application to a DIGITAL UNIX System