Intel XENIX 286 Programmers Guide (86) - Tenox.tc

XENIX Programming cc: C Compiler
Creating Smaller and Faster Programs
You can create smaller and faster C programs by using the optimizing options available
with the cc command. These options reduce the size of a compiled program by
removing unnecessary or redundant instructions or unnecessary sym bol information.
Smaller programs usually run faster and save valuable space.
Creati ng Opti mized Object Files
You can create an optimized object file or an optimized program from a given source
file by using the -0 (for "optimize") option. This option reduces the size of the object
file or program by removing unnecessary instructions. For example, the command
cc -0 main.c
creates an optimized program from the source file main.c. The resulting object file or
program is smaller (in bytes) than if the source had been compiled without the option. A
smaller object file usually means faster execution.
The -0 option applies to source files only; existing object files are not optimized if
included with this option. The option must appear before the names of the files you
wish to optimize. For example, the command
cc -0 add.c main.c
optimizes add.c and main.c. You have different levels of optimization available, The
default is to favor code size and execution time. See the cc man page in Appendix 8
for more information about levels of optimization.
You can combine the -0 and -c options to compile and optimize source files without
linking the resulting object files. For example, the command
cc -0 -c main.c add.c
creates separate optimized object files from the source files main.c and add.c.
Although optimization is very useful for large programs, it takes more time than regular
compilation. In general, it should be used in the last stage of program development,
after the program has been debugged.
Stripping the Symbol Table
You can reduce the size of a program's executable file by using the -s option. This
option directs cc to remove items from the sy mbol table. The symbol table contains
information about code relocation and program symbols and is used by the XENIX
debugger adb to allow symbolic references to variables and functions when debugging.
The information in this table is not required for execution and may be removed when the
program has been completely debugged.
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