D

Syntax

    -Dname=definition | -Dname= | -Dname 

Purpose
Defines the identifier name as in a #define preprocessor directive. definition is an optional definition or value assigned to name.

Notes
The identifier name can also be defined in your source program using the #define preprocessor directive.

-Dname= is equivalent to #define name.

-Dname is equivalent to #define name 1. (This is the default.)

To aid in program portability and standards compliance, the AIX Version 4 OPerating System provides several header files that define macro names you can set with the -D option. You can find most of these header files either in the /usr/include directory or in the /usr/include/sys directory. See "Header Files Overview" in the AIX Version 4 Files Reference for more information.

The configuration file uses the -D option to specify the following predefined macros:

• _POWER
• _AIX
• _AIX32
• _IBMR2
• _ANSI_C_SOURCE

To ensure that the correct macros for your source file are defined, use the -D option with the appropriate macro name. If your source file includes the /usr/include/sys/stat.h header file, you must compile with the option -D_POSIX_SOURCE to pick up the correct definitions for that file.

If your source file includes the /usr/include/standards.h header file, _ANSI_C_SOURCE, _XOPEN_SOURCE, and _POSIX_SOURCE are defined if you have not defined any of them.

The -Uname option has a higher precedence than the -Dname option.

Example
To specify that all instances of the name COUNT be replaced by 100 in myprogram.c, enter:

xlC myprogram.c -DCOUNT=100

This is equivalent to having #define COUNT 100 at the beginning of the source file.

List of Compiler Options and Their Defaults
Options that Specify Preprocessor Options