The ANSI standard specifies exactly which names (for example,
variable names, function names, type definition names) are reserved.
The intention is to make it easier to port programs from one implementation
to another without unexpected collisions in names. For example,
since the ANSI C standard does not reserve the identifier open,
an ANSI C program may define and use a function named open
without colliding with the open(2) system
call in different operating systems.
HP Header File and Library Implementation of Name
Spaces |
 |
The HP header files and libraries have been designed to support
several different name spaces. On HP-UX systems, four name spaces
are available:
The HP library implementation has been designed with the assumption
that many existing programs will use more routines than those allowed
by the ANSI C standard.
If a program calls, but does not define, a routine that is
not in the ANSI C name space (for example, open),
then the library will resolve that reference. This allows a clean
name space and backward compatibility.
The HP header file implementation uses preprocessor conditional
compilation directives to select the name space. In non-ANSI mode,
the default is the HP-UX name space. Compatibility mode means that
virtually all programs that compiled and executed under previous
releases of HP C on HP-UX continue to work as expected. The following
table provides information on how to select a name space from a
command line or from within a program using the defined libraries.
Table 5-2 Selecting
a Name Space in ANSI Mode
When using the name space... | Use command line option... | or #define in source program | Platform |
|---|
HP-UX | -D_HPUX_SOURCE | #define _HPUX_SOURCE | HP-UX Only |
XOPEN | -D_XOPEN_SOURCE | #define _XOPEN_SOURCE | HP-UX Only |
POSIX | -D_POSIX_SOURCE | #define _POSIX_SOURCE | HP-UX |
ANSI C | default | default | HP-UX |
In ANSI mode, the default is ANSI C name space. The macro
names _POSIX_SOURCE,
_XOPEN_SOURCE,
and _HPUX_SOURCE
may be used to select other name spaces. The name space may need
to be relaxed to make existing programs compile in ANSI mode. This
can be accomplished by defining the _HPUX_SOURCE
macro definition.
For example, in HP-UX:
#include <sys/types.h>
#include <sys/socket.h> |
results in the following compile-time error in ANSI mode because
socket.h uses
the symbol u_short
and u_short is
only defined in the HP-UX name space section of types.h:
"/usr/include/sys/socket.h", line 79: syntax error:
u_short sa_family; |
This error can be fixed by adding -D_HPUX_SOURCE
to the command line of the compile.
