NAME
stdsyms — description of HP-UX header file organization
DESCRIPTION
HP-UX header files are organized in a manner
that allows for only a subset of the symbols
available in that header file to be visible to an application
that conforms to a specific standard.
The ANSI-C, POSIX.1, POSIX.2, and XPG4
standards each reserve a certain set of symbols
for that standard's namespace.
In addition, the HP-UX implementation of XPG3 and the "OSF AES/OS"
provides for a clean namespace although this is not a specific
requirement of those standards.
The following rules apply in determining
what symbols are reserved for any standard.
These symbols are reserved for the standard
and for use by the implementation,
and must be either avoided altogether,
or used exactly as defined by the specified standard.
All symbols defined by the desired standard are reserved.
Refer to the appropriate standards documentation
for a complete list of reserved symbols.
All symbols beginning with an underscore
followed by another underscore or an uppercase letter
are reserved for the implementation.
All external identifiers beginning with an underscore
are reserved for the implementation.
The following is a list of feature test macros
which must be defined
to obtain the appropriate namespace from the header files.
- __STDC__
This symbol is automatically defined by the
ANSI-C pre-processor
(/opt/langtools/lib/cpp.ansi)
and is automatically defined when specifying an
ANSI-C compile
(cc -Aa).
Using the strict ANSI option
-Aa
requests a pure ANSI-C namespace, which is the smallest subset of the
HP-UX namespace available.
The
-Aa
option also enables the inclusion of ANSI-C-style function prototypes for increased type checking.
Note that the default namespace when using the
-Aa
option is the ANSI-C namespace; therefore a broader namespace must be
requested
if it is desired.
- _POSIX_SOURCE
As documented in the IEEE POSIX.1 standard, the programmer is required
to define the
_POSIX_SOURCE
feature test macro to obtain the POSIX.1 namespace and POSIX.1
functionality.
This feature test macro can be defined,
either by using compiler options
(-D_POSIX_SOURCE)
or by using
#define
directives in the source files before any
#include
directives.
Note that the default POSIX namespace is the POSIX.1-1990
namespace.
It is necessary to define the
_POSIX1_1988
feature test macro in addition to the
_POSIX_SOURCE
macro in order to obtain the POSIX.1-1988 namespace.
- _POSIX_C_SOURCE
As documented in the IEEE POSIX.2
standard, the programmer is required to define the
_POSIX_C_SOURCE
feature test macro with a value of 2 to obtain the POSIX.1
and POSIX.2 namespaces and functionality.
This feature test macro can be defined,
either by using compiler options
(-D_POSIX_C_SOURCE=2)
or by using
#define
directives in the source files before any
#include
directives.
This macro is also automatically defined in the XPG4
X/Open namespace (that is, whenever
_XOPEN_SOURCE
and
_XPG4
are defined without defining
_XPG2
or
_XPG3).
- _XOPEN_SOURCE
As documented in the XPG3 and XPG4
standards, the programmer is required to define the
_XOPEN_SOURCE
feature test macro to obtain X/Open functionality.
This feature test macro can be defined,
either by using compiler options
(-D_XOPEN_SOURCE)
or by using
#define
directives in the source files before any
#include
directives.
Although XPG3 does not specify any namespace pollution rules, XPG4
has instituted such rules.
Therefore, the HP-UX operating system provides clean namespaces whenever
_XOPEN_SOURCE
is defined.
The current default X/Open namespace is that corresponding to
XPG3. To request other versions of the X/Open namespace, define
_XPG2
or
_XPG4
in conjunction with
_XOPEN_SOURCE.
- _AES_SOURCE
As documented in the "OSF AES/OS"
standard, the programmer is required to define the
_AES_SOURCE
feature test macro to obtain OSF functionality.
This feature test macro can be defined,
either by using compiler options
(-D_AES_SOURCE)
or by using
#define
directives in the source files before any
#include
directives.
Although the AES does not specify any namespace pollution rules,
the other standards have instituted such rules. Therefore HP-UX
provideds a clean namespace whenever
_AES_SOURCE
is defined.
- _HPUX_SOURCE
The programmer can define the
_HPUX_SOURCE
feature test macro to obtain the HP-UX namespace and complete HP-UX
functionality.
Note that the HP-UX namespace is currently a superset
of all of the above mentioned namespaces.
When using the compatibility-mode compiler
(cc(1)
without the
-Aa
option), the HP-UX namespace is provided by default.
The programmer must request one of the other namespaces
as described above to obtain the appropriate subset of the HP-UX
namespace.
When using the strict ANSI-C-mode compiler
(cc -Aa),
the programmer must specifically request a broader namespace.
The
_HPUX_SOURCE
feature test macro can be defined,
either by using compiler options
(-D_HPUX_SOURCE)
or by using
#define
directives in the source files before any
#include
directives.
The following is a list of miscellaneous feature test macros
that provide various additional features.
- __cplusplus
This symbol is automatically defined by the HP C++ compiler. Defining this
macro enables the C++ function prototypes in system header files.
The default namespace for HP C++ is the ANSI-C namespace. To obtain another
namespace define the appropriate feature test macro.
HP C++ uses the ANSI-C preprocessor by default. To get the compatibility mode
preprocessor, use the
-Ac
option to
cc(1).
The compatibility mode preprocessor uses the HP-UX namespace
(_HPUX_SOURCE).
- _POSIX1_1988
This feature test macro should be defined
when the
POSIX.1-1988
namespace is required.
It should be used in conjunction with the
_POSIX_SOURCE
macro if the default
POSIX.1-1990
namespace is not desired.
This macro is defined automatically whenever
_AES_SOURCE
or
_XPG3
is requested.
- _XPG2
The
_XPG2
macro can be defined when using the compatibility-mode compiler
to obtain XPG2 functionality. This provides XPG2 specified
function declarations and macros in the HP-UX namespace.
Note that the values obtained from most of the macros
available when using this option are now available
at run-time via the
pathconf(),
fpathconf(),
and
sysconf()
system calls (see
pathconf(2)
and
sysconf(2)).
Use of the
_XPG2
macro is strongly discouraged because
it gives access to obsolete functionality.
Note that no function prototypes are provided
when using this feature test macro.
- _XPG3
The
_XPG3
feature test macro is defined automatically
if the programmer has requested the XPG3
namespace (i.e., defined
_XOPEN_SOURCE,
but not some other conflicting namespace such as
_XPG2
or
_XPG4).
- _XPG4
The
_XPG4
feature test macro is provided so that the programmer can obtain the
XPG4 namespace, since it differs slightly from the
_XPG3
namespace.
In order to obtain the XPG4 namespace, the programmer must
define both the
_XOPEN_SOURCE
and
_XPG4
feature test macros.
The
_XOPEN_SOURCE
and
_XPG4
feature test macros can be defined,
either by using compiler options
(-D_XOPEN_SOURCE -D_XPG4)
or by using
#define
directives in the source files before any
#include
directives.
- _SVID2
The
_SVID2
macro can be defined when using the compatibility mode compiler to obtain
SVID2 function return types in the HP-UX namespace.
The default return types of many functions have since been changed
in the HP-UX operating system to align with the ANSI-C, POSIX, X/Open,
and OSF standards.
- _CLASSIC_TYPES
The
_CLASSIC_TYPES
macro can be defined by the programmer
to obtain pre-7.0 style
function return types and structure element types.
This macro has been provided
only as a transition aid when migrating
from the pre-7.0 version of HP-UX to standards-based HP-UX.
Use of this macro is strongly discouraged
as this functionality will be removed in a future release of
HP-UX.
Note that no function prototypes are provided
when using this feature test macro.
