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| All-Resident C Programs |
Given
the large number of available library functions and the wide variety of functionality
they provide, it is probable that few C programs make use of all the library
support routines. Even though it is typically very difficult to determine
the minimum number of required support routines, it is usually possible to
specify some subset of the entire library. (For example, programs that do
not use coprocesses do not need the coprocess support routines.) Therefore,
an important part of the linking process must be some way for the programmer
to specify the set of support routines required by the program. This tailoring
ability is available via the
<resident.h>
header file.
Including the
<resident.h>
header file causes
the compiler to generate external symbols for various groups of support routines.
Each external symbol causes a corresponding group of support routines to
be included when the program is linked. Which external symbols are generated
and, therefore, which support routines are linked into the program, is controlled
by defining specific macro names prior to the inclusion of
<resident.h>
in the
C source file.
For example, defining the macro name
RES_VSAM
causes
<resident.h>
to generate
an external symbol for the VSAM I/O support routines when the file including
it is compiled. When the program is linked (including the object code from
the
<resident.h>
file), the linker includes these routines as part of
the program load module.
By confining the all-resident tailoring process to a
single source file, it is possible to create both an all-resident version
of the program and a transient version. The all-resident version is created
by including the
<resident.h>
object code and linking with the all-resident library.
For the transient version, neither of these steps are necessary.
Note:
An all-resident application should include
<resident.h>
in one
and only one source module. Errors may occur if
<resident.h>
is included
in several different modules of the same program. ![[cautionend]](../common/images/cautend.gif)
| Identifying the Target Operating System |
The
<resident.h>
header file generates external symbols
that are specific to CMS, OS/390, or CICS. You can define the macro name
SYS_CMS
,
SYS_OSVS
, or
SYS_CICS
to target a specific system. If you do
not define one of these macro names,
<resident.h>
tests the macro names
OSVS
and
CMS
, one of which is automatically generated by the compiler for each
of those two operating systems to determine whether or not to generate symbols
for OS/390 or CMS. If you are developing an all-resident application for
CICS, you must define the macro name
SYS_CICS
before including the
<resident.h>
header file in your program.
| Selecting the Routines to Be Included |
Macro Names Used with <resident.h> for Inclusion shows the macro names that can be defined to cause inclusion of library support routines and describes the associated support routines. By default, these routines are not included in the program load module. The Operating System column indicates whether the support routines are used under OS/390, CMS, CICS, or all three. A number appearing in the Notes column indicates that the support routines are included automatically if certain functions are used in the program. An explanation of the numbers used in the Notes column follows Macro Names Used with <resident.h> for Inclusion. (Refer to Subordinate Load Modules for more information on when support routines are included automatically.)
Note: The support routines are included automatically if
signal
or
raise
function is used, or if signal support is needed for other reasons.
costart
function is used.
remove
,
rename
,
access
, or
cmsstat
functions are used.
open
or
creat
function is used.
tmpfile
function is used.
RES_VSAM
is defined. Support routines
for any access (text, binary, or keyed) to VSAM files will be included. If
RES_VSAM
is not defined, defining
RES_VSAM_STDIO
will include
support for text or binary access to VSAM files, and defining
RES_KEYED_IO
will include support for keyed access.
NO_OE_SOCKETS
and
ONLY_OE_SOCKETS
can be used in OS/390 to control which kinds of sockets are supported.
posix
option.
fdopen
function is used
or you compile with the
posix
option.
execinit
function is used.
Note that the additional symbols
RES_SUBCOM_TSO
and
RES_SUBCOM_OE
can be used to include only TSO support or only USS support.
| Selecting the Routines to Be Excluded |
In
addition to specifying which support routines should be included,
<resident.h>
respects a number of macro names that indicate that certain support
routines should be omitted. By default, these routines are included in the
program load module, except for the subcom and socket routines. For an all-resident
program that has specified _nio to be not equal
to zero, the macro name NO_IO must be defined
prior to including the <resident.h> header
file in the program. Macro Names Used with <resident.h> for Exclusion shows these names and the associated support
routines.
| Using Dynamic Loading |
<resident.h>
allows the programmer to decide whether dynamic loading
will be available to the program. There are three possible choices as follows:
loadm
and
loadd
functions, but the library is prohibited from
using them.
If either the
loadm
or
loadd
function is used in the program, then the necessary support routines are linked
with the load module automatically. Also, the macro name
ALLOW_LOADM
can be defined to indicate that the dynamic loading support routines
are to be linked into the load module.
ALLOW_TRANSIENT
.
| Using <resident.h> |
Sample Use of <resident.h> is an example of using
<resident.h>
. In this particular
use, signal-handling and UNIX style I/O support routines are linked with the
program. Note that the header file and macro name definitions can be added
to another program source file or confined to a source file by themselves.
Sample Use of <resident.h>
#define RES_SIGNAL /* Include signal handling support. */ #define RES_IOUTIL /* Include access, rename, remove support. */ #define RES_UNIXIO /* Include UNIX style I/O support. */ #define RES_TMPFILE /* Include temporary file I/O support. */ #if defined CMS #define RES_LIBIO /* If CMS, include support routines for */ #endif /* I/O to MACLIB/TXTLIB members. */ #if defined OSVS #define MVSXA_ONLY /* If OS, exclude MVS/370 ABEND handling. */ #endif #define ALLOW_LOADM /* Allow this program to load other load */ /* modules, but no library modules can be */ /* loaded. */ #include <resident.h>
Note:
The
dollars
compiler option must be used when compiling a C++ source file that
contains
<resident.h>
.
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Copyright © 2001 by SAS Institute Inc., Cary, NC, USA. All rights reserved.