Open System Services Porting Guide (G06.24+, H06.03+)

Interoperating Between Programming Environments
Open System Services Porting Guide—520573-006
5-3
Header Files
Header Files
Header files in the Guardian and OSS environment are stored in different places, but
their contents are identical. In most cases, the names of the header files are similar: for
example, sys/types.h in OSS corresponds to SYSTYPEH in Guardian. Truncation
of some characters before the trailing H is common (as shown in the preceding
example). One anomaly is that cextdecs.h corresponds to CEXTDECS (no trailing H
for historical reasons).
Use of Feature-Test Macros
The C compiler provides feature-test macros, for example: _POSIX_SOURCE,
_POSIX_C_SOURCE, _XOPEN_SOURCE, and _TANDEM_SOURCE. Sometimes
options are also selected by macros. For example, _IGNORE_LOCALE is used in
ctype.h to select C/POSIX locale macros rather than internationalized functions. Use
of these macros determine whether a particular set of features will be included from
header files. Feature-test macros also enable you to check how well a program
compiles.
The C header files contain definitions required by the ISO/ANSI C standard, the
POSIX.1 standard, the POSIX.2 standard, and the XPG4 specifications. You control
visibility of the definitions with feature-test macros. If a program does not conform to
the POSIX-standard or XPG4 specification identifiers made visible by a feature-test
macro, the compiler issues error and warning messages. For more information about
feature-test macros, refer to the C/C++ Programmer’s Guide. See also Defined
Symbols and Header Files on page 7-12.
Table 5-1. Differences Between Guardian and OSS Environments
Guardian Environment OSS Environment
TACL command interface OSS shell for supporting command interface
PARAMs, ASSIGNs, DEFINEs for setting
process environment attributes
args, env for setting process attributes
$RECEIVE for interprocess communication Pipes for interprocess communication
Break key for switching between running
processes
Job control signals for switching between
running processes
System messages and Guardian signals
(except the kill() function)
OSS signals only
PROGID program for process identity setuid() and setgid() functions for
process identity
EDIT files ASCII text files
CRE supports shared access to standard
files
Operating system supports standard file
access