C/C++ Programmer's Guide (G06.27+, H06.03+)

Mixed-Language Programming for TNS Programs
HP C/C++ Programmer’s Guide for NonStop Systems—429301-010
7-26
Variables and Parameters
•
The @ operator for a small-memory-model parameter
•
The $XADR standard function for a large-memory-model parameter
In this example, a TNS C large-memory-model module contains TNS C routine
C_PARAM_FUNC, which is to be passed as a parameter. The TAL module contains:
•
An EXTERNAL procedure declaration for C_PARAM_FUNC
•
TAL_PROC, which expects C_PARAM_FUNC as a parameter
•
TAL_CALLER, which calls TAL_PROC and passes C_PARAM_FUNC as a
parameter
TAL Module
INT i;
STRING .EXT s[0:9];
PROC c_param_func (i, s) !EXTERNAL procedure declaration
LANGUAGE C; ! for C routine expected as
INT i; ! a parameter
STRING .EXT s; !Extended indirection for large-
EXTERNAL; ! memory-model
PROC tal_proc (x); !TAL routine that expects
PROC(32) x; ! a large-memory-model C routine
BEGIN ! as a parameter
CALL x (i, $XADR (s));
END;
PROC tal_caller;
BEGIN
CALL tal_proc (c_param_func);
END;
PROC m main;
BEGIN
CALL tal_caller;
END;
C Module
void C_PARAM_FUNC (short i, char * s)
{ /* C routine to be passed as */
/* a parameter to TAL_PROC */
}
When you pass a large-memory-model TNS C routine as a parameter, the compiler
passes a 32-bit address that contains PEP and map information in the high-order word
and a zero in the low-order word. When you pass a small-memory-model TNS C
routine as a parameter, the compiler passes a 16-bit address that contains PEP and
map information.