CRE Programmer's Guide

CRE Services
Common Run-Time Environment (CRE) Programmer’s Guide—528146-004
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Native CRE Memory
Accessing Heap Data:
•
C and TAL routines can reference data allocated on the heap by storing the
address of the data into a pointer and referencing the pointer in an expression.
Routines written in COBOL and FORTRAN must call C or TAL routines to
reference heap data.
•
A TAL routine can call a C routine to allocate or free heap space. The following
code fragment shows a TAL routine, Do_It, that calls a C routine, GETSPACE, to
get space from the heap. GETSPACE gets a block from the heap and stores a
value in the first 16-bit word of the block. When GETSPACE returns, its value is a
pointer to the newly allocated block. Do_It reads the value stored by GETSPACE.
The C routine is shown first:
#include <stddef.h> nolist
#include <stdlib.h> nolist
int *GETSPACE( int nbytes )
{ int *p;
p = (int *) malloc( nbytes )
if (p != NULL) *p = 100;
return p;
}
The following TAL code calls the C routine GETSPACE:
INT(32) PROC TAL_Malloc = "GETSPACE" ( nbytes ) LANGUAGE C;
INT nbytes;
EXTERNAL;
PROC Do_It;
BEGIN
INT .EXT T_Ptr;
@T_Ptr := TAL_Malloc( 1000 );
IF (@T_Ptr = OD) OR (T_Ptr <> 100) THEN
BEGIN
! Handle error...
END;
END;
Heap Statistics:
•
The TNS CRE maintains statistics that describe heap utilization.
•
The native CRE does not support statistics that describe heap utilization.
Native CRE Memory
In the native CRE, the data spaces that your program can use to share data are:
•
The user heap
•
Global data
The native CRE allocates memory using the same layout in the OSS and Guardian
environments. For a given total amount of memory allocated to a process, however,