From:	SMTP%"cowan@btgmax.zko.dec.com" 18-MAR-1994 11:52:14.90
To:	EVERHART
CC:	
Subj:	example using lib$vm_malloc

From: cowan@btgmax.zko.dec.com (Ken Cowan)
X-Newsgroups: comp.os.vms
Subject: example using lib$vm_malloc
Date: 17 Mar 1994 14:16:54 GMT
Organization: Digital Equipment Corporation
Lines: 87
Distribution: world
Message-ID: <2m9oom$2a9@jac.zko.dec.com>
Reply-To: cowan@btgmax.zko.dec.com (Ken Cowan)
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To: Info-VAX@CRVAX.SRI.COM
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I recieved a request to post the calling sequences for lib$vm_malloc
and friends.  

With the exception of setting errno, lib$vm_malloc, lib$vm_calloc
and lib$vm_realloc have the exact same calling sequence as
the stnadard C library.  

lib$vm_free is somewhat different.  Some old implementations of
free() returned a status code.  ANSI C defines free() as a void
function.  If you use the ANSI C definition, then ignore the return
value from lib$vm_free.  If you need a return value, be aware
that lib$vm_free returns a VMS condition code.  So, your
private malloc package might look like the code below.  Note that
if you do not have the CMA TIS support (in an image SYS$LIBRARY:CMA$TIS_SHR),
then change:
	cma$tis_errno_set_value( ENOMEM);
to
	errno = ENOMEM;
and
	cma$tis_vmserrno_set_value( status );
to
	vaxc$errno = status;

[In case you are curious, the CMA TIS support is to implement
thread local copies of errno.  These calls work fine for 
single-threaded programs too]

KC


void *my_calloc(size_t nmemb, size_t size)
{
    void *ptr;
    ptr = LIB$VM_CALLOC(nmemb,size);
    if (ptr == NULL) {
	cma$tis_errno_set_value( ENOMEM );
	return NULL;
    }
    return ptr;
}

void *my_malloc(size_t size)
{
    void *ptr;
    ptr = LIB$VM_MALLOC(size);
    if (ptr == NULL) {
	cma$tis_errno_set_value( ENOMEM );
	return NULL;
    }
    return ptr;
}

void *my_realloc(void *oldptr, size_t size)
{
    void *ptr;
    ptr = LIB$VM_REALLOC(oldptr, size);
    if (ptr == NULL) {
	cma$tis_errno_set_value( ENOMEM );
	return NULL;
    }
    return ptr;
}

int my_free(void *ptr)
{
    int status;
    if ((status = LIB$VM_FREE(ptr)) & 1) {
	return 0;
    } else {
	cma$tis_errno_set_value( EVMSERR );
	cma$tis_vmserrno_set_value( status );
	return -1;
    }
}

int my_cfree(void *ptr)
{
    return my_free( ptr );
}

-- 
Ken Cowan, ZK2-3/Q8				cowan@rtl.enet.dec.com
Digital Equipment Corporation			decwrl!rtl!cowan
110 Spit Brook Rd,
Nashua, NH 03062