_xalloc()
 Allocate memory and return NULL if unsuccessful
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 C Prototype

     #include "Extend.h"
     void far *_xalloc(unsigned int size)

 Arguments

     size is the number of bytes to allocate.

 Returns

     _xalloc() returns a far pointer to the allocated memory or NULL if the
     requested memory could not be allocated.

 Description

     _xalloc() allows a C or Assembly language function to allocate memory
     from Clipper's fixed heap.  If the allocation request is unsuccessful,
     a NULL pointer is returned.

     Memory allocated with _xalloc() must be freed after use with _xfree().

 Examples

     From C:

     char *mem;
     mem = _xalloc(32);

     From Assembly language:

     EXTRN   __xalloc:FAR
       mov   ax, 32
       push  ax
       call  __xalloc    ; pointer in DX:AX
       add   sp, 2       ; reset stack pointer

 Files:  Library is CLIPPER.LIB, header file is Extend.h.