ZBasic System Library
318
ZBasic Microcontrollers
Type
Function returning UnsignedInteger
Invocation
System.Alloc(numBytes)
Parameter
Method
Type
Description
numBytes
ByVal
integral
The size of the requested allocation.
Discussion
This function allocates a block of memory from the heap of the specified size and returns the address of
the first byte of the block. If a block of the specified size cannot be allocated, zero is returned. The block
can be returned to the heap using the subroutine System.Free().
This function and the block of memory it returns must be used with great care. If your program fails to
deallocate the block using System.Free() when it is no longer needed, the heap may eventually be
exhausted. Since space for strings is also allocated from the heap, exhaustion may cause string
operations to fail. Moreover, if your program writes to memory outside of the bounds of the block, the
heap data structures may be corrupted. This may cause future heap allocation requests to fail.
For native mode devices (e.g. the ZX-24n) a heap allocation may fail if the heap size is set too small
compared to the needs of your application. To aid in determining a sufficient heap size the System
Library function System.HeapHeadRoom() may be used to discover the amount of space in the heap that
has not yet been used at the time of the call.
Example
Dim addr as UnsignedInteger
addr = System.Alloc(50)
[other code here that uses the allocated block]
Call System.Free(addr)
addr = 0
Compatibility
This function is not available in BasicX compatibility mode.
See Also
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