This call creates a code segment alias descriptor for a data segment passed as input.
DosCreateCSAlias
DataSelector (SEL) - input
A selector returned by a call to DosAllocSeg with no sharing options specified can be used as the data segment specified with DosCreateCSAlias. However, to be CS alias, the segment must be a privilege level 2 or privilege level 3 non-shared segment.
A CS alias segment must be exclusively accessible by the process and cannot be a huge segment. Selectors of shared memory segments and dynamically linked global data segments cannot be used as input for DosCreateCSAlias.
The code segment selector returned by DosCreateCSAlias is valid for CS. If a procedure is stored in the data segment, it can be called using the CS alias. The procedure may be called from privilege level 3 or I/O privilege level.
Use DosFreeSeg to free a CS alias selector created with DosCreateCSAlias. Procedures in the segment can continue to be referenced if the data selector for the aliased segment is passed to DosFreeSeg, because the CS alias selector is not affected. Once both selectors have been passed to DosFreeSeg, the segment is deallocated.
Family API Considerations
The returned selector is the segment address of the allocated memory. When the returned selector or the original selector is freed, OS/2 immediately deallocates the block of memory.