The use of shared variables requires careful attention to ensure
that correct values are communicated among relevant processes. For
example, if one process writes a shared variable in the same
simulation cycle that another process reads the variable, the VHDL
standard does not define what value is read. Similarly, if two or
more processes write to the same shared variable in the same
simulation cycle, the standard does not define what value should be
written to the variable.
Care must be taken if overloaded functions are differentiated solely
by the type of their return values. The previous version of the VHDL
standard, 1076-1987, did not require that differentiations on output
types be supported. The current standard, 1076-1993, however, has
included the requirement that differentiations based solely on output
type be supported.
