PGI Fortran Reference manual - The Portland Group

Fortran StatementsDescriptionBeing volatile indicates to the compiler that, at any time, the variable might change or beexamined from outside the Fortran program. The impact on the programmer is that anytimea volatile variable is referenced, the value must be loaded from memory. Furthermore, anyassignment to the volatile variable must be written to memory.If nitem names a common block, all members of the block are volatile. The volatile attribute of avariable is inherited by any direct or indirect equivalences, as shown in the example.Volatile Attribute ExampleThe following example declares both the integer variable xyz and the real variable abc to bevolatile.integer, volatile :: xyzreal :: abcvolatile :: abcVolatile Statement ExampleCOMMON /COM/ C1, C2VOLATILE /COM/, DIR ! /COM/ and DIR are volatileEQUIVALENCE (DIR, X) ! X is volatileEQUIVALENCE (X, Y ) ! Y is volatile3.23. WAITPerforms a wait operation for specified pending asynchronous data transfer operations.F2003SyntaxWAIT (wait_specs_list)wait_specs_list can include any of the following specifiers:UNIT = ] file-unit-numberA file-unit-number must be specified. If the optional characters UNIT= are omitted, the fileunit-numberis the first item in the wait-spec-list.END = labellabel must be the statement label of a branch target statement that appears in the samescoping unit as the WAIT statement.END= specifier has no effect if the pending data transfer operation is not a READ.PGI Fortran Reference Guide 62