/REENTRANCY

    /REENTRANCY=option
    /REENTRANCY=TOLERANT (D)

 Controls the type of reentrancy that reentrant VSI C RTL routines
 will exhibit.

 (See also the decc$set_reentrancy RTL routine.)

 This qualifier is for use only with a module containing the main
 routine.

 The reentrancy level is set at run time according to the
 /REENTRANCY qualifier specified while compiling the module
 containing the main routine.

 You can specify one of the following options:

 AST               Uses the __TESTBITSSI builtin to perform simple
                   locking around critical sections of RTL code, and
                   may additionally disable asynchronous system
                   traps (ASTs) in locked region of codes.  This
                   type of locking should be used when AST code
                   contains calls to VSI C RTL I/O routines.

 MULTITHREAD        Designed to be used in conjunction with the
                   DECthreads product.  It performs DECthreads
                   locking and never disables ASTs.

 NONE              Gives optimal performance in the RTL, but does
                   absolutely no locking around critical sections of
                   RTL code.  It should only be used in a single
                   threaded environment when there is no chance that
                   the thread of execution will be interrupted by an
                   AST that would call the VSI C RTL.

 TOLERANT          Uses the __TESTBITSSI builtin to perform simple
                   locking around critical sections of RTL code, but
                   ASTs are not disabled.  This type of locking
                   should be used when ASTs are used and must be
                   delivered immediately.  This is also the default
                   reentrancy type.