Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (H-K)
Guardian Procedure Calls Reference Manual—522629-013
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HIST_GETPRIOR_ Procedure
The workspace structure has an invalid version identifier. This error can occur
if HIST_GETPRIOR_ is called without first calling the HIST_INIT_ procedure or
if the workspace structure has become corrupted.
workspace input, output
INT .EXT:ref:(HISTWORKSPACE_TEMPLATE)
identifies the context and format of the process state to be displayed by the next
HIST_FORMAT_ procedure call. On input, it must have already been initialized by
a previous call to the HIST_INIT_ procedure and might have been modified by
previous calls to HIST_GETPRIOR_. On output, it identifies the previous
unsuppressed context. See “Considerations.”
Considerations
•
Suppression of a stack frame by HIST_INIT_ or HIST_PRIOR_ is determined by a
bit mask in the field
workspace.FrameSuppress. The HIST_INIT_ procedure
initializes the field to a default set of transition frames, or to zero (0) if the
HO_NoSuppress option is specified in the call to HIST_INIT_.
•
The procedure activations or stack frames to be displayed must exist and remain
undisturbed on the stack. You must therefore use care to ensure that these
procedure activations are not disturbed while the stack trace is taking place. For
example, if a stack trace is initiated from the context of the caller or by using a
jump buffer, the procedure that called HIST_INIT_ or the
setjmp() function
should not exit before the calls to HIST_GETPRIOR_.
•
You can call HIST_GETPRIOR_ without calling HIST_FORMAT_ to skip a frame in
a stack trace. For example, a procedure can generate a stack trace starting from
its caller (instead of itself) by calling HIST_INIT_ with the HO_Init_Here option, and
then calling HIST_GETPRIOR_ before the first call to HIST_FORMAT_.
Example
error := HIST_GETPRIOR_ ( hws );