Debug flags, setdflags and wscheck

[AndyS|Dyalog]

The Dyalog APL User Guide lists a number of debug flags which can be used when trying to identify issues which cause Dyalog APL to terminate abnormally. They specify when a workspace integrity check (wscheck) is to be run. These workspace integrity checks check the consistancy of the workspace, and if a problem is found, APL terminates having generated an APL core file.

A wscheck is always performed immediately after a workspace has been loaded, and also as the first task during a workspace save.

It is also possible to enable and disable these wschecks under program control.

To force a single wsheck:

      2 ⎕nq '.' 'wscheck'

To change the current debug level:

      previous_value←2 ⎕nq '.' 'setdflags' newvalue

The most common values, their equivalent startup flags and their purpose are:

      Value   Startup flag   Purpose
        0        <none>      no extra wscheck
        2        -Dc         wscheck after each callback
       64        -DW         wscheck after each line of APL
      128        -Dw         wsheck on return to session input

Note that the values are additive - which is why they are all powers of 2!
Note also that other values are valid but should be used only when directed to by Dyalog support; in particular 32 causes the contents of the workspace to be shuffled around - this will have a huge impact on the speed of execution of the code in your workspace !