extern int x1f4_look_shuffle (void *subtext, unsigned *line);
x1f4_look_shuffle function stores some byte offset in the textual
representation of the program for which the
subtext step by step
execution context was created at the address indicated by
offset may be indicative of the source position of the next instruction to be
executed, and as well as of the source position of the instruction whose
execution just failed (since instruction pointer is not advanced for execution
failures). The function is intended to help with determining where and why the
program execution failed.
The function returns
It should be deployed for step by step program execution only. For single
function call program execution consider
See Step By Step Procedural Program Execution.