Strange warning (variable might be clobbered by `longjmp' or

[Jeffrey A Law]

  In message < 199709022224.PAA12532@cygnus.com >you write:
  > of setjmp/longjmp.  Unfortunately, this is done in a somewhat confusing way.
  > It appears that the sequences for setjmp/longjmp are setting a pseudo to
  > 0/1, and then branching to the same place which then branches off to the
  > handler if this pseudo is 1.  This just confuses the control flow.  I have
  > no idea why it is doing this, or whether my understanding is correct.
That is how setjmp/longjmp generally work.

When one calls setjmp it saves the state into a jmp_buf and returns zero.

When you longjmp control returns to the site of the setjmp; and the register
state is set up such that it appears that the setjmp call returned a second
time with a return value of one.

I don't know if it's relavent, but gcc knows that certain functions return
twice (setjmp, sigsetjmp, savectx, qsetjmp, etc etc).   By emitting rtl
itself to perform the actions of setjmp/longjmp we may be defeating the
purpose of the code to determine that some calls may return twice.


Jeff