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[Michael "Ford" Ditto]

In article <10628 at stb.UUCP> michael at stb.UUCP (Michael) writes:
>In article <1375 at umbc3.UMD.EDU> alex at umbc3.UMD.EDU (Alex S. Crain) writes:
>>restructuring, etc. gcc is particlarly obnoxious with regard to setjmp() /
>>longjmp(), because of the way variables are placed in registers (which
>>are *not* saved/restored by setjmp()/longjmp().
>
>W h a t ? Setjmp/longjmp take a jmpbuf as an argument; in every 68000 system
>I've seen, this is an array big enough to store a movem d0-d7/a0-a6 (13
>longs).

You're correct.

Despite his asterisk-emphasized "*not*", I think Alex knew what he
was saying but just got the polarity of his sentence backward :-).
setjmp/longjmp *do* save/restore registers, and that is, indirectly,
what makes some programs break.

Some code assumes that all variables which are *not* declared as
"register" will *not* be saved/restored by setjmp/longjmp.  This
is true with simple-minded compilers, but it is not true of gcc,
and ANSI C specifies that *no* assumptions may be made about this
behavior.  In fact, I think it says that values of any automatic
variables are undefined after setjmp() returns via longjmp().
-- 
					-=] Ford [=-

"The number of Unix installations	(In Real Life:  Mike Ditto)
has grown to 10, with more expected."	ford at kenobi.cts.com
- The Unix Programmer's Manual,		...!sdcsvax!crash!elgar!ford
  2nd Edition, June, 1972.		ditto at cbmvax.commodore.com