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Re: Safety of casting from 'long' to 'int'

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: Safety of casting from 'long' to 'int'
Date	2026-05-12 22:31 -0700
Organization	A noiseless patient Spider
Message-ID	<86lddnlvtr.fsf@linuxsc.com> (permalink)
References	<10su8cn$am9i$1@dont-email.me> <10tdu47$pms4$3@kst.eternal-september.org> <10tgqgk$rpk$1@reader1.panix.com> <10thb36$1prnt$1@kst.eternal-september.org> <10tlc73$qq2$1@reader1.panix.com>

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cross@spitfire.i.gajendra.net (Dan Cross) writes:

[...]

> It is not clear to me that `longjmp` out of a non-nested signal
> handler is still well-defined as of C11, though it is explicitly
> stated to be C89.

It seems you are misunderstanding what the standards are saying.
The description of longjmp() says (paraphrasing) that it restores
the environment where the relevant setjmp() was done.  There is
in C89 a passage about returning from signal handlers and so
forth, but that is followed by a carveout for nested signal
handlers, which in C89 is undefined behavior.  (I assume that
also holds for C90 but I haven't verified that.)

Starting in C99, any mention of interrupts and signal handlers was
removed, along with the carveout.  Because there is a definition
for what longjmp() does, the behavior is defined, and there is no
undefined behavior (not counting things like doing a longjmp()
with a jmp_buf that wasn't set up, etc).  Removing the mention of
interrupts and signals, and also removing the carveout, only makes
longjmp() more defined, not less.

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Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 10:16 +0200
  Re: Safety of casting from 'long' to 'int' Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-05 11:11 +0200
    Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 11:25 +0200
      Re: Safety of casting from 'long' to 'int' Richard Harnden <richard.nospam@gmail.invalid> - 2026-05-05 11:12 +0100
        Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 14:12 +0200
        Re: Safety of casting from 'long' to 'int' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-05-05 16:43 -0400
      Re: Safety of casting from 'long' to 'int' Bart <bc@freeuk.com> - 2026-05-05 11:41 +0100
        Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 14:31 +0200
          Re: Safety of casting from 'long' to 'int' Bart <bc@freeuk.com> - 2026-05-05 14:26 +0100
            Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 16:36 +0200
              Re: Safety of casting from 'long' to 'int' Bart <bc@freeuk.com> - 2026-05-05 17:21 +0100
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 19:19 +0200
              Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-05 15:25 -0700
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 09:03 +0200
              Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-05 16:00 -0700
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 09:20 +0200
            Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-05 15:21 -0700
              Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 12:20 +0200
                Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-06 03:36 -0700
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 12:49 +0200
              Re: Safety of casting from 'long' to 'int' Bart <bc@freeuk.com> - 2026-05-06 12:00 +0100
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 14:34 +0200
                Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-06 12:23 -0700
                [meta] Optimizing posting and communication (was: something about UB) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-05-06 22:15 +0200
                Re: [meta] Optimizing posting and communication (was: something about UB) cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-06 22:42 +0000
                Re: [meta] Optimizing posting and communication Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-06 17:01 -0700
              Re: Safety of casting from 'long' to 'int' Bart <bc@freeuk.com> - 2026-05-06 12:32 +0100
                Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-06 14:52 +0200
  Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-05 13:27 +0000
    Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-05 16:45 +0200
    Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-05 16:22 -0700
      Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-07 01:39 +0000
        Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-06 21:41 -0700
          Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-08 18:26 +0000
            Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-08 15:41 -0700
        Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-06 23:22 -0700
          Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-08 19:06 +0000
            Re: Safety of casting from 'long' to 'int' "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-08 13:22 -0700
              Re: Safety of casting from 'long' to 'int' "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-05-08 13:27 -0700
            Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-12 22:31 -0700
              Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-13 15:47 +0000
                Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-13 11:59 -0700
                Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-13 20:45 +0000
                Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-13 15:28 -0700
                Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-13 15:33 -0700
                Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-13 23:56 +0000
        Re: Safety of casting from 'long' to 'int' David Brown <david.brown@hesbynett.no> - 2026-05-07 10:33 +0200
        Re: Safety of casting from 'long' to 'int' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-05-07 18:08 -0400
          Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-08 16:13 +0000
            Re: Safety of casting from 'long' to 'int' scott@slp53.sl.home (Scott Lurndal) - 2026-05-08 16:42 +0000
              Re: Safety of casting from 'long' to 'int' Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-05-08 16:57 +0000
                Re: Safety of casting from 'long' to 'int' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-05-08 17:51 -0400
                Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-08 23:03 +0000
            Re: Safety of casting from 'long' to 'int' scott@slp53.sl.home (Scott Lurndal) - 2026-05-08 17:01 +0000
            Re: Safety of casting from 'long' to 'int' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-05-09 08:37 -0700
              Re: Safety of casting from 'long' to 'int' cross@spitfire.i.gajendra.net (Dan Cross) - 2026-05-09 22:15 +0000
                Re: Safety of casting from 'long' to 'int' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-05-09 16:24 -0700

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