From: Paul Eggert <eggert@cs.ucla.edu>
To: Pip Cet <pipcet@gmail.com>, Bruno Haible <bruno@clisp.org>
Cc: 36370@debbugs.gnu.org, bug-gnulib@gnu.org
Subject: bug#36370: 27.0.50; XFIXNAT called on negative numbers
Date: Fri, 28 Jun 2019 10:46:52 -0700 [thread overview]
Message-ID: <a293f2fe-99b3-3776-f27b-35e3a93d1d34__48674.4992480212$1561746844$gmane$org@cs.ucla.edu> (raw)
In-Reply-To: <CAOqdjBfS99UpLZ-qLe4=FMXMsr+T3LUvJEsf_gfmF6wwLbqgOw@mail.gmail.com>
Pip Cet wrote:
> It's way too easy
> to do something like
>
> eassume(ptr->field >= 0 && f(ptr));
>
> when what you mean is
>
> eassume(ptr->field >= 0);
> eassume(f(ptr));
These mean the same thing. Both tell the compiler that a certain condition (A &&
B) is known to be true, and that behavior is undefined if (A && B) is false. The
fact that Gnulib+GCC implements them differently is a quality-of-implementation
issue, not a semantics issue.
> I'm saying that the programmer is
> allowed to assume that the expression passed to assume either has been
> evaluated, or hasn't been, with no in-between interpretations allowed
> to the compiler.
I don't see why that assumption is valid. It's OK if GCC partially evaluates the
expression. As a silly example, eassume (0 * dump_core () + getchar ()) is not
required to call dump_core, even if the compiler generates a call to getchar.
Perhaps we should change the comments in verify.h to make this point clearer.
next prev parent reply other threads:[~2019-06-28 17:46 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 5:36 bug#36370: 27.0.50; XFIXNAT called on negative numbers Pip Cet
2019-06-27 1:10 ` Paul Eggert
2019-06-27 6:16 ` Pip Cet
2019-06-27 8:28 ` Paul Eggert
2019-06-27 13:17 ` Pip Cet
2019-06-27 13:37 ` Eli Zaretskii
2019-06-27 19:38 ` Paul Eggert
2019-06-27 19:56 ` Pip Cet
2019-06-27 21:13 ` Paul Eggert
[not found] ` <5284eb58-3560-da42-d1d1-3bdb930eae49@cs.ucla.edu>
2019-06-27 21:37 ` Pip Cet
2019-06-27 23:45 ` Bruno Haible
[not found] ` <2715311.ceefYqj39C@omega>
2019-06-28 0:04 ` Paul Eggert
2019-06-28 11:06 ` Pip Cet
2019-06-28 12:14 ` Bruno Haible
[not found] ` <8979488.cRkkfcT1mV@omega>
2019-06-28 12:29 ` Bruno Haible
2019-06-28 13:51 ` Pip Cet
[not found] ` <CAOqdjBfS99UpLZ-qLe4=FMXMsr+T3LUvJEsf_gfmF6wwLbqgOw@mail.gmail.com>
2019-06-28 17:46 ` Paul Eggert [this message]
2019-06-28 19:11 ` Bruno Haible
[not found] ` <a293f2fe-99b3-3776-f27b-35e3a93d1d34@cs.ucla.edu>
2019-06-28 19:15 ` Pip Cet
2019-06-28 19:56 ` Bruno Haible
2019-06-28 21:08 ` Pip Cet
2019-06-29 5:41 ` Paul Eggert
[not found] ` <87168b28-192b-6666-e9b6-9cdc2ed3917a@cs.ucla.edu>
2019-06-29 6:48 ` Pip Cet
[not found] ` <CAOqdjBfcNbXFw3Fb0wgRR10PNbkJQ+88ObE9KEghLSb-ptdrbA@mail.gmail.com>
2019-06-29 17:31 ` Paul Eggert
[not found] ` <791ae316-3a6f-605a-0da5-874fe3d224c5@cs.ucla.edu>
2019-06-30 9:21 ` Pip Cet
[not found] ` <11002295.LrvMqknVDZ@omega>
2019-06-28 21:07 ` Pip Cet
2019-06-28 23:30 ` Bruno Haible
[not found] ` <2067160.1HRgjLhtDS@omega>
2019-06-29 5:40 ` Paul Eggert
2019-06-29 5:44 ` Pip Cet
[not found] ` <CAOqdjBcNA4mDiwsd_jbeePGMdUwPvkFCNdgtZvmiQnYmJNR3pA@mail.gmail.com>
2019-06-29 10:31 ` Bruno Haible
[not found] ` <2515002.Q0mBYvUW8C@omega>
2019-06-29 17:11 ` Paul Eggert
[not found] ` <99bacb9f-1192-1315-85d7-5ab4924dfef8@cs.ucla.edu>
2019-06-29 17:48 ` Bruno Haible
2019-06-30 15:30 ` Pip Cet
[not found] ` <CAOqdjBeiMno7nGKwk7SSZQob+CTyG39KRTM9EEebq7NQavLR-Q@mail.gmail.com>
2019-06-30 15:45 ` Bruno Haible
2019-07-02 23:39 ` Paul Eggert
2019-07-01 1:46 ` Richard Stallman
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