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From: "macro at orcam dot me.uk" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/107405] [13 Regression] enum change causing Linux kernel to fail to build due to Linux depending on old behavior
Date: Tue, 22 Nov 2022 14:53:01 +0000	[thread overview]
Message-ID: <bug-107405-4-xbaeGFV6dD@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-107405-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107405

--- Comment #18 from Maciej W. Rozycki <macro at orcam dot me.uk> ---
Well, according to the assertion triggered `typeof (EM_MAX_SLOTS)' will
yield a data type of a different width depending on the compiler version.
Even if this GNU extension does not constitute a part of the ABI it does
guarantee link incompatibility for a feature we've had for decades now,
even if the old semantics was unintentional.  Data corruption cannot be
ruled out.  Besides, `sizeof (EM_MAX_SLOTS)' can also be used to build a
data type (an array type) and process it.

So I think a pedantic warning is not enough to fulfil the principle of
least surprise for the real world out there.  Therefore I maintain that
for pre-C2x compilations we either need to keep the old semantics,
possibly with a fat warning under `-Wall', or as I say make it a hard
error.

  parent reply	other threads:[~2022-11-22 14:53 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-26  4:26 [Bug c/107405] New: enums can be long in gcc-13 jirislaby at gmail dot com
2022-10-26  4:28 ` [Bug c/107405] enums can be wrongly long in gcc-13 (in gnu99) jirislaby at gmail dot com
2022-10-26  6:55 ` marxin at gcc dot gnu.org
2022-10-26  7:08 ` marxin at gcc dot gnu.org
2022-10-26  7:27 ` jirislaby at gmail dot com
2022-10-26  7:31 ` jirislaby at gmail dot com
2022-10-26  7:45 ` jakub at gcc dot gnu.org
2022-10-26  7:53 ` jirislaby at gmail dot com
2022-10-26  8:04 ` jakub at gcc dot gnu.org
2022-10-26  8:21 ` redi at gcc dot gnu.org
2022-10-26  8:39 ` jirislaby at gmail dot com
2022-10-26  8:49 ` jirislaby at gmail dot com
2022-10-26 16:55 ` [Bug c/107405] [13 Regression] enum change causing Linux kernel to fail to build due to Linux depending on old behavior pinskia at gcc dot gnu.org
2022-10-26 17:35 ` joseph at codesourcery dot com
2022-10-28 11:19 ` rguenth at gcc dot gnu.org
2022-11-19  8:43 ` jakub at gcc dot gnu.org
2022-11-19 13:18 ` macro at orcam dot me.uk
2022-11-19 20:46 ` jakub at gcc dot gnu.org
2022-11-21 18:10 ` joseph at codesourcery dot com
2022-11-22 14:53 ` macro at orcam dot me.uk [this message]
2022-11-22 22:47 ` joseph at codesourcery dot com
2022-11-29 14:57 ` pinskia at gcc dot gnu.org
2023-01-13 11:36 ` rguenth at gcc dot gnu.org
2023-03-24  9:27 ` rguenth at gcc dot gnu.org

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