From: Sam James <sam@gentoo.org>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: arnold@skeeve.com, Gnulib bugs <bug-gnulib@gnu.org>,
concord@gentoo.org, bug-gawk@gnu.org
Subject: Re: Clang-built Gawk 5.2.1 regex oddity
Date: Tue, 3 Jan 2023 02:43:14 +0000 [thread overview]
Message-ID: <928FEE7D-2F32-4952-A6F8-681BBE8DA914@gentoo.org> (raw)
In-Reply-To: <F4F78F36-49A9-4FB0-BF95-1984AF1FB6D1@gentoo.org>
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> On 3 Jan 2023, at 02:14, Sam James <sam@gentoo.org> wrote:
>
>
>
>> On 2 Jan 2023, at 06:10, Paul Eggert <eggert@cs.ucla.edu> wrote:
>>
>> This is a serious bug in Clang: it generates incorrect machine code.
>>
>> [snip]
>>
>> My guess is that Clang got confused because dfaerror is declared _Noreturn, so Clang mistakenly assumed that dfawarn is also _Noreturn, which it is not.
>>
>> I worked around the Clang bug by installed the attached patch into Gnulib. Please give it a try with Gawk.
>
> Confirmed this mitigates the problem. I had to apply it manually to support/ as I couldn't immediately see how to sync gnulib myself, but that's no big deal.
>
>>
>> Incorrect code generation is a serious bug in Clang; can you please report it to the Clang folks? I am considering using a bigger hammer, and doing this:
>>
>
> Kenton's done this at https://github.com/llvm/llvm-project/issues/59792 now.
>
>> #define _Noreturn /*empty*/
>>
>> whenever Clang is used, until the bug is fixed.
>>
>
> maskray's analysis so far at https://github.com/llvm/llvm-project/issues/59792#issuecomment-1369314436 agrees with yours, which would mean
> this is likely a good idea.
>
By the way, when I ran gnulib's test suite following https://sourceware.org/glibc/wiki/Testing/Gnulib, I didn't get any failures
with Clang. I was expecting to get one (before your commit) for DFA.
Maybe we should shoehorn a similar ternary expression into tests/test-dfa-match-aux.c so we're guaranteed
a test failure with bad compilers if someone uses the DFA module?
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next prev parent reply other threads:[~2023-01-03 2:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20221230000119.hyui6umnspuyzqum@bubbles>
[not found] ` <202212300913.2BU9DV6V030160@freefriends.org>
[not found] ` <6DADB0FC-87EE-4028-91DF-C93A968A8982@gentoo.org>
2023-01-01 19:06 ` Clang-built Gawk 5.2.1 regex oddity arnold
2023-01-02 6:10 ` Paul Eggert
2023-01-03 2:14 ` Sam James
2023-01-03 2:43 ` Sam James [this message]
2023-01-05 23:06 ` Arsen Arsenović
2023-01-06 12:21 ` arnold
2023-01-13 7:03 ` Sam James
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