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Re: [lmi] UBSAN flags


From: Greg Chicares
Subject: Re: [lmi] UBSAN flags
Date: Tue, 7 Jun 2022 23:29:15 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0

On 6/7/22 01:04, Vadim Zeitlin wrote:
> On Mon, 6 Jun 2022 23:46:41 +0000 Greg Chicares <gchicares@sbcglobal.net> 
> wrote:
> 
> [...compilation error with -O3...]
[...]
> GC> Dare we consider the possibility that UBSan is malfunctioning?
> 
>  I think it's a compiler bug, not UBSAN's, but somehow it's only triggered
> by the latter. FWIW it still compiles with ASAN and it also compiles with
> UBSAN when using clang.

Thanks: strong evidence that it's a false positive with gcc -O3.

>  BTW, compiling this single source file with -O3 takes 15 seconds on my
> machine with g++-12, which is even slower than the already not great 14s
> with g++-11.

That seems to fit the general trend, and 15s vs. 14s isn't awful.

> amazingly, fails to compile with yet another
> warning (-Wmaybe-uninitialized this time) with g++-12.

If you see legitimate warnings with g++-12, I'd be happy to fix
them now.


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