From: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
---|---|
To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Geoghegan <pg(at)bowt(dot)ie>, Noah Misch <noah(at)leadboat(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior |
Date: | 2020-08-31 17:43:56 |
Message-ID: | CAEudQArZaGP8Sr7EvTMLL47AQU8Ei0yZqX=zGLRg592LUuc92A@mail.gmail.com |
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Lists: | pgsql-hackers |
Em seg., 31 de ago. de 2020 às 14:00, Alvaro Herrera <
alvherre(at)2ndquadrant(dot)com> escreveu:
> On 2020-Aug-31, Ranier Vilela wrote:
>
> > More troubles with undefined-behavior.
> >
> > This type of code can leaves overflow:
> > var = (cast) (expression);
> > diff = (int32) (id1 - id2);
> >
> > See:
> > diff64 = ((long int) d1 - (long int) d2);
> > diff64=-4294901760
>
> Did you compile this with gcc -fwrapv?
>
gcc 10.2 -O2 -fwrapv
bool test1()
{
unsigned int d1 = 3;
unsigned int d2 = 4294901763;
long int diff64 = 0;
diff64 = ((long int) d1 - (long int) d2);
return (diff64 < 0);
}
output:
mov eax, 1
ret
What is a workaround for msvc 2019 (64 bits) and clang 64 bits (linux)?
transam.c:311:22: runtime error: unsigned integer overflow: 3 - 4294901763
cannot be represented in type 'unsigned int'
Ranier Vilela
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