Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior
| От | Ranier Vilela |
|---|---|
| Тема | Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior |
| Дата | |
| Msg-id | CAEudQArZaGP8Sr7EvTMLL47AQU8Ei0yZqX=zGLRg592LUuc92A@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior (Alvaro Herrera <alvherre@2ndquadrant.com>) |
| Ответы |
Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior
|
| Список | pgsql-hackers |
Em seg., 31 de ago. de 2020 às 14:00, Alvaro Herrera <alvherre@2ndquadrant.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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