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From: "yy172179 at 163 dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107339] RISC V -mstrict-align
Date: Fri, 21 Oct 2022 05:21:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107339

--- Comment #2 from yy <yy172179 at 163 dot com> ---
(In reply to Andrew Pinski from comment #1)
> The code is broken.
>=20
> uint32_t here is aligned to 32bits and you access it via that type.
>=20
>=20
> this is the correct fix:
>=20
>=20
> typedef uint32_t uint32_t_ua __attribute__((aligned(1)));
>=20
> void  tttt (misalign_t* t){
>=20
>     printf("%x\n",(*(const uint32_t_ua *)&t->rseq[0]));
>     printf("%x\n",(*(const uint32_t_ua *)&t->rseq[1]));
> }
(In reply to Andrew Pinski from comment #1)
> The code is broken.
>=20
> uint32_t here is aligned to 32bits and you access it via that type.
>=20
>=20
> this is the correct fix:
>=20
>=20
> typedef uint32_t uint32_t_ua __attribute__((aligned(1)));
>=20
> void  tttt (misalign_t* t){
>=20
>     printf("%x\n",(*(const uint32_t_ua *)&t->rseq[0]));
>     printf("%x\n",(*(const uint32_t_ua *)&t->rseq[1]));
> }
Maybe I didn't make the problem clear. To add, I think the non aligned addr=
ess
"lw" will be converted to "lbu" to access this address indirectly. Change t=
he
above code parameters to the structure, and the situation I think is correct
will occur.

#include<stdio.h>

typedef  struct  __attribute__((packed)) misalign
{
    uint8_t rseq[16];
    uint8_t type;
    uint8_t cnt;
} misalign_t;
void  tttt (misalign_t t){

    printf("%x\n",(*(const uint32_t*)&t.rseq[0]));
    printf("%x\n",(*(const uint32_t*)&t.rseq[1]));
}
int main()
{

    misalign_t  abc;
    misalign_t *test=3D&abc;
    tttt(abc);
        while(1);=20
   }=