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* [Bug c/101925] New: reversed storage order when compiling with -O3 only
@ 2021-08-15 23:43 george.thopas at gmail dot com
  2021-08-15 23:50 ` [Bug tree-optimization/101925] " pinskia at gcc dot gnu.org
                   ` (12 more replies)
  0 siblings, 13 replies; 14+ messages in thread
From: george.thopas at gmail dot com @ 2021-08-15 23:43 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101925

            Bug ID: 101925
           Summary: reversed storage order when compiling with -O3 only
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: george.thopas at gmail dot com
  Target Milestone: ---

/*
     reversed storage order when compiling with -O3 only. 
     this time sets up an all big-endian struct 
     from an all little-endian one
     no warnings 

     Target: x86_64-pc-linux-gnu
     gcc versie 11.1.0 (Gentoo 11.1.0-r2 p3) 
     gcc-trunk too

     $ gcc -Wall -Wextra -O3 test.c 
     $ ./a.out 
     Abort 

 */


#define BIG_ENDIAN   __attribute__((scalar_storage_order("big-endian")))

/* host order version (little endian)*/
struct _ip6_addr {
    union {
        char addr8[16];
        int  addr32[4];
    } u;
};

typedef struct _ip6_addr t_ip6_addr;

struct _net_addr {
    char is_v4;
    union {
        int        addr;
        t_ip6_addr addr6;
    } u;
};

typedef struct _net_addr t_net_addr;

/* big endian version */
struct _be_ip6_addr {
    union {
        char addr8[16];
    } BIG_ENDIAN u;
} BIG_ENDIAN;

typedef struct _be_ip6_addr t_be_ip6_addr;

struct _be_net_addr {
    char is_v4;
    union {
        t_be_ip6_addr addr6;
        int           addr;
    } BIG_ENDIAN u;
} BIG_ENDIAN;

typedef struct _be_net_addr t_be_net_addr;

/* convert */
t_be_ip6_addr be_ip6_addr(const t_ip6_addr ip6)
{
    t_be_ip6_addr rc = {
        .u.addr8[0] = ip6.u.addr8[0],
        .u.addr8[1] = ip6.u.addr8[1],
        .u.addr8[2] = ip6.u.addr8[2],
        .u.addr8[3] = ip6.u.addr8[3],
        .u.addr8[4] = ip6.u.addr8[4],
        .u.addr8[5] = ip6.u.addr8[5],
        .u.addr8[6] = ip6.u.addr8[6],
        .u.addr8[7] = ip6.u.addr8[7],
        .u.addr8[8] = ip6.u.addr8[8],
        .u.addr8[9] = ip6.u.addr8[9],
        .u.addr8[10] = ip6.u.addr8[10],
        .u.addr8[11] = ip6.u.addr8[11],
        .u.addr8[12] = ip6.u.addr8[12],
        .u.addr8[13] = ip6.u.addr8[13],
        .u.addr8[14] = ip6.u.addr8[14],
        .u.addr8[15] = ip6.u.addr8[15],
    };
    return rc;
}

t_be_net_addr be_net_addr(const t_net_addr ip)
{
    t_be_net_addr rc = {.is_v4 = ip.is_v4 };
    if (ip.is_v4) {
        rc.u.addr = ip.u.addr;
    } else {
        rc.u.addr6 = be_ip6_addr(ip.u.addr6);
    }
    return rc;
}

int main(void)
{
    t_be_net_addr out = { };

    t_net_addr in = {
        .is_v4 = 0,
        .u.addr6.u.addr8 =
            { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }
    };

    out = be_net_addr(in);

    // actually first 4 bytes are swapped
    if (in.u.addr6.u.addr8[0] != out.u.addr6.u.addr8[0])
        __builtin_abort();

    return 0;
}

^ permalink raw reply	[flat|nested] 14+ messages in thread
end of thread, other threads:[~2021-10-13 11:10 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-15 23:43 [Bug c/101925] New: reversed storage order when compiling with -O3 only george.thopas at gmail dot com
2021-08-15 23:50 ` [Bug tree-optimization/101925] " pinskia at gcc dot gnu.org
2021-08-16  8:08 ` [Bug tree-optimization/101925] [10/11/12 Regression] " marxin at gcc dot gnu.org
2021-08-16  8:22 ` [Bug tree-optimization/101925] [10/11/12 Regression] reversed storage order when compiling with -O3 only since r10-4742-g9b75f56d4b7951c6 rguenth at gcc dot gnu.org
2021-08-16  9:27 ` ebotcazou at gcc dot gnu.org
2021-08-16 10:45 ` rguenth at gcc dot gnu.org
2021-08-16 11:20 ` rguenth at gcc dot gnu.org
2021-08-16 12:20 ` ebotcazou at gcc dot gnu.org
2021-08-16 13:16 ` rguenther at suse dot de
2021-08-16 13:21 ` rguenth at gcc dot gnu.org
2021-08-17  7:25 ` cvs-commit at gcc dot gnu.org
2021-09-06  8:50 ` [Bug tree-optimization/101925] [10/11 " cvs-commit at gcc dot gnu.org
2021-10-13 11:09 ` [Bug tree-optimization/101925] [10 " cvs-commit at gcc dot gnu.org
2021-10-13 11:10 ` rguenth at gcc dot gnu.org

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