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digitalmars.D.bugs - [Issue 22955] New: importC: wrong alignof for D struct with


          Issue ID: 22955
           Summary: importC: wrong alignof for D struct with specified
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: ImportC
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: duser neet.fi
                CC: duser neet.fi

using the "align (16) struct __uint128_t" struct from __builtins.di:

_Static_assert( _Alignof(__uint128_t) == 16, "" ); // fail

it gives the size of a pointer (4 or 8), same as if align() wasn't used

it has the correct alignment in D:

import __builtins;
pragma(msg, __uint128_t.alignof); // 16

_Alignas() in C doesn't have the problem:

struct S { _Alignas(16) unsigned long long a; unsigned long long b; };
_Static_assert( _Alignof(struct S) == 16, "this works" );
_Static_assert( sizeof(struct S) == 16, "this works" );

Mar 29 2022