• d-bugmail puremagic.com (27/27) Mar 29 2022 https://issues.dlang.org/show_bug.cgi?id=22955

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=22955

          Issue ID: 22955
           Summary: importC: wrong alignof for D struct with specified
                    alignment
           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" );

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