[llvm-bugs] [Bug 43983] New: Alignment specifier not applied to anonymous structure or union

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43983

            Bug ID: 43983
           Summary: Alignment specifier not applied to anonymous structure
                    or union
           Product: clang
           Version: 9.0
          Hardware: Macintosh
                OS: MacOS X
            Status: NEW
          Severity: normal
          Priority: P
         Component: C
          Assignee: unassignedclangbugs at nondot.org
          Reporter: omrimor2 at illinois.edu
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Created attachment 22802
  --> https://bugs.llvm.org/attachment.cgi?id=22802&action=edit
minimal example

The _Alignas specifier is not being applied to anonymous structures or unions.
If the structure or union is given a declarator then the alignment specifier is
correctly applied. This is a useful construct in that it allows for alignment
of portions of a structure.

#include <stdio.h>

struct A {              struct { int a; };   };
struct B { _Alignas(64) struct { int b; };   };
struct C { _Alignas(64) struct { int c; } x; };

int main(int argc, char *argv[])
{
        printf("%zu %zu %zu\n",
               sizeof(struct A), sizeof(struct B), sizeof(struct C));
        return 0;
}

Should output "4 64 64" on an LP64 platform; instead outputs "4 4 64". GCC 9
compiles correctly. I haven't yet tested on platforms other than macOS.

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