• d-bugmail puremagic.com (68/68) Jun 22 https://issues.dlang.org/show_bug.cgi?id=24624

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=24624

          Issue ID: 24624
           Summary: Struct with both bitfields and a slice or class
                    instance ref doesn't compile.
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: jonas.meeuws gmail.com

Compiling the following code with -preview=bitfields:
---
struct S
{   
    char[] slice;
    bool flag:1;
}
---
Produces: "Error: cannot take address of bit-field `flag`".

After experimenting it seems that:
  - A struct with bitfields cannot contain:
    - Slices of any type.
    - Class instance references.
    - Structs, enums or references to classes containing any of the above.
  - Bitfields in classes or named unions are not affected.
  - When wrapping the bitfields in a named struct, the issue doesn't happen.
  - With -betterC or ldcs --fno-rtti, the issue doesn't happen.
    The issue might involve TypeInfo_Struct?

More failing examples:
---
struct S1
{
    bool flag:1;
    Object o;
}

struct Wrapper2
{
    void[] wrapped;
}
struct S2
{
    bool flag:1;
    Wrapper2 wrapper;
}

struct Wrapper3
{
    Object wrapped;
}
struct S3
{
    bool flag:1;
    Wrapper3 wrapper;
}

enum Wrapper4 : string
{
    empty = ""
}
struct S4
{
    bool flag:1;
    Wrapper4 wrapper;
}
---

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