[Bug 53960] New: ucrt has different struct layout than msvcrt

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=53960

Bug ID: 53960
           Summary: ucrt has different struct layout than msvcrt
           Product: Wine
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: msvcrt
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

https://bugs.winehq.org/show_bug.cgi?id=51698

I found that bug before it was actually because UCRT definition of struct
_iobuf in wine is just wrong.

This is a serious abi issue that has to be fixed and that is also probably why
UCRT programs do not work very well on wine.

/*
referenced from win10sdk ucrt
C:\Program Files (x86)\Windows Kits\10\Source\10.0.19041.0\ucrt
//-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
// Internal Stream Types (__crt_stdio_stream and friends)
//
//-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Ensure that __crt_stdio_stream_data* and FILE* pointers are freely
convertible:
struct ucrt_stdio_stream_data
{
    union
    {
        FILE  public_file;
        char* ptr;
    };
    char*            base;
    int              cnt;
    long             flags;
    long             file;
    int              charbuf;
    int              bufsiz;
    char*            tmpfname;
};

The definition of UCRT is

struct
#if __has_cpp_attribute(__gnu__::__may_alias__)
[[__gnu__::__may_alias__]]
#endif
ucrt_iobuf
{
    char*         _ptr;
    char*            _base;
    int              _cnt;
    long             _flag;
    long             _file;
    int              _charbuf;
    int              _bufsiz;
    char*            _tmpfname;
};

while msvcrt is

struct
#if __has_cpp_attribute(__gnu__::__may_alias__)
[[__gnu__::__may_alias__]]
#endif
ucrt_iobuf
{
  char* _ptr;
  int   _cnt;
  char* _base;
  int   _flag;
  int   _file;
  int   _charbuf;
  int   _bufsiz;
  char* _tmpfname;
};

The location of _base and _cnt swaps.