bit field struct is wrong size when compiled with wpp386 but not wcc386

[ideafarm]

struct
{
unsigned long long ii1 : 24 ;
unsigned long long ii2 : 24 ;
unsigned long long ii3 : 9 ;
}
foo ;

unsigned c1 = sizeof foo ;

int main( void )
{
return 0 ;
}

---

wpp386 -d2 -zp1 bench.cpp -q
wcc386 -d2 -zp1 bench.c -q

when compiled with wcc386, sizeof foo is 8 (correct).
when compiled with wpp386, sizeof foo is 0xc (wrong).
OW2 is at commit 83fb416, which is 3 commits behind current as of this writing.

Priority: This bug affects code that uses Windows structure MIB_UNICASTIPADDRESS_ROW, such as CreateUnicastIpAddressEntry(). (See the member InterfaceLuid.) The likely impact of this bug is that any structure (or class or union) that contains a bit field of the type unsigned long long will have members misaligned, which will generally be fatal if the structure is used to communicate with an operating system api.

[jmalak]

Thank you for your bug report.
I confirm it is bug in C++ compiler.
The OW extension for 64-bit bitfields was implemented/fixed for C compiler only.
C++ compiler use only 32-bit size bitfields compression.
C++ compiler OW extension for bitfields must be reworked completely to support 64-bit size bitfield compression.

In your case C++ compiler uses 3 x 32-bit bits = 12 bytes, C compiler uses 1x 64-bit bits = 8 bytes.