Comma operator initialization bug in MSVC compiler

repro.c

#include <inttypes.h>
#include <stdio.h>

typedef struct
{
    uint64_t a;
    uint64_t b;
} s_t;

s_t s = {
     0x7bd9d3ae0409903aULL,
    (0, 0x7bd9d3ae0409903aULL),
};

int main(int argc, char **argv)
{
    s_t t = {
      0x7bd9d3ae0409903aULL,
      (0, 0x7bd9d3ae0409903aULL),
    };
    printf("s.a = %" PRIx64 "\n", s.a);
    printf("s.b = %" PRIx64 "\n", s.b);
    printf("t.a = %" PRIx64 "\n", t.a);
    printf("t.b = %" PRIx64 "\n", t.b);
}

/*
When compiled as .c this produces the output:

	s.a = 7bd9d3ae0409903a
	s.b = 409903a
	t.a = 7bd9d3ae0409903a
	t.b = 7bd9d3ae0409903a

When compiled as .cpp this produces the expected output:

	s.a = 7bd9d3ae0409903a
	s.b = 7bd9d3ae0409903a
	t.a = 7bd9d3ae0409903a
	t.b = 7bd9d3ae0409903a
*/