Bad warning or not

Question

In SunStudio12 rh4, I get the following warning
"/xxx.h", line 92: Warning: Types cannot be declared in anonymous union.
Code is from
union
struct
double xStart; /* 256 - 263 */
double xDelta; /* 264 - 271 */
uint32_t xUnits; /* 272 - 275 */
} adjunct_1000;
struct
double rowStart; /* 256 - 263 */
double rowDelta; /* 264 - 271 */
uint32_t rowUnits; /* 272 - 275 */
uint32_t columnRecs; /* 276 - 279 */
double columnStart; /* 284 - 291 */
double columnDelta; /* 292 - 299 */
uint32_t columnUnits; /* 300 - 303 */
} adjunct_2000;
struct
struct
double tagStart; /* 256 - 263 */
double tagDelta; /* 264 - 271 */
uint32_t tagUnits; /* 272 - 275 */
uint32_t numberSubrec; /* 276 - 279 */
double r2Start; // 280 - 287 | Unused. Set to tagStart.
double r2Delta; // 288 - 295 | Unused. Set to tagDelta.
uint32_t r2Units; // 296 - 299 | Unused. Set to tagUnits.
uint32_t recordLength; /* 300 - 303 */
struct
char name [4];
char format[2];
uint16_t offset;
} subr[26];
} adjunct_3000;
I think this is legal. IBM's web site certainly seems to say this is ok. (this is within a big structuer).
Comments?

Answer 1

There are two separate issues.
1. An anonymous union at global or namespace scope must be declared static.
2. An anonymous union cannot declare nested types.
Your original example showed an anonymous union at global scope that was not declared static, and that declared nested types.
You later revised the example to show the anonymous union as a member of a struct, but it still declared nested types.
Your new example is similar to the revised example. The anonymous union is a member of a struct, which is always OK. But the anonymous union declares two nested structs, which is not OK.
You can make the example valid by naming the structs and moving them outside the anonymous union:
struct S1 {
int b;
int c;
struct S2 {
int d;
int e;
struct my_struct {
int a;
union {
S1 s1;
S2 s2;
or like this, to preserve some scope:
struct my_struct {
int a;
struct S1 {
int b;
int c;
struct S2 {
int d;
int e;
union {
S1 s1;
S2 s2;
};