Overlapping red/write of union is undefined behavior

[vix]

I have this struct/union, to have a bitwise access in C99 codebase (not C++)

typedef union {
    struct {
        uint32_t a:1;
        uint32_t b:1;
        uint32_t c:1;
        uint32_t d:29;
    };
    uint32_t    u32;
} MyStruct;

MyStruct m;

When I do

m.a = m.b = m.c = 0;

cppcheck gives "Overlapping red/write of union is undefined behavior".
Not sure if this is a real problem or a false positive.

Can someone give an advise?

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/11013