The address of local variable x is accessed at non-zero index

[Tom]

I am using Cppcheck 2.1 and I get an error indicating 'the address of location variable "checksum" is accessed at non-zero index'.

Here is the code:

void functionA(void)
{
    uint32_t checksum = adler32(checksum, buf_ptr, len);

    checksum = ((((uint8_t*)&checksum)[0u] << 24u) + (((uint8_t*)&checksum)[1u] << 16u) + (((uint8_t*)&checksum)[2u] << 8u) + ((uint8_t*)&checksum)[3u]);
}

This looks like a false positive to me?!

[CHR]

I can reproduce this with v2.3 and head.

[CHR]

I have created a ticket: https://trac.cppcheck.net/ticket/10156

Out of curiosity, I tried to rewrite that code to make it more readable. At least in clang, all the variants become equivalent at -O3: https://godbolt.org/z/6q49sY
And I know that the union trick is UB, but the major compilers accept it anyway.