The following derives from [this](Implicit type casting within parenthesis and literals in C) question but is distinct

Consider the following code sample;

```

uint32_t *value = malloc(sizeof(uint32_t));

*value = 0xAAAABBBB;

int16_t *subset = (int16_t*) (value);

uint32_t test = 0x00000000;

uint32_t test2 = 0x00000000;

// IMPORTANT!!!!

// *subset vs *subset & 0xFFFF

test = (*subset << 16) | *subset & 0xFFFF;

test2 = (*subset << 16) | *subset;

// Test: 0xbbbb bbbb

// Test2: 0xffff bbbb

```

As you can see, subset is only 16 bits wide. As such (and as commenters on the previous post stated_, & 0xFFFF is redundant since the type is only 16 bit.

This is incorrect and when tested on my compiler (gcc 15.2.1 on Linux AND gcc for noabi arm), the & operator acts outside the bitlength of *subset to the bit length of the literal 0xFFFF (which I believe from the answers to the previous question is 32), thus acting on bits which are -16 from the address of subset.

Is this a bug in GCC or is this within spec? Also why are first 16 bits FFFF?

Note: My system is little endian