common.h: Make IS_ALIGNED() safe for testing with alignment == 0

[jsarha]

Make IS_ALIGNED() safe for testing with alignment == 0. Without this fix the DSP will crash if alignemnet is 0.

This is why:

The current virtual heap implementation has this line:
assert(IS_ALIGNED(mem, align));

And mod_balloc() implementation looks like this:
static inline void *mod_balloc(struct processing_module *mod, size_t size)
{
return mod_balloc_align(mod, size, 0);
}

Which means, that without this fix any call to mod_balloc() would cause division by zero crash.

I think the correct place to fix this error is in IS_ALIGNED() macro. It should not crash if someone wants to check alignment to zero.

[Copilot]

Pull Request Overview

This PR fixes a division-by-zero crash in the IS_ALIGNED() macro that occurs when checking alignment with a value of 0. The issue manifests when mod_balloc() calls mod_balloc_align() with align=0, which then triggers an assertion using IS_ALIGNED() that would perform a modulo operation by zero.

Key Changes:

• Modified IS_ALIGNED() macro to handle zero alignment values safely by short-circuiting when alignment is 0

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[Copilot]

The macro lacks documentation explaining the behavior when alignment is 0. Add a comment clarifying that zero alignment is treated as always aligned (returns true), which prevents division by zero in the modulo operation.

Suggested change

	/* Align the number to the nearest alignment value */
	/* Align the number to the nearest alignment value */
	/* If alignment is zero, IS_ALIGNED returns true (treats all values as aligned).
	* This prevents division by zero in the modulo operation.
	*/

[abonislawski]

I think we are using Zephyr version (included above) and this version of IS_ALIGNED wont be used (#ifndef IS_ALIGNED)

#ifdef __ZEPHYR__
#include <zephyr/sys/util.h>
#endif

btw alignment 0 is incorrect anyway so maybe this macro was called somewhere where it shouldnt?

[jsarha]

Whether it is incorrect or not, is a matter of definition. But apparently this change is useless on its own, so I'll close it.

[jsarha]

The Zephyr definition is the one that is used in SOF, not this. So this is an idle attempt to fix the issue.