[musl] Re: realloci(): A realloc() variant that works in-place

[Andreas Schwab]

On Okt 31 2025, Thiago Macieira wrote:

> But I think any such thing would be extremely fragile. Very low-level library 
> authors can probably get it right, but I wouldn't trust this feature to more 
> than a few dozen people on the planet. We're talking about something like:
>
> void adjust_after_relocation(T *object, uintptr_t old) // or ptr_bits<T>
>
> The temptation is too great to cast the old to a T* and dereference it, which 
> is UB because the memory has been freed, but will "happen to work" for 
> sufficiently many executions that it might go unnoticed. Then there's the issue 
> that the relocated T *object is itself in an inconsistent state and one must 
> avoid calling most functions on it.

And it will not be thread safe.  The freed memory can be allocated to
another thread any time.

-- 
Andreas Schwab, schwab@linux-m68k.org
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