malloc error when trying to assign the returned pointer to a struct field

[rempas]

On Friday, 8 September 2023 at 19:14:47 UTC, H. S. Teoh wrote:
> The error message looks to me like a corruption of the malloc 
> heap. These kinds of bugs are very hard to trace, because they 
> may go undetected and only show up in specific circumstances, 
> so small perturbations of completely unrelated code may make 
> the bug appear or disappear -- just because the bug doesn't 
> show up when you disable some code does not prove that that's 
> where the problem is; it could be that corruption is still 
> happening, it just so happens that it goes unnoticed when the 
> behaviour of the code changes slightly.

Yep! That's what I guess as well! Tbh, I knew that playing with 
memory and trying to write a system library will be a touch job 
and I'm up for it! But these bugs really burn me out because like 
you said, nobody can truly help because they are so weird...

> My guess is that you have a double-free somewhere, or there's a 
> buffer overrun. Or maybe some bad interaction with the GC, e.g. 
> if you tried to free a pointer from the GC heap. (Note that 
> this may not immediately show up; free() could've assumed that 
> everything was OK when it has in fact messed up its internal 
> data structures; the problem would only show up later on in 
> code that's actually unrelated to the real problem.)

I have commented out every `free` at this point just to be sure 
and still the problem remains. I don't know what a "buffer 
overrun" is, I will make my research and I will reply you when I 
try. The GC does not exist as I'm `betterC`.

> If I were in your shoes I'd use Valgrind / Memcheck to try to 
> find the real cause of the problem.  Chances are, it may have 
> nothing to do with the bit of code you quoted at all.  You 
> could try to insert extra malloc/free's in various places 
> around the code (in places along the code path, but unrelated 
> to the problematic code) to see if that changes the behaviour 
> of the bug. If it does, your corruption is likely somewhere 
> other than the _ptr code you showed.
>
>
> T

Thanks for the advice! I already used Valgrind before I bother 
you guys but because at this point of development, I didn't cared 
about freeing the memory, "valgrind" points so many errors that 
it isn't useful to help me identify what's wrong.