[NSWI004] How to cause segmentation fault.

[Jura Pelc]

I am sorry to reopen the closed questions but assert does not suit my
problem.
following code is compilable when debugging, but is incompilable during
test run because of unused variable `free_block`:
```c
    freelist_item_t* free_block = claim_block_free((uintptr_t)header,
header->size);
    assert(free_block != NULL);
```

```shell
src/mm/heap.c:323:22: error: unused variable 'free_block'
[-Werror=unused-variable]
  323 |     freelist_item_t* free_block =
claim_block_free((uintptr_t)header, header->size);
      |
```

So basically I need the equivalent of `assert` but for both debug and test
runtime.

pá 30. 10. 2020 v 19:12 odesílatel Petr Tuma <petr.tuma at d3s.mff.cuni.cz>
napsal:

> Hi,
>
> I guess your point is how to do an equivalent of an `assert` statement
> (that is, announce a fatal error and stop the execution) ? For that, there
> already is an `assert` macro in `debug.h` ... or did you have something
> else in mind ?
>
> Petr
>
>
> On 30/10/2020 18:55, Jura Pelc wrote:
> > Hello,
> >
> > I am working on the implementation of free and I come across a conflict
> between me as a C# programer and kernel C code.
> > ```c
> > if((uintptr_t)ptr < heap_begin || (uintptr_t)ptr > heap_end)
> > {
> >      //TODO: segmentation fault
> >      return;
> > }
> > ```
> > I want to safely determine that the user is dum and trying to free some
> unknown memory.
> > For this, I can see some kind of range check for free and "throwing"
> segmentation fault as interop.
> > I was thinking about
> https://www.tutorialspoint.com/c_standard_library/c_function_raise.htm <
> https://www.tutorialspoint.com/c_standard_library/c_function_raise.htm>,
> but I did not found this is the kernel.
> >
> > So my question is, how to raise segmentation fault during free safely?
> >
> > --
> >
> > S pozdravem Jiří Pelc
> > Matematicko-fyzikální fakulta
> > Univerzita Karlova
> >
> > _______________________________________________
> > NSWI004 mailing list
> > NSWI004 at d3s.mff.cuni.cz
> > https://d3s.mff.cuni.cz/mailman/listinfo/nswi004
> >
>


-- 

S pozdravem Jiří Pelc
Matematicko-fyzikální fakulta
Univerzita Karlova
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