[NSWI004] How to cause segmentation fault.

[Tomáš Kubíček]

You can maybe write your own assert which calls the predefined assert when
compiled with KERNEL_DEBUG flag, and otherwise casts it to void, to avoid
the unused error

On Fri, 30 Oct 2020 at 19:57, Jura Pelc <jirik.pelc1998 at gmail.com> wrote:

> 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
> _______________________________________________
> NSWI004 mailing list
> NSWI004 at d3s.mff.cuni.cz
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>
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