Re: What's "#<variable-code>"?

Found the issue.

I am populating a [VkPhysicalDeviceProperties](https://www.khronos.org/registry/vulkan/specs/1.1-extensions/man/html/VkPhysicalDeviceProperties.html) struct. On my system, C reports this structure as 824 bytes. (ctype-sizeof), on the other hand, says it's 312. Hardcoding 824 removed the error.

As for how this happened: My generated (define-cstruct) unconditionally declared members of struct instance types as pointers to those struct types.

Takeaway for visitors: Verify that sizes are correct by comparing output from C's sizeof with Racket's (ctype-sizeof).

~slg

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, October 23, 2019 11:04 AM, Sage Gerard <sage-nnKKxiom5Z1/[email protected]> wrote:

> Alright, thanks. I have a couple of leads on what happened, but since the implementation details are private I'm unsure of the best troubleshooting technique in this context.
>
> For now I am making a minimal C project that builds a shared library and follows the same allocation pattern and FFI use.
>
> I noticed that switching "_pointer" back to a tagged pointer type makes the program raise an error, but I suspect that's due to a tag being missing from the (malloc) call.
>
> Once I learn my mistake I will share it here.
>
> ~slg
>
> -------- Original Message --------
> On Oct 23, 2019, 10:58 AM, Sam Tobin-Hochstadt < [email protected]> wrote:
>
>> `#<variable-code>` is how a representation of one of the internal AST
>> types for the compiler is printed. When you see it, it definitely
>> means some memory got corrupted.
>>
>> Sam
>>
>> On Tue, Oct 22, 2019 at 4:52 PM Sage Gerard <sage-nnKKxiom5Z1/[email protected]> wrote:
>>>
>>> Here's a Vulkan app that prints the properties of the first physical device on the system: https://github.com/zyrolasting/racket-vulkan/blob/master/examples/mandelbrot.rkt#L39
>>>
>>> If you comment out the call to `vkGetPhysicalDeviceProperties`, the main module works. I create a Vulkan instance, print out a blank version of a struct, then destroy the instance. If I leave it in, I get:
>>>
>>> ; ptr-ref: contract violation
>>> ; expected: cpointer?
>>> ; given: #<variable-code>
>>> ; argument position: 1st
>>>
>>> I bind `vkGetPhysicalDeviceProperties` using _pointer so I can learn how to work with the raw API:
>>> https://github.com/zyrolasting/racket-vulkan/blob/master/unsafe.rkt#L1008
>>>
>>> I expect I misused a pointer and ended up with corrupted memory. But what is #<variable-code>, anyway? How did I produce it?
>>>
>>> ~slg
>>>
>>>
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