# Session Log — 2026-07-06

## Completed
- **Build system**: Fixed Just 1.55.1 `[working-directory]` bug (literal paths required).
  Set up `just build` for 6 object files: volk.c, wapp.c, pr_rhi_vk.c, pr_rhi_vk_vma.cpp,
  vulkan_profiles.cpp, main.cpp. Linked with `-lSDL3 -lglm -ltinyobjloader -lktx -lslang -lvulkan`.
- **RHI backend completeness**: Filled in all missing functions (profiles validation,
  swapchain/recreate, dynamic rendering, copy, queue submit, barriers, descriptor,
  pipeline, sync) — 68 functions total in single `pr_rhi_vk.c`.
- **Bugfix — `prRhiPresentVk`**: Used `current_image_index` from acquire instead of
  hardcoded `0`.
- **Bugfix — `extern "C"` linkage**: Added `extern "C"` guards in `pr_rhi.h` so C++
  callers (main.cpp) can link C-compiled backend symbols.
- **Bugfix — GPU name dangling pointers**: Added `device_name[256]`/`driver_info[256]`
  to `PrRhiPhysicalDevice` struct, populated during enumeration. Getters return pointers
  to these persistent buffers.
- **Bugfix — `volkInitialize()`**: Added call at start of `prRhiCreateInstanceVk` —
  `vpGetInstanceProfileSupport` crashed because volk hadn't loaded the Vulkan loader.
- **Bugfix — scratch arena OOM**: Changed initial 128KB → 64MB _and_ the line-320
  reinit override 8MB → 64MB. Prevents OOM during mesh building.
- **Bugfix — stale mesh array pointers**: Captured return values of `wpArrayAppendAlloc`
  in mesh-building loop — original code ignored the pointer, so `vertices`/`indices`
  pointed to stale initial array after regrowth.
- **Bugfix — uninitialised Vulkan stack arrays**: Zero-initialised all 18 local Vulkan
  struct array declarations (`VkImageMemoryBarrier2[16]`, `VkBufferMemoryBarrier2[16]`,
  `VkRenderingAttachmentInfo[8]`, `VkBufferImageCopy[16]`, plus `VkDescriptorSetLayout[8]`,
  `VkPushConstantRange[8]`, `VkVertexInputBindingDescription[8]`,
  `VkVertexInputAttributeDescription[16]`, `VkDynamicState[2]`, `VkFormat[8]`,
  `VkPipelineColorBlendAttachmentState[8]`, `VkDescriptorSetLayoutBinding[16]`,
  `VkDescriptorBindingFlags[16]`, `VkDescriptorPoolSize[8]`, `VkDescriptorImageInfo[16]`,
  `VkDescriptorBufferInfo[16]`, `VkFence[16]` (×2), `VkCommandBuffer[16]` (×2),
  `VkDescriptorSet[16]`, `VkBuffer[16]`). Uninitialised `pNext`/`imageOffset` fields
  caused GPU-side device-lost crashes.
- **Bugfix — `render_completed_semaphores` zero-length array**: `prRhiAcquireNextImage`
  returns swapchain image INDEX (0 on first call), not image count. Used as array capacity,
  this allocated 0 semaphores, causing out-of-bounds access in render loop → SIGSEGV.
  Fixed by reading `app.swapchain->image_count` instead.
- **Demo renders**: `build/prism` now launches a window, loads `suzanne0.ktx` / `suzanne1.ktx`,
  renders textured Suzanne mesh with mouse orbit + keyboard mesh selection.

## Key Decisions
- Just 1.55.1 bug: `[working-directory: '{{BUILDDIR}}']` causes "could not find the shell `sh`"
  — literal paths or no `[working-directory]` attribute required.
- VMA implementation in separate `pr_rhi_vk_vma.cpp` (compiled as C++).
- `PrRhiPhysicalDevice` stores `device_name[256]`/`driver_info[256]` to avoid dangling pointers.
- All stack Vulkan struct arrays must be `= {0}` initialised — C backend does not zero
  auto vars, and uninitialised `pNext`/offset fields cause GPU driver crashes.

## Next Steps
1. Review code for structural/design quality issues the user already noticed.
2. Add `wpMemArenaAllocatorTempBegin`/`TempEnd` markers around scratch allocations.
3. Consider adding `prRhiGetSwapchainImageCount` accessor for encapsulation.