CNA-BUG-196: CNA_X11_HAVE_VULKAN_HEADERS is defined by the X11 CMake but read by no source, so the dependency summary implies a Vulkan-header gate that does not exist

CNA snapshot 009d40f5  ·  Known Issues › Current bugs  ·  source links pinned to 009d40f5

PlatformX11.cmake defines CNA_X11_HAVE_VULKAN_HEADERS and lists Vulkan headers as an optional dependency, but no X11 source reads the macro; the X11 Vulkan surface is created unconditionally and resolves its entry point at run time.

Identifier

CNA-BUG-196

Category

Bug

Subsystem

Build & CI

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Severity

Low (a triage suggestion, not a project priority)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

None

Affected contract

cmake/PlatformX11.cmake's CNA_X11_HAVE_VULKAN_HEADERS definition and the X11 dependency summary

Expected behaviour

A compile definition that a CMake file publishes, and that its dependency summary presents as an optional Vulkan-header dependency, should gate something -- as the Wayland backend's CNA_WAYLAND_HAVE_VULKAN_HEADERS does, guarding WaylandVulkanSurface's construction.

Actual behaviour at TARGET

PlatformX11.cmake sets CNA_X11_HAVE_VULKAN_HEADERS=1 when find_package(Vulkan) finds headers and lists “Vulkan headers” as present/absent in the X11 dependency summary. No source reads CNA_X11_HAVE_VULKAN_HEADERS (only the Wayland macro is read, in WaylandPlatform.cpp): X11Platform::OpenConnection always constructs X11VulkanSurface, and capabilities.vulkanSurface is true whenever that object exists, because X11VulkanSurface restates the Vulkan structs locally and resolves vkCreateXlibSurfaceKHR at run time. So the X11 Vulkan surface does not depend on the headers at build time, and the summary's “Vulkan headers: present/absent” line implies a gate that does not exist.

Source locations

• cmake/PlatformX11.cmake — defines CNA_X11_HAVE_VULKAN_HEADERS and lists Vulkan headers in the summary
• modules/platform/src/X11/X11GraphicsServices.cpp — X11VulkanSurface restates the Vulkan structs and resolves vkCreateXlibSurfaceKHR at run time; reads no CNA_X11_HAVE_VULKAN_HEADERS
• modules/platform/src/X11/X11Platform.cpp — OpenConnection always creates vulkanSurface_; capabilities.vulkanSurface = (vulkanSurface_ != nullptr)

Evidence

Checked by reading PlatformX11.cmake and searching the whole tree for CNA_X11_HAVE_VULKAN_HEADERS (defined once, read nowhere; only CNA_WAYLAND_HAVE_VULKAN_HEADERS is consumed, in WaylandPlatform.cpp and cmake/Harnesses.cmake) at 009d40f5. Not executed. The Native Platforms guide already states that no X11 source reads the macro.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

No test or gate checks that a published platform compile definition is consumed.

Regression test

Remove CNA_X11_HAVE_VULKAN_HEADERS (and, if desired, drop “Vulkan headers” from the X11 summary or relabel it as build-time-optional-only), or make an X11 source consume it. A definition-usage lint would prevent the recurrence.

Blast radius

Maintainers reading the X11 dependency summary, who may conclude the X11 Vulkan surface needs the Vulkan headers at build time (it does not). The Wayland backend's equivalent macro is genuinely consumed and is unaffected.

Workaround

No workaround is known.