vk_compute_demo: replace usage guards with #ifndef fallback defines

The #if defined(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME) guards
fixed the compile error on old Vulkan SDK headers but silently removed
the runtime portability detection on those headers — breaking macOS /
MoltenVK on any machine with an SDK older than 1.3.x.

The correct fix is to define local fallback constants when the header
doesn't provide them. Both values are fixed by the Vulkan spec, so
hardcoding them as fallbacks is safe across all SDK versions. The
runtime detection and flag assignment are now always compiled and
always run; on old-header Linux the strcmp never matches at runtime
(the extension isn't present there), so hasPortabilityEnum stays false
and behaviour is unchanged.

Also removes the (void)hasPortabilityEnum bandaid that the usage guards
had introduced.

Author: jvepsalainen-nv

examples/shader-coverage-bvh-traversal/vk_compute_demo.cpp

@@ -6,6 +6,16 @@
 
 #include <cstring>
 
+// VK_KHR_portability_enumeration was introduced in Vulkan SDK 1.3.x headers.
+// Define string and flag fallbacks so the runtime detection below compiles
+// against any SDK version; both values are fixed by the Vulkan spec.
+#ifndef VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME
+#define VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME "VK_KHR_portability_enumeration"
+#endif
+#ifndef VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR
+#define VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR ((VkInstanceCreateFlagBits)0x00000001)
+#endif
+
 namespace vkdemo
 {
 
@@ -18,10 +28,6 @@ void Context::init(bool requireInt64Atomics)
     std::vector<VkExtensionProperties> props(propertyCount);
     vkEnumerateInstanceExtensionProperties(nullptr, &propertyCount, props.data());
     bool hasPortabilityEnum = false;
-    // VK_KHR_portability_enumeration is only defined by Vulkan headers >= 1.3.x.
-    // Guard the references so older headers (e.g. on some Linux CI runners) still
-    // compile; the runtime detection runs wherever the extension is available.
-#if defined(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME)
     for (auto& p : props)
     {
         if (std::strcmp(p.extensionName, VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME) == 0)
@@ -31,7 +37,6 @@ void Context::init(bool requireInt64Atomics)
             break;
         }
     }
-#endif
 
     VkApplicationInfo appInfo = {};
     appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
@@ -50,11 +55,8 @@ void Context::init(bool requireInt64Atomics)
     ci.pApplicationInfo = &appInfo;
     ci.enabledExtensionCount = (uint32_t)instanceExts.size();
     ci.ppEnabledExtensionNames = instanceExts.data();
-#if defined(VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR)
     if (hasPortabilityEnum)
         ci.flags = VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR;
-#endif
-    (void)hasPortabilityEnum; // unused when the portability headers are absent
     check(vkCreateInstance(&ci, nullptr, &instance), "vkCreateInstance");
 
     // Pick a physical device with a compute-capable queue family. When 64-bit

examples/shader-coverage-image-pipeline/vk_compute_demo.cpp

@@ -6,6 +6,16 @@
 
 #include <cstring>
 
+// VK_KHR_portability_enumeration was introduced in Vulkan SDK 1.3.x headers.
+// Define string and flag fallbacks so the runtime detection below compiles
+// against any SDK version; both values are fixed by the Vulkan spec.
+#ifndef VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME
+#define VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME "VK_KHR_portability_enumeration"
+#endif
+#ifndef VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR
+#define VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR ((VkInstanceCreateFlagBits)0x00000001)
+#endif
+
 namespace vkdemo
 {
 
@@ -18,10 +28,6 @@ void Context::init(bool requireInt64Atomics)
     std::vector<VkExtensionProperties> props(propertyCount);
     vkEnumerateInstanceExtensionProperties(nullptr, &propertyCount, props.data());
     bool hasPortabilityEnum = false;
-    // VK_KHR_portability_enumeration is only defined by Vulkan headers >= 1.3.x.
-    // Guard the references so older headers (e.g. on some Linux CI runners) still
-    // compile; the runtime detection runs wherever the extension is available.
-#if defined(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME)
     for (auto& p : props)
     {
         if (std::strcmp(p.extensionName, VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME) == 0)
@@ -31,7 +37,6 @@ void Context::init(bool requireInt64Atomics)
             break;
         }
     }
-#endif
 
     VkApplicationInfo appInfo = {};
     appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
@@ -50,11 +55,8 @@ void Context::init(bool requireInt64Atomics)
     ci.pApplicationInfo = &appInfo;
     ci.enabledExtensionCount = (uint32_t)instanceExts.size();
     ci.ppEnabledExtensionNames = instanceExts.data();
-#if defined(VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR)
     if (hasPortabilityEnum)
         ci.flags = VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR;
-#endif
-    (void)hasPortabilityEnum; // unused when the portability headers are absent
     check(vkCreateInstance(&ci, nullptr, &instance), "vkCreateInstance");
 
     // Pick a physical device with a compute-capable queue family. When 64-bit