Vulkan: add context callback setters

Weak symbol overrides are not reliable in every embedding environment.

Add setter functions for the Vulkan acquire/release context callbacks, while keeping the existing weak symbols as the public runtime entry points. Passing null restores Halide's default context management.

Author: xFile3160

src/runtime/HalideRuntimeVulkan.h

@@ -106,6 +106,29 @@ extern int halide_vulkan_release_context(void *user_context,
                                          VkQueue queue,
                                          VkDebugUtilsMessengerEXT messenger);
 
+typedef int (*halide_vulkan_acquire_context_t)(void *user_context,
+                                               struct halide_vulkan_memory_allocator **allocator,
+                                               VkInstance *instance,
+                                               VkDevice *device,
+                                               VkPhysicalDevice *physical_device,
+                                               VkQueue *queue,
+                                               uint32_t *queue_family_index,
+                                               VkDebugUtilsMessengerEXT *messenger,
+                                               bool create);
+typedef int (*halide_vulkan_release_context_t)(void *user_context,
+                                               VkInstance instance,
+                                               VkDevice device,
+                                               VkQueue queue,
+                                               VkDebugUtilsMessengerEXT messenger);
+
+/** Override the Vulkan context acquisition callback. Returns the previous
+ * handler. If unset, Halide uses its built-in Vulkan context management.
+ */
+extern halide_vulkan_acquire_context_t halide_set_vulkan_acquire_context(halide_vulkan_acquire_context_t handler);
+
+/** Override the Vulkan context release callback. Returns the previous handler. */
+extern halide_vulkan_release_context_t halide_set_vulkan_release_context(halide_vulkan_release_context_t handler);
+
 /** Ensure a Halide Vulkan memory allocator exists for an externally-managed
  * Vulkan context. Intended for embedders that override
  * halide_vulkan_acquire_context()/halide_vulkan_release_context().

src/runtime/runtime_api.cpp

@@ -219,6 +219,8 @@ extern "C" __attribute__((used)) void *halide_runtime_api_functions[] = {
     (void *)&halide_vulkan_release_memory_allocator,
     (void *)&halide_vulkan_release_context,
     (void *)&halide_vulkan_run,
+    (void *)&halide_set_vulkan_acquire_context,
+    (void *)&halide_set_vulkan_release_context,
     (void *)&halide_webgpu_device_interface,
     (void *)&halide_webgpu_initialize_kernels,
     (void *)&halide_webgpu_finalize_kernels,

src/runtime/vulkan.cpp

@@ -42,17 +42,6 @@ ALWAYS_INLINE int vk_load_external_context_functions(void *user_context, VkInsta
     return halide_error_code_success;
 }
 
-}  // namespace Vulkan
-}  // namespace Internal
-}  // namespace Runtime
-}  // namespace Halide
-
-// --------------------------------------------------------------------------
-
-extern "C" {
-
-// --------------------------------------------------------------------------
-
 // The default implementation of halide_acquire_vulkan_context uses
 // the global pointers above, and serializes access with a spin lock.
 // Overriding implementations of acquire/release must implement the
@@ -65,15 +54,15 @@ extern "C" {
 //   call to halide_release_vulkan_context. halide_acquire_vulkan_context
 //   should block while a previous call (if any) has not yet been
 //   released via halide_release_vulkan_context.
-WEAK int halide_vulkan_acquire_context(void *user_context,
-                                       halide_vulkan_memory_allocator **allocator,
-                                       VkInstance *instance,
-                                       VkDevice *device,
-                                       VkPhysicalDevice *physical_device,
-                                       VkQueue *queue,
-                                       uint32_t *queue_family_index,
-                                       VkDebugUtilsMessengerEXT *messenger,
-                                       bool create) {
+WEAK int default_vulkan_acquire_context(void *user_context,
+                                        halide_vulkan_memory_allocator **allocator,
+                                        VkInstance *instance,
+                                        VkDevice *device,
+                                        VkPhysicalDevice *physical_device,
+                                        VkQueue *queue,
+                                        uint32_t *queue_family_index,
+                                        VkDebugUtilsMessengerEXT *messenger,
+                                        bool create) {
 #ifdef DEBUG_RUNTIME
     halide_start_clock(user_context);
 #endif
@@ -110,11 +99,57 @@ WEAK int halide_vulkan_acquire_context(void *user_context,
     return halide_error_code_success;
 }
 
-WEAK int halide_vulkan_release_context(void *user_context, VkInstance instance, VkDevice device, VkQueue queue, VkDebugUtilsMessengerEXT messenger) {
+WEAK int default_vulkan_release_context(void *user_context, VkInstance instance, VkDevice device, VkQueue queue, VkDebugUtilsMessengerEXT messenger) {
     halide_mutex_unlock(&thread_lock);
     return halide_error_code_success;
 }
 
+WEAK halide_vulkan_acquire_context_t vulkan_acquire_context_handler =
+    default_vulkan_acquire_context;
+WEAK halide_vulkan_release_context_t vulkan_release_context_handler =
+    default_vulkan_release_context;
+
+}  // namespace Vulkan
+}  // namespace Internal
+}  // namespace Runtime
+}  // namespace Halide
+
+// --------------------------------------------------------------------------
+
+extern "C" {
+
+// --------------------------------------------------------------------------
+
+WEAK int halide_vulkan_acquire_context(void *user_context,
+                                       halide_vulkan_memory_allocator **allocator,
+                                       VkInstance *instance,
+                                       VkDevice *device,
+                                       VkPhysicalDevice *physical_device,
+                                       VkQueue *queue,
+                                       uint32_t *queue_family_index,
+                                       VkDebugUtilsMessengerEXT *messenger,
+                                       bool create) {
+    return vulkan_acquire_context_handler(user_context, allocator, instance, device,
+                                          physical_device, queue, queue_family_index,
+                                          messenger, create);
+}
+
+WEAK int halide_vulkan_release_context(void *user_context, VkInstance instance, VkDevice device, VkQueue queue, VkDebugUtilsMessengerEXT messenger) {
+    return vulkan_release_context_handler(user_context, instance, device, queue, messenger);
+}
+
+WEAK halide_vulkan_acquire_context_t halide_set_vulkan_acquire_context(halide_vulkan_acquire_context_t handler) {
+    halide_vulkan_acquire_context_t result = vulkan_acquire_context_handler;
+    vulkan_acquire_context_handler = handler ? handler : default_vulkan_acquire_context;
+    return result;
+}
+
+WEAK halide_vulkan_release_context_t halide_set_vulkan_release_context(halide_vulkan_release_context_t handler) {
+    halide_vulkan_release_context_t result = vulkan_release_context_handler;
+    vulkan_release_context_handler = handler ? handler : default_vulkan_release_context;
+    return result;
+}
+
 WEAK int halide_vulkan_acquire_memory_allocator(void *user_context,
                                                 halide_vulkan_memory_allocator **allocator,
                                                 VkInstance instance,