Fix linking issues with dynamic Vulkan functions.

- Ensure Vulkan public symbols are not stripped from the library when
  statically linked to an app that calls all Vulkan functions dynamically.
- Per Vulkan 1.2 spec, support calling vkGetInstanceProcAddr() with a
  null instance, when vkGetInstanceProcAddr itself is the function name.
- Replace uses of strcmp() with mvkStringsAreEqual() to protect against
  null pointers, and provide a direct bool output (unrelated cleanup).

Common/MVKCommonEnvironment.h

@@ -102,8 +102,7 @@ extern "C" {
 #endif
 
 /** Directive to identify public symbols. */
-#define MVK_PUBLIC_SYMBOL        	__attribute__((visibility("default")))
+#define MVK_PUBLIC_SYMBOL    __attribute__((visibility("default"))) __attribute__((used))
-
 
 /** Directive to make a public alias of another symbol. */
 #define MVK_PUBLIC_ALIAS(ALIAS, TARGET)   asm(".globl _" #ALIAS "\n\t_" #ALIAS " = _" #TARGET)

Docs/Whats_New.md

@@ -22,6 +22,10 @@ Released TBD
   `MTLCommandBuffer` is finished using it.
 - Fix memory leak of `MVKFences` and `MVKSemaphores` when 
   a swapchain image is acquired more than it is presented.
+- Ensure Vulkan public symbols are not stripped from the library when 
+  statically linked to an app that calls all Vulkan functions dynamically.
+- Per Vulkan 1.2 spec, support calling `vkGetInstanceProcAddr()` with a 
+  null instance, when `vkGetInstanceProcAddr` itself is the function name.
 
 
 

MoltenVK/MoltenVK/GPUObjects/MVKInstance.mm

@@ -449,7 +449,6 @@ void MVKInstance::initProcAddrs() {
 	ADD_INST_ENTRY_POINT(vkGetPhysicalDeviceProperties);
 	ADD_INST_ENTRY_POINT(vkGetPhysicalDeviceQueueFamilyProperties);
 	ADD_INST_ENTRY_POINT(vkGetPhysicalDeviceMemoryProperties);
-	ADD_INST_ENTRY_POINT(vkGetInstanceProcAddr);
 	ADD_INST_ENTRY_POINT(vkCreateDevice);
 	ADD_INST_ENTRY_POINT(vkEnumerateDeviceExtensionProperties);
 	ADD_INST_ENTRY_POINT(vkEnumerateDeviceLayerProperties);

MoltenVK/MoltenVK/Layers/MVKExtensions.mm

@@ -141,7 +141,7 @@ bool MVKExtensionList::isEnabled(const char* extnName) const {
 	const MVKExtension* extnAry = &extensionArray;
 	for (uint32_t extnIdx = 0; extnIdx < extnCnt; extnIdx++) {
 		const MVKExtension& extn = extnAry[extnIdx];
-		if ( strcmp(extn.pProperties->extensionName, extnName) == 0 ) {
+		if (mvkStringsAreEqual(extn.pProperties->extensionName, extnName)) {
 			return extn.enabled;
 		}
 	}
@@ -153,7 +153,7 @@ void MVKExtensionList::enable(const char* extnName) {
 	MVKExtension* extnAry = &extensionArray;
 	for (uint32_t extnIdx = 0; extnIdx < extnCnt; extnIdx++) {
 		MVKExtension& extn = extnAry[extnIdx];
-		if ( strcmp(extn.pProperties->extensionName, extnName) == 0 ) {
+		if (mvkStringsAreEqual(extn.pProperties->extensionName, extnName)) {
 			extn.enabled = true;
 			return;
 		}

MoltenVK/MoltenVK/Layers/MVKLayers.mm

@@ -65,7 +65,7 @@ MVKLayer* MVKLayerManager::getLayerNamed(const char* pLayerName) {
 	uint32_t layCnt = (uint32_t)_layers.size();
 	for (uint32_t layIdx = 0; layIdx < layCnt; layIdx++) {
 		MVKLayer* pLayer = &_layers[layIdx];
-		if ( strcmp(pLayer->getName(), pLayerName) == 0 ) { return pLayer; }
+		if (mvkStringsAreEqual(pLayer->getName(), pLayerName)) { return pLayer; }
 	}
 	return VK_NULL_HANDLE;
 }

MoltenVK/MoltenVK/Utility/MVKFoundation.h

@@ -549,6 +549,15 @@ bool mvkAreEqual(const T* pV1, const T* pV2, size_t count = 1) {
 	return (pV1 && pV2) ? (memcmp(pV1, pV2, sizeof(T) * count) == 0) : false;
 }
 
+/**
+ * If both pV1 and pV2 are not null, returns whether the contents of the two strings are equal,
+ * otherwise returns false. This functionality is different than the char version of mvkAreEqual(),
+ * which works on individual chars or char arrays, not strings.
+ */
+static inline bool mvkStringsAreEqual(const char* pV1, const char* pV2, size_t count = 1) {
+	return (pV1 && pV2) ? (strcmp(pV1, pV2) == 0) : false;
+}
+
 /**
  * Sets the value referenced by the destination pointer with the value referenced by
  * the source pointer, and returns whether the value was set.

MoltenVK/MoltenVK/Vulkan/vulkan.mm

@@ -284,17 +284,18 @@ MVK_PUBLIC_VULKAN_SYMBOL PFN_vkVoidFunction vkGetInstanceProcAddr(
     VkInstance                                  instance,
     const char*                                 pName) {
 
-	MVKTraceVulkanCallStart();
-
 	// Handle the special platform functions where the instance parameter may be NULL.
 	PFN_vkVoidFunction func = nullptr;
-	if (strcmp(pName, "vkCreateInstance") == 0) {
+	MVKTraceVulkanCallStart();
+	if (mvkStringsAreEqual(pName, "vkGetInstanceProcAddr")) {
+		func = (PFN_vkVoidFunction)vkGetInstanceProcAddr;
+	} else if (mvkStringsAreEqual(pName, "vkCreateInstance")) {
 		func = (PFN_vkVoidFunction)vkCreateInstance;
-	} else if (strcmp(pName, "vkEnumerateInstanceExtensionProperties") == 0) {
+	} else if (mvkStringsAreEqual(pName, "vkEnumerateInstanceExtensionProperties")) {
 		func = (PFN_vkVoidFunction)vkEnumerateInstanceExtensionProperties;
-	} else if (strcmp(pName, "vkEnumerateInstanceLayerProperties") == 0) {
+	} else if (mvkStringsAreEqual(pName, "vkEnumerateInstanceLayerProperties")) {
 		func = (PFN_vkVoidFunction)vkEnumerateInstanceLayerProperties;
-	} else if (strcmp(pName, "vkEnumerateInstanceVersion") == 0) {
+	} else if (mvkStringsAreEqual(pName, "vkEnumerateInstanceVersion")) {
 		func = (PFN_vkVoidFunction)vkEnumerateInstanceVersion;
 	} else if (instance) {
 		MVKInstance* mvkInst = MVKInstance::getMVKInstance(instance);
@@ -3419,9 +3420,9 @@ MVK_PUBLIC_SYMBOL PFN_vkVoidFunction vk_icdGetInstanceProcAddr(
 	MVKTraceVulkanCallStart();
 
 	PFN_vkVoidFunction func = nullptr;
-	if (strcmp(pName, "vk_icdNegotiateLoaderICDInterfaceVersion") == 0) {
+	if (mvkStringsAreEqual(pName, "vk_icdNegotiateLoaderICDInterfaceVersion")) {
 		func = (PFN_vkVoidFunction)vk_icdNegotiateLoaderICDInterfaceVersion;
-	} else if (strcmp(pName, "vk_icdGetPhysicalDeviceProcAddr") == 0) {
+	} else if (mvkStringsAreEqual(pName, "vk_icdGetPhysicalDeviceProcAddr")) {
 		func = (PFN_vkVoidFunction)vk_icdGetPhysicalDeviceProcAddr;
 	} else {
 		func = vkGetInstanceProcAddr(instance, pName);