Add an internal ASSERT macro

This macro has some advantages over the standard library one:
 - It prints the place where the macro was triggered
 - It "references" the condition even in Release to avoid warnings
 - In release, if possible, it gives compiler hints

It is basically is stripped down version of the ASSERT macros I wrote
for the Daemon engine in src/common/Assert.h

This commit also removes the stray "backend" namespaces for common/
code.

src/tests/NXTTest.cpp

@@ -14,13 +14,11 @@
 
 #include "tests/NXTTest.h"
 
+#include "common/Assert.h"
 #include "utils/BackendBinding.h"
 
 #include "GLFW/glfw3.h"
 
-#include <cassert>
-#define ASSERT assert
-
 namespace {
 
     utils::BackendType ParamToBackendType(BackendType type) {
@@ -34,7 +32,7 @@ namespace {
             case VulkanBackend:
                 return utils::BackendType::Vulkan;
             default:
-                ASSERT(false);
+                NXT_ASSERT(false);
                 return utils::BackendType::Null;
         }
     }
@@ -50,7 +48,7 @@ namespace {
             case VulkanBackend:
                 return "Vulkan";
             default:
-                ASSERT(false);
+                NXT_ASSERT(false);
                 return "";
         }
     }
@@ -107,10 +105,10 @@ NXTTest::~NXTTest() {
 
 void NXTTest::SetUp() {
     binding = utils::CreateBinding(ParamToBackendType(GetParam()));
-    ASSERT(binding != nullptr);
+    NXT_ASSERT(binding != nullptr);
 
     GLFWwindow* testWindow = GetWindowForBackend(binding, GetParam());
-    ASSERT(testWindow != nullptr);
+    NXT_ASSERT(testWindow != nullptr);
 
     binding->SetWindow(testWindow);
 
@@ -231,7 +229,7 @@ void NXTTest::MapSlotsSynchronously() {
 
 // static
 void NXTTest::SlotMapReadCallback(nxtBufferMapReadStatus status, const void* data, nxtCallbackUserdata userdata_) {
-    ASSERT(status == NXT_BUFFER_MAP_READ_STATUS_SUCCESS);
+    NXT_ASSERT(status == NXT_BUFFER_MAP_READ_STATUS_SUCCESS);
 
     auto userdata = reinterpret_cast<MapReadUserdata*>(static_cast<uintptr_t>(userdata_));
     userdata->test->readbackSlots[userdata->slot].mappedData = data;
@@ -242,7 +240,7 @@ void NXTTest::SlotMapReadCallback(nxtBufferMapReadStatus status, const void* dat
 
 void NXTTest::ResolveExpectations() {
     for(const auto& expectation : deferredExpectations) {
-        ASSERT(readbackSlots[expectation.readbackSlot].mappedData != nullptr);
+        NXT_ASSERT(readbackSlots[expectation.readbackSlot].mappedData != nullptr);
 
         // Get a pointer to the mapped copy of the data for the expectation.
         const char* data = reinterpret_cast<const char*>(readbackSlots[expectation.readbackSlot].mappedData);
@@ -314,7 +312,7 @@ namespace detail {
 
     template<typename T>
     testing::AssertionResult ExpectEq<T>::Check(const void* data, size_t size) {
-        ASSERT(size == sizeof(T) * expected.size());
+        NXT_ASSERT(size == sizeof(T) * expected.size());
 
         const T* actual = reinterpret_cast<const T*>(data);
         for (size_t i = 0; i < expected.size(); ++i) {

src/tests/unittests/BitSetIteratorTests.cpp

@@ -18,8 +18,6 @@
 
 // This is ANGLE's BitSetIterator_unittests.cpp file.
 
-using namespace backend;
-
 class BitSetIteratorTest : public testing::Test {
     protected:
         std::bitset<40> mStateBits;

src/tests/unittests/MathTests.cpp

@@ -16,8 +16,6 @@
 
 #include "common/Math.h"
 
-using namespace backend;
-
 // Tests for ScanForward
 TEST(Math, ScanForward) {
     // Test extrema

src/tests/unittests/SerialQueueTests.cpp

@@ -16,11 +16,11 @@
 
 #include "common/SerialQueue.h"
 
-using SerialQueue = backend::SerialQueue<int>;
+using TestSerialQueue = SerialQueue<int>;
 
 // A number of basic tests for SerialQueue that are difficult to split from one another
 TEST(SerialQueue, BasicTest) {
-    SerialQueue queue;
+    TestSerialQueue queue;
 
     // Queue starts empty
     ASSERT_TRUE(queue.Empty());
@@ -57,7 +57,7 @@ TEST(SerialQueue, BasicTest) {
 
 // Test enqueuing vectors works
 TEST(SerialQueue, EnqueueVectors) {
-    SerialQueue queue;
+    TestSerialQueue queue;
 
     std::vector<int> vector1 = {1, 2, 3, 4};
     std::vector<int> vector2 = {5, 6, 7, 8};
@@ -78,7 +78,7 @@ TEST(SerialQueue, EnqueueVectors) {
 
 // Test IterateUpTo
 TEST(SerialQueue, IterateUpTo) {
-    SerialQueue queue;
+    TestSerialQueue queue;
 
     std::vector<int> vector1 = {1, 2, 3, 4};
     std::vector<int> vector2 = {5, 6, 7, 8};
@@ -99,7 +99,7 @@ TEST(SerialQueue, IterateUpTo) {
 
 // Test ClearUpTo
 TEST(SerialQueue, ClearUpTo) {
-    SerialQueue queue;
+    TestSerialQueue queue;
 
     std::vector<int> vector1 = {1, 2, 3, 4};
     std::vector<int> vector2 = {5, 6, 7, 8};
@@ -122,7 +122,7 @@ TEST(SerialQueue, ClearUpTo) {
 
 // Test FirstSerial
 TEST(SerialQueue, FirstSerial) {
-    SerialQueue queue;
+    TestSerialQueue queue;
 
     std::vector<int> vector1 = {1, 2, 3, 4};
     std::vector<int> vector2 = {5, 6, 7, 8};