Fixes to compile cleanly under MSVC warning-level 4 and /analyze.

lewissbaker · lewissbaker · commit f1349291ef78 · 2017-07-06T22:30:05.000+09:30
- Add [[maybe_unused]] to various parameters/variables.
- Rework a few loops in test-cases to get around some warnings
  about unreachable code.
diff --git a/config.cake b/config.cake
@@ -97,11 +97,14 @@ if cake.system.isWindows() or cake.system.isCygwin():
       compiler.outputMapFile = True
       compiler.outputFullPath = True
       compiler.messageStyle = compiler.MSVS_CLICKABLE
-      compiler.warningLevel = '3'
+      compiler.warningLevel = '4'
       compiler.warningsAsErrors = True
 
       # Enable experimental C++ coroutines via command-line flag.
       compiler.addCppFlag('/await')
+      compiler.addCppFlag('/analyze:WX-')
+      compiler.addCppFlag('/analyze:max_paths')
+      compiler.addCppFlag('512')
 
       # Enable C++17 features like std::optional<>
       compiler.addCppFlag('/std:c++latest')
diff --git a/include/cppcoro/config.hpp b/include/cppcoro/config.hpp
@@ -30,6 +30,12 @@
 # define CPPCORO_COMPILER_GCC 0
 #endif
 
+#if CPPCORO_COMPILER_MSVC
+# define CPPCORO_ASSUME(X) __assume(X)
+#else
+# define CPPCORO_ASSUME(X)
+#endif
+
 /////////////////////////////////////////////////////////////////////////////
 // OS Detection
 
diff --git a/include/cppcoro/lazy_task.hpp b/include/cppcoro/lazy_task.hpp
@@ -45,7 +45,7 @@ namespace cppcoro
 
 					bool await_ready() const noexcept { return false; }
 
-					void await_suspend(std::experimental::coroutine_handle<> coroutine)
+					void await_suspend([[maybe_unused]] std::experimental::coroutine_handle<> coroutine)
 					{
 						m_awaiter.resume();
 					}
diff --git a/include/cppcoro/operation_cancelled.hpp b/include/cppcoro/operation_cancelled.hpp
@@ -9,7 +9,7 @@
 
 namespace cppcoro
 {
-	class operation_cancelled : std::exception
+	class operation_cancelled : public std::exception
 	{
 	public:
 
diff --git a/lib/async_mutex.cpp b/lib/async_mutex.cpp
@@ -14,7 +14,7 @@ cppcoro::async_mutex::async_mutex() noexcept
 
 cppcoro::async_mutex::~async_mutex()
 {
-	auto state = m_state.load(std::memory_order_relaxed);
+	[[maybe_unused]] auto state = m_state.load(std::memory_order_relaxed);
 	assert(state == not_locked || state == locked_no_waiters);
 	assert(m_waiters == nullptr);
 }
diff --git a/lib/cancellation_state.cpp b/lib/cancellation_state.cpp
@@ -5,6 +5,8 @@
 
 #include "cancellation_state.hpp"
 
+#include "cppcoro/config.hpp"
+
 #include <cppcoro/cancellation_registration.hpp>
 
 #include <cassert>
@@ -214,6 +216,11 @@ cppcoro::detail::cancellation_registration_state::add_registration(
 			lastChunk = next;
 		}
 
+		// Work around false-warning raised by MSVC static analysis complaining that
+		// warning C28182: Dereferencing NULL pointer. 'lastChunk' contains the same NULL value as 'chunk' did.
+		// on statement initialising 'elementCount' below.
+		CPPCORO_ASSUME(lastChunk != nullptr);
+
 		if (lastChunk != originalLastChunk)
 		{
 			// Update the cache of last chunk pointer so that subsequent
diff --git a/lib/file_read_operation.cpp b/lib/file_read_operation.cpp
@@ -262,7 +262,7 @@ void cppcoro::file_read_operation::on_operation_completed(
 	detail::win32::io_state* ioState,
 	detail::win32::dword_t errorCode,
 	detail::win32::dword_t numberOfBytesTransferred,
-	detail::win32::ulongptr_t completionKey) noexcept
+	[[maybe_unused]] detail::win32::ulongptr_t completionKey) noexcept
 {
 	auto* operation = static_cast<file_read_operation*>(ioState);
 
diff --git a/lib/file_write_operation.cpp b/lib/file_write_operation.cpp
@@ -262,7 +262,7 @@ void cppcoro::file_write_operation::on_operation_completed(
 	detail::win32::io_state* ioState,
 	detail::win32::dword_t errorCode,
 	detail::win32::dword_t numberOfBytesTransferred,
-	detail::win32::ulongptr_t completionKey) noexcept
+	[[maybe_unused]] detail::win32::ulongptr_t completionKey) noexcept
 {
 	auto* operation = static_cast<file_write_operation*>(ioState);
 
diff --git a/test/async_generator_tests.cpp b/test/async_generator_tests.cpp
@@ -16,10 +16,8 @@ TEST_CASE("default-constructed async_generator is an empty sequence")
 		// Iterating over default-constructed async_generator just
 		// gives an empty sequence.
 		cppcoro::async_generator<int> g;
-		for co_await(int x : g)
-		{
-			CHECK(false);
-		}
+		auto it = co_await g.begin();
+		CHECK(it == g.end());
 	}();
 }
 
diff --git a/test/doctest/doctest.h b/test/doctest/doctest.h
@@ -5284,7 +5284,7 @@ namespace doctest
 				DOCTEST_PRINTF_COLORED(buff, Color::None);
 				DOCTEST_SNPRINTF(buff, DOCTEST_COUNTOF(buff), " | ");
 				DOCTEST_PRINTF_COLORED(buff, Color::None);
-				DOCTEST_SNPRINTF(buff, DOCTEST_COUNTOF(buff), "%6d passed",
+				DOCTEST_SNPRINTF(buff, DOCTEST_COUNTOF(buff), "%6u passed",
 					p->numTestsPassingFilters - p->numFailed);
 				DOCTEST_PRINTF_COLORED(buff,
 					(p->numTestsPassingFilters == 0 || anythingFailed) ?
diff --git a/test/generator_tests.cpp b/test/generator_tests.cpp
@@ -102,11 +102,13 @@ TEST_CASE("destroying generator before completion destructs objects on stack")
 		completed = true;
 	};
 
-	for (auto x : f())
 	{
-		CHECK(x == 1u);
+		auto g = f();
+		auto it = g.begin();
+		auto itEnd = g.end();
+		CHECK(it != itEnd);
+		CHECK(*it == 1u);
 		CHECK(!destructed);
-		break;
 	}
 
 	CHECK(!completed);
diff --git a/test/recursive_generator_tests.cpp b/test/recursive_generator_tests.cpp
@@ -129,11 +129,12 @@ TEST_CASE("destroying generator before completion destructs objects on stack")
 		completed = true;
 	};
 
-	for (auto x : f())
 	{
-		CHECK(x == 1u);
+		auto g = f();
+		auto it = g.begin();
+		auto itEnd = g.end();
+		CHECK(*it == 1u);
 		CHECK(!destructed);
-		break;
 	}
 
 	CHECK(!completed);

Original file line number	Diff line number	Diff line change
`@@ -45,7 +45,7 @@ namespace cppcoro`
`45`	`45`
`46`	`46`	`bool await_ready() const noexcept { return false; }`
`47`	`47`
`48`		`- void await_suspend(std::experimental::coroutine_handle<> coroutine)`
	`48`	`+ void await_suspend([[maybe_unused]] std::experimental::coroutine_handle<> coroutine)`
`49`	`49`	`{`
`50`	`50`	`m_awaiter.resume();`
`51`	`51`	`}`
Original file line number	Diff line number	Diff line change
`@@ -9,7 +9,7 @@`
`9`	`9`
`10`	`10`	`namespace cppcoro`
`11`	`11`	`{`
`12`		`- class operation_cancelled : std::exception`
	`12`	`+ class operation_cancelled : public std::exception`
`13`	`13`	`{`
`14`	`14`	`public:`
`15`	`15`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@ cppcoro::async_mutex::async_mutex() noexcept`
`14`	`14`
`15`	`15`	`cppcoro::async_mutex::~async_mutex()`
`16`	`16`	`{`
`17`		`- auto state = m_state.load(std::memory_order_relaxed);`
	`17`	`+ [[maybe_unused]] auto state = m_state.load(std::memory_order_relaxed);`
`18`	`18`	`assert(state == not_locked \|\| state == locked_no_waiters);`
`19`	`19`	`assert(m_waiters == nullptr);`
`20`	`20`	`}`
Original file line number	Diff line number	Diff line change
`@@ -262,7 +262,7 @@ void cppcoro::file_read_operation::on_operation_completed(`
`262`	`262`	`detail::win32::io_state* ioState,`
`263`	`263`	`detail::win32::dword_t errorCode,`
`264`	`264`	`detail::win32::dword_t numberOfBytesTransferred,`
`265`		`- detail::win32::ulongptr_t completionKey) noexcept`
	`265`	`+ [[maybe_unused]] detail::win32::ulongptr_t completionKey) noexcept`
`266`	`266`	`{`
`267`	`267`	`auto* operation = static_cast<file_read_operation*>(ioState);`
`268`	`268`