[C++ification] Take care of a few warnings and don't use LTO (#3873)

Desktop compilers mis-detect memory allocation size in our bundled
property code if a fortified version of **strncpy**(3) is used (even
though the size calculation is correct).  Use **memcpy**(3) instead.

LTO doesn't appear to be ready for use just yet.  It gives warnings
similar to these:

	jni-wrappers.hh(143,41): warning GD616DC71: argument 1 value ‘18446744073709551615’ exceeds maximum object size 9223372036854775807
	util.cc(75,8): warning GA5933D32: ‘MEM[(struct timing_point *)&partial_time].ns’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Which, even though well-intentioned (and, technically, correct) are
irrelevant in our case and the compiler+linker diagnostics fail to
understand the intention and usage of the code.

Additionally, fix a few instances where type conversion is different
for different platforms/targets.

build-tools/cmake/xa_macros.cmake

@@ -51,14 +51,6 @@ macro(xa_common_prepare)
     fPIC
     )
 
-  # Using flto seems to breaks LLDB debugging as debug symbols are not properly included
-  # thus disable on desktop builds where we care less about its benefits and would rather
-  # keep debuggability
-  if(NOT MINGW AND NOT WIN32 AND NOT APPLE)
-    # -flto leaves a lot of temporary files with mingw builds, turn the optimization off as we don't really need it there
-    set(XA_COMPILER_FLAGS ${XA_COMPILER_FLAGS} flto)
-  endif()
-
   if(CMAKE_BUILD_TYPE STREQUAL Debug)
     set(XA_COMPILER_FLAGS ${XA_COMPILER_FLAGS} ggdb3 fno-omit-frame-pointer O0)
   else()

src/monodroid/jni/android-system.cc

@@ -133,7 +133,7 @@ AndroidSystem::add_system_property (const char *name, const char *value)
 		return;
 
 	p->name = ((char*) p) + sizeof (struct BundledProperty);
-	strncpy (p->name, name, name_len);
+	memcpy (p->name, name, name_len);
 	p->name [name_len] = '\0';
 
 	if (value == nullptr) {
@@ -192,8 +192,8 @@ AndroidSystem::_monodroid__system_property_get (const char *name, char *sp_value
 	//    ../../../jni/android-system.cc(206,10): warning G20816D19: ‘char* strncpy(char*, const char*, size_t)’ specified bound 93 equals destination size [-Wstringop-truncation] [/home/grendel/vc/xamarin/xamarin-android-worktrees/code-quality-improvements/src/monodroid/monodroid.csproj]
 	//    strncpy (sp_value, env_value, sp_value_len);
 	//
-	strncpy (sp_value, env_value, sp_value_len - 1);
-	sp_value[sp_value_len] = '\0';
+	strncpy (sp_value, env_value, sp_value_len - 2);
+	sp_value[sp_value_len - 1] = '\0';
 
 	return static_cast<int>(strlen (sp_value));
 }

src/monodroid/jni/embedded-assemblies-zip.cc

@@ -330,8 +330,7 @@ EmbeddedAssemblies::zip_read_field (uint8_t* buf, size_t buf_len, size_t index,
 		return false;
 	}
 
-	u = static_cast<uint16_t> (buf [index + 1] << 8) |
-		static_cast<uint16_t> (buf [index]);
+	u = static_cast<uint16_t>((buf [index + 1] << 8) | buf [index]);
 
 	return true;
 }

src/monodroid/jni/monodroid-glue.cc

@@ -916,7 +916,7 @@ MonodroidRuntime::init_android_runtime (MonoDomain *domain, JNIEnv *env, jclass
 	init.localRefsAreIndirect   = LocalRefsAreIndirect (env, runtimeClass, init.androidSdkVersion);
 	init.isRunningOnDesktop     = is_running_on_desktop ? 1 : 0;
 	init.brokenExceptionTransitions = application_config.broken_exception_transitions ? 1 : 0;
-	init.packageNamingPolicy    = application_config.package_naming_policy;
+	init.packageNamingPolicy    = static_cast<int>(application_config.package_naming_policy);
 
 	// GC threshold is 90% of the max GREF count
 	init.grefGcThreshold        = static_cast<int>(androidSystem.get_gref_gc_threshold ());

src/monodroid/jni/timing.hh

@@ -17,10 +17,16 @@ namespace xamarin::android
 {
 	struct timing_point
 	{
-		time_t sec;
-		uint64_t ns;
+		time_t sec = 0;
+		uint64_t ns = 0;
 
 		void mark ();
+
+		void reset ()
+		{
+			sec = 0;
+			ns = 0;
+		}
 	};
 
 	struct timing_period
@@ -37,6 +43,12 @@ namespace xamarin::android
 		{
 			end.mark ();
 		}
+
+		void reset ()
+		{
+			start.reset ();
+			end.reset ();
+		}
 	};
 
 	struct timing_diff
@@ -124,7 +136,7 @@ namespace xamarin::android
 
 			std::lock_guard<std::mutex> lock (sequence_lock);
 			if (sequence->dynamic) {
-				memset (sequence, 0, sizeof(*sequence));
+				sequence->period.reset ();
 				delete sequence;
 				return;
 			}