[[ Bug 19873 ]] Ensure MCForeignValue content is 64-bit aligned

runrevmark · runrevmark · commit 062b6f8a08d9 · 2017-06-16T09:29:32.000+01:00
This patch forces the content portion of MCForeignValue structs
to be 64-bit aligned. This ensures that emscripten does not have
to generate 'special' code to access a double which has been
packed into the struct as when it does use the non-aligned
code path, the numbers gain error which cause repeat loops to
behave unexpectedly.
diff --git a/docs/lcb/notes/19873.md b/docs/lcb/notes/19873.md
@@ -0,0 +1 @@
+# Ensure doubles don't get munged in repeat loops in HTML5
diff --git a/libfoundation/src/foundation-private.h b/libfoundation/src/foundation-private.h
@@ -425,7 +425,11 @@ struct __MCCustomValue: public __MCValue
 
 struct __MCForeignValue: public __MCValue
 {
-    MCTypeInfoRef typeinfo;
+    union
+    {
+        MCTypeInfoRef typeinfo;
+        uint64_t _dummy;
+    };
 };
 
 ////////
diff --git a/tests/lcb/vm/repeat-loops.lcb b/tests/lcb/vm/repeat-loops.lcb
@@ -0,0 +1,61 @@
+module __VMTEST.repeat_loops
+
+public handler TestRepeatForUpTo()
+	-- This test ensures that repeat up to loops perform the correct number of
+	-- iterations, motivated by a 'double' issue on emscripten. Rather than
+	-- use numbers to test, we use a string which accumulates a new char for
+	-- each iteration ensuring that the method of testing is entirely distinct
+	-- from what is being tested.
+
+	variable tLoopCount as String
+	variable tCount as Number
+
+	put the empty string into tLoopCount
+	repeat with tCount from 1 up to 12
+		put "X" after tLoopCount
+	end repeat
+	test "from 1 up to 12 gives 12 iterations" when tLoopCount is "XXXXXXXXXXXX"
+
+	put the empty string into tLoopCount
+	repeat with tCount from 1 up to 12 by 2
+		put "X" after tLoopCount
+	end repeat
+	test "from 1 up to 12 by 2 gives 6 iterations" when tLoopCount is "XXXXXX"
+
+	put the empty string into tLoopCount
+	repeat with tCount from 1 up to 12 by 0.5
+		put "X" after tLoopCount
+	end repeat
+	test "from 1 up to 12 by 0.5 gives 24 iterations" when tLoopCount is "XXXXXXXXXXXXXXXXXXXXXXX"
+end handler
+
+public handler TestRepeatForDownTo()
+	-- This test ensures that repeat down to loops perform the correct number of
+	-- iterations, motivated by a 'double' issue on emscripten. Rather than
+	-- use numbers to test, we use a string which accumulates a new char for
+	-- each iteration ensuring that the method of testing is entirely distinct
+	-- from what is being tested.
+
+	variable tLoopCount as String
+	variable tCount as Number
+
+	put the empty string into tLoopCount
+	repeat with tCount from 12 down to 1
+		put "X" after tLoopCount
+	end repeat
+	test "from 12 down to 1 gives 12 iterations" when tLoopCount is "XXXXXXXXXXXX"
+
+	put the empty string into tLoopCount
+	repeat with tCount from 12 down to 1 by -2
+		put "X" after tLoopCount
+	end repeat
+	test "from 12 down to 1 by 2 gives 6 iterations" when tLoopCount is "XXXXXX"
+
+	put the empty string into tLoopCount
+	repeat with tCount from 12 down to 1 by -0.5
+		put "X" after tLoopCount
+	end repeat
+	test "from 12 down to 1 by 0.5 gives 24 iterations" when tLoopCount is "XXXXXXXXXXXXXXXXXXXXXXX"
+end handler
+
+end module

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+# Ensure doubles don't get munged in repeat loops in HTML5`