Fix GC heap corruption on ARM. (#27985)

AntonLapounov · web-flow · commit 75d2c46571a5 · 2020-02-13T14:27:12.000-08:00
Port of dotnet/runtime#1389.
diff --git a/src/gc/gc.cpp b/src/gc/gc.cpp
@@ -14980,7 +14980,7 @@ uint8_t* gc_heap::allocate_in_expanded_heap (generation* gen,
 #else // FEATURE_STRUCTALIGN
         if (!((old_loc == 0) || same_large_alignment_p (old_loc, result+pad)))
         {
-            pad += switch_alignment_size (is_plug_padded (old_loc));
+            pad += switch_alignment_size (pad != 0);
             set_node_realigned (old_loc);
             dprintf (3, ("Allocation realignment old_loc: %Ix, new_loc:%Ix",
                          (size_t)old_loc, (size_t)(result+pad)));

Original file line number	Diff line number	Diff line change
`@@ -14980,7 +14980,7 @@ uint8_t* gc_heap::allocate_in_expanded_heap (generation* gen,`
`14980`	`14980`	`#else // FEATURE_STRUCTALIGN`
`14981`	`14981`	`if (!((old_loc == 0) \|\| same_large_alignment_p (old_loc, result+pad)))`
`14982`	`14982`	`{`
`14983`		`- pad += switch_alignment_size (is_plug_padded (old_loc));`
	`14983`	`+ pad += switch_alignment_size (pad != 0);`
`14984`	`14984`	`set_node_realigned (old_loc);`
`14985`	`14985`	`dprintf (3, ("Allocation realignment old_loc: %Ix, new_loc:%Ix",`
`14986`	`14986`	`(size_t)old_loc, (size_t)(result+pad)));`