Added a test to check how gc works in emscripten.

Test will fail in emscripten and pass in normal environment.

tests/gc/gcemscripten.nim

@@ -0,0 +1,59 @@
+discard """
+  outputsub: "77\n77"
+"""
+
+## Check how GC/Alloc works in Emscripten
+import strutils
+
+type
+  X = ref XObj
+  XObj = object
+    name: string
+    value: int
+when defined(allow_print):
+  const print = true
+else:
+  const print = false
+
+proc myResult3*(i:int):X {.exportc.} =
+  if print: echo "3"
+  new(result)
+  if print: echo "3-2"
+  result.value = i
+
+proc myResult5*(i:int, x:X):X {.exportc.} =
+  if print: echo "5"
+  system.GC_fullCollect()
+  new(result)
+  if print: echo "5-2"
+  result.value = i
+  x.value = i+1
+  if result.value == x.value:
+    echo "This should not happen. Just allocated variable points to parameter"
+
+proc myResult2*(val: string, i: int): X {.exportc.} =
+  if print: echo "2-1"
+  result = myResult3(i)
+  if print: echo "2-2"
+  system.GC_fullCollect()
+  if print: echo "2-3"
+  var t = new(X)
+  if print: echo "2-4"
+  result.name = val
+  if t.name == "qwe":
+    echo "This should not happen. Variable is GC collected and new one on same place are allocated."
+  if print: echo "2-5"
+
+proc myResult4*(val: string, i: int): X {.exportc.} =
+  if print: echo "4-1"
+  result = myResult5(i, X())
+  if print: echo "4-2"
+
+var x = myResult2("qwe", 77)
+echo intToStr(x.value)
+
+var x2 = myResult4("qwe", 77)
+echo intToStr(x2.value)
+
+
+

tests/testament/categories.nim

@@ -121,6 +121,7 @@ proc gcTests(r: var TResults, cat: Category, options: string) =
     testSpec r, makeTest("tests/gc" / filename, options &
                   " -d:release --gc:markAndSweep", cat, actionRun)
 
+  test "gcemscripten"
   test "growobjcrash"
   test "gcbench"
   test "gcleak"