diff --git a/compiler/vm.nim b/compiler/vm.nim
index 0d53865027..7355e85fe1 100644
--- a/compiler/vm.nim
+++ b/compiler/vm.nim
@@ -495,18 +495,46 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       else: stackTrace(c, tos, pc, errNilAccess)
     of opcAddInt:
       decodeBC(rkInt)
-      regs[ra].intVal = regs[rb].intVal + regs[rc].intVal
+      let
+        bVal = regs[rb].intVal
+        cVal = regs[rc].intVal
+        sum = bVal +% cVal
+      if (sum xor bVal) >= 0 or (sum xor cVal) >= 0:
+        regs[ra].intVal = sum
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcAddImmInt:
       decodeBImm(rkInt)
       #message(c.debug[pc], warnUser, "came here")
       #debug regs[rb].node
-      regs[ra].intVal = regs[rb].intVal + imm
+      let
+        bVal = regs[rb].intVal
+        cVal = imm
+        sum = bVal +% cVal
+      if (sum xor bVal) >= 0 or (sum xor cVal) >= 0:
+        regs[ra].intVal = sum
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcSubInt:
       decodeBC(rkInt)
-      regs[ra].intVal = regs[rb].intVal - regs[rc].intVal
+      let
+        bVal = regs[rb].intVal
+        cVal = regs[rc].intVal
+        diff = bVal -% cVal
+      if (diff xor bVal) >= 0 or (diff xor not cVal) >= 0:
+        regs[ra].intVal = diff
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcSubImmInt:
       decodeBImm(rkInt)
-      regs[ra].intVal = regs[rb].intVal - imm
+      let
+        bVal = regs[rb].intVal
+        cVal = imm
+        diff = bVal -% cVal
+      if (diff xor bVal) >= 0 or (diff xor not cVal) >= 0:
+        regs[ra].intVal = diff
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcLenSeq:
       decodeBImm(rkInt)
       #assert regs[rb].kind == nkBracket
@@ -539,7 +567,18 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       regs[ra].intVal = nimsets.cardSet(regs[rb].node)
     of opcMulInt:
       decodeBC(rkInt)
-      regs[ra].intVal = regs[rb].intVal * regs[rc].intVal
+      let
+        bVal = regs[rb].intVal
+        cVal = regs[rc].intVal
+        product = bVal *% cVal
+        floatProd = toBiggestFloat(bVal) * toBiggestFloat(cVal)
+        resAsFloat = toBiggestFloat(product)
+      if resAsFloat == floatProd:
+        regs[ra].intVal = product
+      elif 32.0 * abs(resAsFloat - floatProd) <= abs(floatProd):
+        regs[ra].intVal = product
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcDivInt:
       decodeBC(rkInt)
       if regs[rc].intVal == 0: stackTrace(c, tos, pc, errConstantDivisionByZero)
@@ -632,7 +671,11 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcUnaryMinusInt:
       decodeB(rkInt)
       assert regs[rb].kind == rkInt
-      regs[ra].intVal = -regs[rb].intVal
+      let val = regs[rb].intVal
+      if val != int64.low:
+        regs[ra].intVal = -val
+      else:
+        stackTrace(c, tos, pc, errOverOrUnderflow)
     of opcUnaryMinusFloat:
       decodeB(rkFloat)
       assert regs[rb].kind == rkFloat
diff --git a/lib/pure/events.nim b/lib/pure/events.nim
index e76b846cf2..5830d9109e 100644
--- a/lib/pure/events.nim
+++ b/lib/pure/events.nim
@@ -68,7 +68,7 @@ proc clearHandlers*(handler: var TEventHandler) =
   ## Clears all of the callbacks from the event handler.
   setLen(handler.handlers, 0)
 
-proc getEventhandler(emitter: var TEventEmitter, event: string): int =
+proc getEventHandler(emitter: var TEventEmitter, event: string): int =
   for k in 0..high(emitter.s):
     if emitter.s[k].name == event: return k
   return -1
@@ -94,8 +94,6 @@ proc emit*(emitter: var TEventEmitter, event: string, args: TEventArgs) =
   var i = getEventHandler(emitter, event)
   if i >= 0:
     emit(emitter, emitter.s[i], args)
-  else:
-    raise newException(EInvalidEvent, "invalid event: " & event)
 
 proc initEventEmitter*(): TEventEmitter =
   ## Creates and returns a new EventEmitter.
diff --git a/lib/wrappers/zip/zlib.nim b/lib/wrappers/zip/zlib.nim
index f505b95a76..cb61783d25 100644
--- a/lib/wrappers/zip/zlib.nim
+++ b/lib/wrappers/zip/zlib.nim
@@ -182,3 +182,129 @@ proc zlibAllocMem*(AppData: Pointer, Items, Size: int): Pointer {.cdecl.} =
 
 proc zlibFreeMem*(AppData, `Block`: Pointer) {.cdecl.} = 
   dealloc(`Block`)
+
+proc uncompress*(sourceBuf: cstring, sourceLen: int): string =
+  ## Given a deflated cstring returns its inflated version.
+  ##
+  ## Passing a nil cstring will crash this proc in release mode and assert in
+  ## debug mode.
+  ##
+  ## Returns nil on problems. Failure is a very loose concept, it could be you
+  ## passing a non deflated string, or it could mean not having enough memory
+  ## for the inflated version.
+  ##
+  ## The uncompression algorithm is based on
+  ## http://stackoverflow.com/questions/17820664 but does ignore some of the
+  ## original signed/unsigned checks, so may fail with big chunks of data
+  ## exceeding the positive size of an int32. The algorithm can deal with
+  ## concatenated deflated values properly.
+  assert (not sourceBuf.isNil)
+
+  var z: TZStream
+  # Initialize input.
+  z.next_in = sourceBuf
+
+  # Input left to decompress.
+  var left = zlib.Uint(sourceLen)
+  if left < 1:
+    # Incomplete gzip stream, or overflow?
+    return
+
+  # Create starting space for output (guess double the input size, will grow if
+  # needed -- in an extreme case, could end up needing more than 1000 times the
+  # input size)
+  var space = zlib.Uint(left shl 1)
+  if space < left:
+    space = left
+
+  var decompressed = newStringOfCap(space)
+
+  # Initialize output.
+  z.next_out = addr(decompressed[0])
+  # Output generated so far.
+  var have = 0
+
+  # Set up for gzip decoding.
+  z.avail_in = 0;
+  var status = inflateInit2(z, (15+16))
+  if status != Z_OK:
+    # Out of memory.
+    return
+
+  # Make sure memory allocated by inflateInit2() is freed eventually.
+  finally: discard inflateEnd(z)
+
+  # Decompress all of self.
+  while true:
+    # Allow for concatenated gzip streams (per RFC 1952).
+    if status == Z_STREAM_END:
+      discard inflateReset(z)
+
+    # Provide input for inflate.
+    if z.avail_in == 0:
+      # This only makes sense in the C version using unsigned values.
+      z.avail_in = left
+      left -= z.avail_in
+
+    # Decompress the available input.
+    while true:
+      # Allocate more output space if none left.
+      if space == have:
+        # Double space, handle overflow.
+        space = space shl 1
+        if space < have:
+          # Space was likely already maxed out.
+          discard inflateEnd(z)
+          return
+
+        # Increase space.
+        decompressed.setLen(space)
+        # Update output pointer (might have moved).
+        z.next_out = addr(decompressed[have])
+
+      # Provide output space for inflate.
+      z.avail_out = zlib.Uint(space - have)
+      have += z.avail_out;
+
+      # Inflate and update the decompressed size.
+      status = inflate(z, Z_SYNC_FLUSH);
+      have -= z.avail_out;
+
+      # Bail out if any errors.
+      if status != Z_OK and status != Z_BUF_ERROR and status != Z_STREAM_END:
+        # Invalid gzip stream.
+        discard inflateEnd(z)
+        return
+
+      # Repeat until all output is generated from provided input (note
+      # that even if z.avail_in is zero, there may still be pending
+      # output -- we're not done until the output buffer isn't filled)
+      if z.avail_out != 0:
+        break
+    # Continue until all input consumed.
+    if left == 0 and z.avail_in == 0:
+      break
+
+  # Verify that the input is a valid gzip stream.
+  if status != Z_STREAM_END:
+    # Incomplete gzip stream.
+    return
+
+  decompressed.setLen(have)
+  swap(result, decompressed)
+
+
+proc inflate*(buffer: var string): bool {.discardable.} =
+  ## Convenience proc which inflates a string containing compressed data.
+  ##
+  ## Passing a nil string will crash this proc in release mode and assert in
+  ## debug mode. It is ok to pass a buffer which doesn't contain deflated data,
+  ## in this case the proc won't modify the buffer.
+  ##
+  ## Returns true if `buffer` was successfully inflated.
+  assert (not buffer.isNil)
+  if buffer.len < 1: return
+  var temp = uncompress(addr(buffer[0]), buffer.len)
+  if not temp.isNil:
+    swap(buffer, temp)
+    result = true
diff --git a/tests/array/tarrayplus.nim b/tests/array/tarrayplus.nim
index 9e08bbb0a1..0ea349f4f4 100644
--- a/tests/array/tarrayplus.nim
+++ b/tests/array/tarrayplus.nim
@@ -1,5 +1,5 @@
 discard """
-  errmsg: "type mismatch: got (array[0..2, float], array[0..1, float])"
+  errormsg: "type mismatch: got (array[0..2, float], array[0..1, float])"
 """
 
 proc `+`*[R, T] (v1, v2: array[R, T]): array[R, T] =
diff --git a/tests/generics/tbadgenericlambda.nim b/tests/generics/tbadgenericlambda.nim
index 38e7f6cd73..2ab8e724db 100644
--- a/tests/generics/tbadgenericlambda.nim
+++ b/tests/generics/tbadgenericlambda.nim
@@ -1,5 +1,5 @@
 discard """
-  errmsg: "nested proc can have generic parameters only when"
+  errormsg: "nested proc can have generic parameters only when"
   line: 6
 """
 
diff --git a/tests/generics/tmetafield.nim b/tests/generics/tmetafield.nim
index 8e7f265494..f2fac8fdd6 100644
--- a/tests/generics/tmetafield.nim
+++ b/tests/generics/tmetafield.nim
@@ -1,8 +1,8 @@
 discard """
   cmd: "nimrod check $# $#"
-  errmsg: "'proc' is not a concrete type"
-  errmsg: "'Foo' is not a concrete type."
-  errmsg: "invalid type: 'TBaseMed'"
+  errormsg: "'proc' is not a concrete type"
+  errormsg: "'Foo' is not a concrete type."
+  errormsg: "invalid type: 'TBaseMed'"
 """
 
 type
diff --git a/tests/showoff/tdrdobbs_examples.nim b/tests/showoff/tdrdobbs_examples.nim
index 0b3d86a05c..8a39990ba5 100644
--- a/tests/showoff/tdrdobbs_examples.nim
+++ b/tests/showoff/tdrdobbs_examples.nim
@@ -1,7 +1,7 @@
 discard """
   output: '''108
 11 -1 1936
-4.0000000000000002e-001
+4.0000000000000002e-01
 true
 truefalse'''
 """
diff --git a/tests/vm/toverflowopcaddimmint.nim b/tests/vm/toverflowopcaddimmint.nim
new file mode 100644
index 0000000000..c36b9ed9b3
--- /dev/null
+++ b/tests/vm/toverflowopcaddimmint.nim
@@ -0,0 +1,11 @@
+discard """
+  errormsg: "over- or underflow"
+"""
+
+static:
+  proc p =
+    var
+      x = int64.high
+    discard x + 1
+    assert false
+  p()
diff --git a/tests/vm/toverflowopcaddint.nim b/tests/vm/toverflowopcaddint.nim
new file mode 100644
index 0000000000..6d96afc78b
--- /dev/null
+++ b/tests/vm/toverflowopcaddint.nim
@@ -0,0 +1,12 @@
+discard """
+  errormsg: "over- or underflow"
+"""
+
+static:
+  proc p =
+    var
+      x = int64.high
+      y = 1
+    discard x + y
+    assert false
+  p()
diff --git a/tests/vm/toverflowopcmulint.nim b/tests/vm/toverflowopcmulint.nim
new file mode 100644
index 0000000000..81b3234bad
--- /dev/null
+++ b/tests/vm/toverflowopcmulint.nim
@@ -0,0 +1,11 @@
+discard """
+  errormsg: "over- or underflow"
+"""
+
+static:
+  proc p =
+    var
+      x = 1 shl 62
+    discard x * 2
+    assert false
+  p()
diff --git a/tests/vm/toverflowopcsubimmint.nim b/tests/vm/toverflowopcsubimmint.nim
new file mode 100644
index 0000000000..09d6f745bc
--- /dev/null
+++ b/tests/vm/toverflowopcsubimmint.nim
@@ -0,0 +1,10 @@
+discard """
+  errormsg: "over- or underflow"
+"""
+
+static:
+  proc p =
+    var x = int64.low
+    discard x - 1
+    assert false
+  p()
diff --git a/tests/vm/toverflowopcsubint.nim b/tests/vm/toverflowopcsubint.nim
new file mode 100644
index 0000000000..8d114f200e
--- /dev/null
+++ b/tests/vm/toverflowopcsubint.nim
@@ -0,0 +1,12 @@
+discard """
+  errormsg: "over- or underflow"
+"""
+
+static:
+  proc p =
+    var
+      x = int64.low
+      y = 1
+    discard x - y
+    assert false
+  p()