Simpler memset, avoids ICE on VS2013 Update2

chrome/installer/mini_installer/mini_installer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // mini_installer.exe is the first exe that is run when chrome is being
 // installed or upgraded. It is designed to be extremely small (~5KB with no
 // extra resources linked) and it has two main jobs:
 //   1) unpack the resources (possibly decompressing some)
 //   2) run the real installer (setup.exe) with appropriate flags.
 //
@@ skipping 816 matching lines @@
 // simply implement memset.
 //
 // This also avoids having to explicitly set the __sse2_available hack when
 // linking with both the x64 and x86 obj files which is required when not
 // linking with the std C lib in certain instances (including Chromium) with
 // MSVC.  __sse2_available determines whether to use SSE2 intructions with
 // std C lib routines, and is set by MSVC's std C lib implementation normally.
 extern "C" {
 #pragma function(memset)
 void* memset(void* dest, int c, size_t count) {
-  // Simplistic 32-bit memset C implementation which assumes properly aligned
-  // memory; performance hit on memory that isn't properly aligned, but still
-  // better overall then a 8-bit implementation.
-  size_t adjcount = count >> 2;
-  UINT32 fill = (c << 24 | c << 16 | c << 8 | c);
-  UINT32* dest32 = reinterpret_cast<UINT32*>(dest);
-  UINT8* dest8 = reinterpret_cast<UINT8*>(dest);
-
-  // Take care of the ending 0-3 bytes (binary 11 = 3).  The lack of breaks is
-  // deliberate; it falls through for each byte. Think of it a simplified for
-  // loop.
-  switch (count - (adjcount << 2)) {
-    case 3:
-      dest8[count - 3] = c;
-    case 2:
-      dest8[count - 2] = c;
-    case 1:
-      dest8[count - 1] = c;
+  void* start = dest;
+  while (count--) {
+    *reinterpret_cast<char*>(dest) = static_cast<char>(val);

[grt (UTC plus 2), 2014/05/20 23:04:04]

val -> c?

[scottmg, 2014/05/20 23:55:57]

Urgh. :( Thanks.

I also confirm that I can reproduce the ICE before the patch, and that it's
fixed after.

+    dest = reinterpret_cast<char*>(dest) + 1;
   }
-
-  while (adjcount-- > 0)  // Copy the rest, 4 bytes/32 bits at a time
-    *(dest32++) = fill;
-
-  return dest;
-}
+  return start;
 }  // extern "C"