nGW build

- add missing functions SignalCodeMovingGC() and MemoryBarrier() 
- avoid pointer conversion/comparison warnings 
- don't attempt to hide symbols with -fvisibility, MinGW doesn't support it 

BUG=http://code.google.com/p/v8/issues/detail?id=949

Patch by Bert Belder <bertbelder@gmail.com>

Review URL: http://codereview.chromium.org/5471001


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5913 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

AUTHORS

@@ -11,6 +11,7 @@ Hewlett-Packard Development Company, LP
 Alexander Botero-Lowry <alexbl@FreeBSD.org>
 Alexandre Vassalotti <avassalotti@gmail.com>
 Andreas Anyuru <andreas.anyuru@gmail.com>
+Bert Belder <bertbelder@gmail.com>
 Burcu Dogan <burcujdogan@gmail.com>
 Craig Schlenter <craig.schlenter@gmail.com>
 Daniel Andersson <kodandersson@gmail.com>

SConstruct

@@ -654,9 +654,18 @@ def GuessToolchain(os):
     return None
 
 
+def GuessVisibility(os, toolchain):
+  if os == 'win32' and toolchain == 'gcc':
+    # MinGW can't do it.
+    return 'default'
+  else:
+    return 'hidden'
+
+
 OS_GUESS = utils.GuessOS()
 TOOLCHAIN_GUESS = GuessToolchain(OS_GUESS)
 ARCH_GUESS = utils.GuessArchitecture()
+VISIBILITY_GUESS = GuessVisibility(OS_GUESS, TOOLCHAIN_GUESS)
 
 
 SIMPLE_OPTIONS = {
@@ -762,8 +771,8 @@ SIMPLE_OPTIONS = {
   },
   'visibility': {
     'values': ['default', 'hidden'],
-    'default': 'hidden',
-    'help': 'shared library symbol visibility'
+    'default': VISIBILITY_GUESS,
+    'help': 'shared library symbol visibility (%s)' % VISIBILITY_GUESS
   },
   'pgo': {
     'values': ['off', 'instrument', 'optimize'],

src/platform-win32.cc

@@ -207,6 +207,12 @@ int strncpy_s(char* strDest, size_t numberOfElements,
   return 0;
 }
 
+
+inline void MemoryBarrier() {
+  int barrier = 0;
+  __asm__ __volatile__("xchgl %%eax,%0 ":"=r" (barrier));
+}
+
 #endif  // __MINGW32__
 
 // Generate a pseudo-random number in the range 0-2^31-1. Usually
@@ -858,13 +864,14 @@ void* OS::Allocate(const size_t requested,
 
   // VirtualAlloc rounds allocated size to page size automatically.
   size_t msize = RoundUp(requested, static_cast<int>(GetPageSize()));
-  intptr_t address = NULL;
+  intptr_t address = 0;
 
   // Windows XP SP2 allows Data Excution Prevention (DEP).
   int prot = is_executable ? PAGE_EXECUTE_READWRITE : PAGE_READWRITE;
 
   // For exectutable pages try and randomize the allocation address
-  if (prot == PAGE_EXECUTE_READWRITE && msize >= Page::kPageSize) {
+  if (prot == PAGE_EXECUTE_READWRITE &&
+      msize >= static_cast<size_t>(Page::kPageSize)) {
     address = (V8::RandomPrivate() << kPageSizeBits)
       | kAllocationRandomAddressMin;
     address &= kAllocationRandomAddressMax;
@@ -874,7 +881,7 @@ void* OS::Allocate(const size_t requested,
                               msize,
                               MEM_COMMIT | MEM_RESERVE,
                               prot);
-  if (mbase == NULL && address != NULL)
+  if (mbase == NULL && address != 0)
     mbase = VirtualAlloc(NULL, msize, MEM_COMMIT | MEM_RESERVE, prot);
 
   if (mbase == NULL) {
@@ -1347,6 +1354,7 @@ int OS::StackWalk(Vector<OS::StackFrame> frames) {
 
 #else  // __MINGW32__
 void OS::LogSharedLibraryAddresses() { }
+void OS::SignalCodeMovingGC() { }
 int OS::StackWalk(Vector<OS::StackFrame> frames) { return 0; }
 #endif  // __MINGW32__