diff --git a/public/filesystem_passthru.h b/public/filesystem_passthru.h
index 94735f1f..b5c9b19d 100644
--- a/public/filesystem_passthru.h
+++ b/public/filesystem_passthru.h
@@ -115,12 +115,13 @@ public:
 	virtual char			*ReadLine( char *pOutput, int maxChars, FileHandle_t file )							{ return m_pFileSystemPassThru->ReadLine( pOutput, maxChars, file ); }
 	virtual int				FPrintf( FileHandle_t file, char *pFormat, ... ) 
 	{ 
+		char _fmt[] = "%s";
 		char str[8192];
 		va_list marker;
 		va_start( marker, pFormat );
 		_vsnprintf( str, sizeof( str ), pFormat, marker );
 		va_end( marker );
-		return m_pFileSystemPassThru->FPrintf( file, "%s", str );
+		return m_pFileSystemPassThru->FPrintf( file, _fmt, str );
 	}
 	virtual CSysModule 		*LoadModule( const char *pFileName, const char *pPathID, bool bValidatedDllOnly )	{ return m_pFileSystemPassThru->LoadModule( pFileName, pPathID, bValidatedDllOnly ); }
 	virtual void			UnloadModule( CSysModule *pModule )													{ m_pFileSystemPassThru->UnloadModule( pModule ); }
diff --git a/public/tier0/basetypes.h b/public/tier0/basetypes.h
index a30fc515..ef36ebdb 100644
--- a/public/tier0/basetypes.h
+++ b/public/tier0/basetypes.h
@@ -64,6 +64,9 @@ inline T AlignValue( T val, unsigned alignment )
 	( ((number) + ((boundary)-1)) / (boundary) ) * (boundary)
 
 // In case this ever changes
+#if defined M_PI
+#undef M_PI
+#endif
 #define M_PI			3.14159265358979323846
 
 #ifndef min
diff --git a/public/tier0/platform.h b/public/tier0/platform.h
index cc3b6f29..df39adaa 100644
--- a/public/tier0/platform.h
+++ b/public/tier0/platform.h
@@ -21,7 +21,11 @@
 #define NEW_SOFTWARE_LIGHTING
 
 // need this for _alloca
+#if defined __APPLE__
+#include <alloca.h>
+#else
 #include <malloc.h>
+#endif
 #ifdef _MSC_VER
 #include <new.h>
 #elif defined __GNUC__
diff --git a/public/tier0/threadtools.h b/public/tier0/threadtools.h
index a6e806ab..196f8188 100644
--- a/public/tier0/threadtools.h
+++ b/public/tier0/threadtools.h
@@ -1052,6 +1052,9 @@ inline CThreadMutex::CThreadMutex()
 {
 	// enable recursive locks as we need them
 	pthread_mutexattr_init( &m_Attr );
+#if defined __APPLE__
+#define PTHREAD_MUTEX_RECURSIVE_NP PTHREAD_MUTEX_RECURSIVE
+#endif
 	pthread_mutexattr_settype( &m_Attr, PTHREAD_MUTEX_RECURSIVE_NP );
 	pthread_mutex_init( &m_Mutex, &m_Attr );
 }
diff --git a/public/tier1/KeyValues.h b/public/tier1/KeyValues.h
index 69636da5..4f3d04b9 100644
--- a/public/tier1/KeyValues.h
+++ b/public/tier1/KeyValues.h
@@ -147,8 +147,8 @@ public:
 	void SetColor( const char *keyName, Color value);
 
 	// Memory allocation (optimized)
-	void *operator new( unsigned int iAllocSize );
-	void *operator new( unsigned int iAllocSize, int nBlockUse, const char *pFileName, int nLine );
+	void *operator new( size_t iAllocSize );
+	void *operator new( size_t iAllocSize, int nBlockUse, const char *pFileName, int nLine );
 	void operator delete( void *pMem );
 	void operator delete( void *pMem, int nBlockUse, const char *pFileName, int nLine );
 
diff --git a/tier1/KeyValues.cpp b/tier1/KeyValues.cpp
index fea17654..89d22f0b 100644
--- a/tier1/KeyValues.cpp
+++ b/tier1/KeyValues.cpp
@@ -2131,13 +2131,13 @@ bool KeyValues::ReadAsBinary( CUtlBuffer &buffer )
 //-----------------------------------------------------------------------------
 // Purpose: memory allocator
 //-----------------------------------------------------------------------------
-void *KeyValues::operator new( unsigned int iAllocSize )
+void *KeyValues::operator new( size_t iAllocSize )
 {
 	MEM_ALLOC_CREDIT();
 	return KeyValuesSystem()->AllocKeyValuesMemory(iAllocSize);
 }
 
-void *KeyValues::operator new( unsigned int iAllocSize, int nBlockUse, const char *pFileName, int nLine )
+void *KeyValues::operator new( size_t iAllocSize, int nBlockUse, const char *pFileName, int nLine )
 {
 	MemAlloc_PushAllocDbgInfo( pFileName, nLine );
 	void *p = KeyValuesSystem()->AllocKeyValuesMemory(iAllocSize);