diff --git a/Contrib/BgImage/BgImage.cpp b/Contrib/BgImage/BgImage.cpp
index 51127a8d..00c16aa9 100644
--- a/Contrib/BgImage/BgImage.cpp
+++ b/Contrib/BgImage/BgImage.cpp
@@ -131,7 +131,7 @@ NSISFunc(SetBg) {
 
     hWndImage = CreateWindowEx(
       WS_EX_TOOLWINDOW,
-      (LPTSTR)(DWORD)atomClass,
+      (LPTSTR)(UINT_PTR)atomClass,
       0,
       WS_CLIPSIBLINGS|WS_POPUP,
       0,
@@ -293,7 +293,7 @@ NSISFunc(AddText) {
   lstrcpy(newImg->szText, szTemp);
 
   popstring(szTemp);
-  newImg->hFont = (HFONT)myatoi(szTemp);
+  newImg->hFont = (HFONT) nsishelper_str_to_ptr(szTemp);
   newImg->cTextColor = GetColor();
   
   GetXY(LPPOINT(&newImg->rPos));
diff --git a/Contrib/InstallOptions/InstallerOptions.cpp b/Contrib/InstallOptions/InstallerOptions.cpp
index 7534b057..9918c6e9 100644
--- a/Contrib/InstallOptions/InstallerOptions.cpp
+++ b/Contrib/InstallOptions/InstallerOptions.cpp
@@ -564,7 +564,7 @@ int WINAPI ReadSettings(void) {
     pField->nMaxLength = myGetProfileInt(_T("MaxLen"), 0);
 
     // Text color for LINK control, default is the system default link color
-    pField->hImage = (HANDLE)myGetProfileInt(_T("TxtColor"), GetLinkColor());
+    pField->hImage = (HANDLE)(UINT_PTR) myGetProfileInt(_T("TxtColor"), GetLinkColor());
 
     pField->nControlID = 1200 + nIdx;
     if (pField->nType == FIELD_FILEREQUEST || pField->nType == FIELD_DIRREQUEST)
@@ -788,7 +788,7 @@ INT_PTR CALLBACK cfgDlgProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lPara
       {
         // Get TxtColor unless the user has set another using SetCtlColors
         if (!GetWindowLongPtr(lpdis->hwndItem, GWLP_USERDATA))
-          SetTextColor(lpdis->hDC, (COLORREF) pField->hImage);
+          SetTextColor(lpdis->hDC, (COLORREF)(INT_PTR) pField->hImage);
 
         // Draw the text
         DrawText(lpdis->hDC, pField->pszText, -1, &rc, DT_CENTER | DT_VCENTER | DT_WORDBREAK | (bRTL ? DT_RTLREADING : 0));
@@ -1212,7 +1212,7 @@ int WINAPI createCfgDlg()
       rect.right - rect.left,
       rect.bottom - rect.top,
       hConfigWindow,
-      (HMENU)pField->nControlID,
+      (HMENU)(UINT_PTR) pField->nControlID,
       m_hInstance,
       NULL
     );
diff --git a/Contrib/Library/RegTool/RegTool.c b/Contrib/Library/RegTool/RegTool.c
index f40b6c49..7e4e38ae 100644
--- a/Contrib/Library/RegTool/RegTool.c
+++ b/Contrib/Library/RegTool/RegTool.c
@@ -13,7 +13,7 @@
 void RegFile(TCHAR cmd, TCHAR *file, int x64);
 void RegDll(TCHAR *file);
 void RegTypeLib(TCHAR *file);
-void DeleteFileOnReboot(TCHAR *pszFile);
+BOOL DeleteFileOnReboot(TCHAR *pszFile);
 
 NSIS_ENTRYPOINT_GUINOCRT
 EXTERN_C void NSISWinMainNOCRT()
@@ -367,9 +367,9 @@ void RenameViaWininit(const TCHAR* prevName, const TCHAR* newName)
 }
 #endif
 
-void DeleteFileOnReboot(TCHAR *pszFile)
+BOOL DeleteFileOnReboot(TCHAR *pszFile)
 {
-  BOOL fOk = 0;
+  BOOL fOk = FALSE;
   HMODULE hLib=GetModuleHandle(_T("KERNEL32.dll"));
   if (hLib)
   {
@@ -385,6 +385,8 @@ void DeleteFileOnReboot(TCHAR *pszFile)
   if (!fOk)
   {
     RenameViaWininit(pszFile, NULL);
+    fOk = TRUE; // BUGBUG: We just pretend everything is OK, nobody checks our return value anyway
   }
 #endif
+  return fOk;
 }
diff --git a/Contrib/Makensisw/utils.cpp b/Contrib/Makensisw/utils.cpp
index 2564e86b..10b14d70 100644
--- a/Contrib/Makensisw/utils.cpp
+++ b/Contrib/Makensisw/utils.cpp
@@ -683,8 +683,8 @@ void ShowDocs() {
   path=_tcsrchr(pathf,_T('\\'));
   if(path!=NULL) *path=0;
   lstrcat(pathf,LOCALDOCS);
-  if ((int)ShellExecute(g_sdata.hwnd,_T("open"),pathf,NULL,NULL,SW_SHOWNORMAL)<=32) 
-  ShellExecuteA(g_sdata.hwnd,"open",DOCPATH,NULL,NULL,SW_SHOWNORMAL);
+  if ((int)(INT_PTR) ShellExecute(g_sdata.hwnd,_T("open"),pathf,NULL,NULL,SW_SHOWNORMAL) <= 32) 
+    ShellExecuteA(g_sdata.hwnd,"open",DOCPATH,NULL,NULL,SW_SHOWNORMAL);
 }
 
 TCHAR* BuildSymbols()
diff --git a/Contrib/Math/Source/Math.c b/Contrib/Math/Source/Math.c
index da39dedc..a77762de 100644
--- a/Contrib/Math/Source/Math.c
+++ b/Contrib/Math/Source/Math.c
@@ -11,6 +11,8 @@ extern "C" int _fltused;
 int _fltused = 1;
 #endif
 
+#define EIPtrToInt(pEI) ( (int) (INT_PTR) (pEI) ) // Make GCC (64-bit) happy. BUGBUG64: Somebody should verify that this truncation is OK
+
 ExpressionItem *stack;
 
 int UserVarsCount, UserFuncsCount;
@@ -28,8 +30,8 @@ void PlaceNewItem(TCHAR *&vb, ParseInfo *pi, int precedence)
     PlaceVariable(vb, pi);
     if (pi->item == NULL) return;
 
-    while ((pi->OpsStack) && ((((int) pi->OpsStack->param2) < precedence)
-        || ((((int)pi->OpsStack->param2) == precedence)
+    while ((pi->OpsStack) && (((EIPtrToInt(pi->OpsStack->param2)) < precedence)
+        || (((EIPtrToInt(pi->OpsStack->param2)) == precedence)
             && (precedence != OPERATOR_SET_PRECEDENCE))))
     {
         // second operand for our operator
@@ -300,7 +302,7 @@ void PlaceOp(TCHAR *&vb, int type, int precedence, ParseInfo *pi)
         // uniary pre op
         ExpressionItem *item = AllocItem();
         item->type = type;
-        item->param2 = (EIPARAM) precedence;
+        item->param2 = (EIPARAM) (INT_PTR) precedence;
         item->next = pi->OpsStack;
         pi->OpsStack = item;
     }
@@ -323,7 +325,7 @@ void PlaceOp(TCHAR *&vb, int type, int precedence, ParseInfo *pi)
         } else
         {
             // binary operator
-            item->param2 = (EIPARAM) precedence;
+            item->param2 = (EIPARAM) (INT_PTR) precedence;
             item->next = pi->OpsStack;
             pi->OpsStack = item;
         }
@@ -857,7 +859,7 @@ void SaveResult(ExpressionItem *var, ExpressionItem *result)
         break;
     case ITV_ARRITEM:
         {
-            ExpressionItem *&ei = ((ArrayDesc*)(var->param1))->array[(int)var->param2];
+            ExpressionItem *&ei = ((ArrayDesc*)(var->param1))->array[(UINT_PTR)(var->param2)];
             CleanupItems(ei);
             ei = CopyItem(result);
         }
@@ -880,9 +882,9 @@ void SaveResult(ExpressionItem *var, ExpressionItem *result)
     }
 }
 
-void RunAndGetConst(int from, ExpressionItem* &result, int type)
+void RunAndGetConst(ExpressionItem* from, ExpressionItem* &result, int type)
 {
-    RunTree(*((ExpressionItem**)&(from)), result, type | RTO_NEEDCONST);
+    RunTree(from, result, type | RTO_NEEDCONST);
     ItemToType(result, type);
 }
 
@@ -930,7 +932,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                 case ITV_ARRITEM:
                     {
                         // array item
-                        ExpressionItem *ei = ((ArrayDesc*)(item->param1))->array[(int)item->param2];
+                        ExpressionItem *ei = ((ArrayDesc*)(item->param1))->array[(UINT_PTR)(item->param2)];
                         if (ei)
                             result = CopyItem(ei);
                         else
@@ -1115,7 +1117,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                         int ir = -666;
                         TCHAR *i1 = (item1)?((TCHAR*)item1->param1):(NULL);
                         TCHAR *i2 = (item2)?((TCHAR*)item2->param1):(NULL);
-                       	int sc = (i1 && i2)?(lstrcmp(i1, i2)):((i1)?(1):((i2)?(-1):(0)));
+                        int sc = (i1 && i2)?(lstrcmp(i1, i2)):((i1)?(1):((i2)?(-1):(0)));
 
                     switch (subtype)
                     {
@@ -1176,7 +1178,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                 }
                 while (true)
                 {
-                    RunAndGetConst((int) ifbr, result, ITC_INT);
+                    RunAndGetConst((ifbr), result, ITC_INT);
                     if (ifmode)
                     {
                         // we need then or else branch?
@@ -1260,20 +1262,21 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                 CleanupItems(si); CleanupItems(var);
             } else if (subtype == ITF_TYPE)
             {
-                int newtype = (int) MathFunctions[ioptions].fptr;
+                INT_PTR newtype = (INT_PTR) MathFunctions[ioptions].fptr;
                 if (newtype < ITC_UNKNOWN)
                 {
                     // get as possibly close to ready expression
-                    RunAndGetConst((int)item->param1, result, newtype);
+                    int truncatednewtype = (int) newtype; // BUGBUG64: Make sure this is safe for 64-bit, meaning, can newtype be < INT_MIN?
+                    RunAndGetConst((item->param1), result, truncatednewtype);
                     if (ioptions == ITFT_CARRAY_ID)
                         CopyArray(result);
                 } else if (newtype == FTT_FLOATF)
                 {
                     // float format function
                     ExpressionItem *arg1, *arg2;
-                    RunAndGetConst((int)item->param1, arg1, ITC_FLOAT);
+                    RunAndGetConst((item->param1), arg1, ITC_FLOAT);
                     double value = *((double*)&(arg1->param1));
-                    RunAndGetConst((int)item->param2, arg2, ITC_INT);
+                    RunAndGetConst((item->param2), arg2, ITC_INT);
                     int format = (int) *((__int64*)&(arg2->param1));
 
                     result = AllocItem();
@@ -1331,7 +1334,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
             } else
             {
                 // oops :-o function call :)
-                RunAndGetConst((int)item->param1, result, ITC_FLOAT);
+                RunAndGetConst((item->param1), result, ITC_FLOAT);
                 double &value = *((double*)&(result->param1));
                 if (subtype == ITF_MATH1)
                 {
@@ -1365,7 +1368,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                     {
                         // normal 2-arg math function
                         ExpressionItem *arg2;
-                        RunAndGetConst((int)item->param2, arg2, ITC_FLOAT);
+                        RunAndGetConst((item->param2), arg2, ITC_FLOAT);
                         double value2 = *((double*)&(arg2->param1));
                         value = ((Math2FuncPtr)(MathFunctions[ioptions].fptr))(value, value2);
                         CleanupItems(arg2);
@@ -1388,7 +1391,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                     if ((*((ExpressionItem **) &(item->param2)))->type != IT_EXPRESSION)
                     {
                         // one index - user need a char
-                        RunAndGetConst((int)item->param2, index, ITC_INT);
+                        RunAndGetConst((item->param2), index, ITC_INT);
 
                         int pos = (int) *((__int64*)&(index->param1));
                         if (pos < 0) pos += len; // -index - means from end
@@ -1408,7 +1411,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                         if ((*((ExpressionItem **) &(item->param2)))->param1 == 0)
                             index = AllocItem();
                         else
-                            RunAndGetConst((int)(*((ExpressionItem **) &(item->param2)))->param1, index, ITC_INT);
+                            RunAndGetConst(((*((ExpressionItem **) &(item->param2)))->param1), index, ITC_INT);
                         if ((*((ExpressionItem **) &(item->param2)))->next->param1 == 0)
                         {
                             // if second index is skipped -> -1 (till last char)
@@ -1416,7 +1419,7 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                             *((__int64*)&(index2->param1)) = -1;
                         }
                         else
-                            RunAndGetConst((int)(*((ExpressionItem **) &(item->param2)))->next->param1, index2, ITC_INT);
+                            RunAndGetConst(((*((ExpressionItem **) &(item->param2)))->next->param1), index2, ITC_INT);
 
                         // ok, we've got two indexes
                         int pos1 = (int) *((__int64*)&(index->param1));
@@ -1445,16 +1448,16 @@ void RunTree(ExpressionItem *from, ExpressionItem* &result, int options)
                 } else
                 {
                     // argument is array
-                    RunAndGetConst((int)item->param2, index, ITC_INT);
+                    RunAndGetConst((item->param2), index, ITC_INT);
 
                     // convert array pointer to array item pointer
                     aritem->type = IT_VARIABLE | ITV_ARRITEM;
                     aritem->param2 = (EIPARAM) *((__int64*)&(index->param1));
 
                     ArrayDesc *ad = (ArrayDesc*)aritem->param1;
-                    if (((int)aritem->param2) >= ad->count)
+                    if ((EIPtrToInt(aritem->param2)) >= ad->count)
                     {
-                        ad->count = ((int)aritem->param2)+1;
+                        ad->count = (EIPtrToInt(aritem->param2))+1;
                         while (ad->count > ad->size)
                         {
                             // resize array
diff --git a/Contrib/NSISdl/netinc.h b/Contrib/NSISdl/netinc.h
index 8360ef50..bb8a3893 100644
--- a/Contrib/NSISdl/netinc.h
+++ b/Contrib/NSISdl/netinc.h
@@ -17,8 +17,12 @@
 #define strcasecmp(x,y) stricmp(x,y)
 #define ERRNO (WSAGetLastError())
 #define SET_SOCK_BLOCK(s,block) { unsigned long __i=block?0:1; ioctlsocket(s,FIONBIO,&__i); }
+#ifndef EWOULDBLOCK
 #define EWOULDBLOCK WSAEWOULDBLOCK
+#endif
+#ifndef EINPROGRESS
 #define EINPROGRESS WSAEWOULDBLOCK
+#endif
 #define memset mini_memset
 #define memcpy mini_memcpy
 // Jim Park: For Unicode support, we need to distinguish whether we are working on
diff --git a/Contrib/System/SConscript b/Contrib/System/SConscript
index 676096b0..35cdc524 100644
--- a/Contrib/System/SConscript
+++ b/Contrib/System/SConscript
@@ -29,34 +29,30 @@ Import('BuildPlugin env')
 defs = ['SYSTEM_EXPORTS']
 msvc = 'msvc' in env['TOOLS'] or 'mstoolkit' in env['TOOLS']
 
-if env['TARGET_ARCH'] != 'amd64' or msvc: # BUGBUG: Call-amd64.S is missing GAS macros
-	srcsuff = ''
-	if env['TARGET_ARCH'] != 'x86':
-		srcsuff = '-' + env['TARGET_ARCH']
-		defs += ['SYSTEM_NOCALLBACKS'] # BUGBUG: Remove this when CallBack() is implemented
-		if msvc: # BUGBUG: Remove this when GAS is fixed
-			defs += ['SYSTEM_PARTIALCALLSUPPORT']
-	filename = 'Call' + srcsuff
+srcsuff = ''
+if env['TARGET_ARCH'] != 'x86':
+	srcsuff = '-' + env['TARGET_ARCH']
+	defs += ['SYSTEM_NOCALLBACKS'] # BUGBUG: Remove this when CallBack() is implemented
+	defs += ['SYSTEM_PARTIALCALLSUPPORT']
+filename = 'Call' + srcsuff
 
-	src_ascpp = """
-		#if 0 /* a C style comment */
-		ERROR: assembler-with-cpp required!
-		#else
-		.end
-		#endif
-	"""
-	conf = env.Configure()
-	if conf.TryCompile('END', '.S'):
-		files += ['Source/'+filename+'.S']
-	elif (not msvc) and conf.TryCompile(src_ascpp, '.S'):
-		files += ['Source/'+filename+'CPP.S']
-	elif (not msvc) and conf.TryCompile(src_ascpp, '.sx'):
-		files += ['Source/'+filename+'CPP.sx']
-	else:
-		print 'WARNING: System.dll: unable to find assembler for '+filename+'.S'
-	conf.Finish()
+src_ascpp = """
+	#if 0 /* a C style comment */
+	ERROR: assembler-with-cpp required!
+	#else
+	.end
+	#endif
+"""
+conf = env.Configure()
+if conf.TryCompile('END', '.S'):
+	files += ['Source/'+filename+'.S']
+elif (not msvc) and conf.TryCompile(src_ascpp, '.S'):
+	files += ['Source/'+filename+'CPP.S']
+elif (not msvc) and conf.TryCompile(src_ascpp, '.sx'):
+	files += ['Source/'+filename+'CPP.sx']
 else:
-	print 'WARNING: System.dll: missing Win64 code, dynamic function calls not supported'
+	print 'WARNING: System.dll: unable to find assembler for '+filename+'.S'
+conf.Finish()
 
 BuildPlugin(
 	target,
diff --git a/Contrib/System/Source/Call-amd64.S b/Contrib/System/Source/Call-amd64.S
index 2dbe3806..969be2ab 100644
--- a/Contrib/System/Source/Call-amd64.S
+++ b/Contrib/System/Source/Call-amd64.S
@@ -15,6 +15,9 @@
 ;# MASM:
 ;# ml64.exe /c Call-amd64.S
 ;#
+;# Notes:
+;# * MASM does not accept 0x* constants and GAS does not accept *h constants in Intel mode, must use decimal!
+;#
 
 ; .if 0
 ;# MASM
@@ -34,6 +37,7 @@ IF 0
 ; .else
 ;# GNU
 .intel_syntax noprefix
+.set __GNU__,1
 
 #define IFDEF .ifdef
 #define ELSE  .else
@@ -45,6 +49,15 @@ IF 0
 #define END          .end
 #define EXTERN       .extern
 
+.macro FUNC_DECL name
+.global \name
+.func   \name
+\name:
+.endm
+.macro FUNC_END name
+.endfunc
+.endm
+
 ;# ~GNU
 ENDIF
 
@@ -68,14 +81,18 @@ SECTION_CODE
 
 
 FUNC_DECL CallProc2 ;# rcx=SystemProc* edx=ParamCount
-  mov [rsp+8h], r12
-  mov [rsp+10h], r13
-  mov [rsp+18h], r14
-  ;#mov [rsp+20h], r15
+  mov [rsp+8], r12
+  mov [rsp+16], r13
+  mov [rsp+24], r14
+  ;#mov [rsp+32], r15
 
   ;# The stack is unaligned on function entry. We have to calculate the required 
   ;# stack size for our parameters + maybe 8 padding bytes to end up 16 byte aligned.
+IFDEF __GNU__
+#define pSystemProc r14
+ELSE
   pSystemProc equ r14
+ENDIF
   mov pSystemProc, rcx ;# Save SystemProc*
   ;# Not required since we zero-extend eax: xor rax, rax
   mov r13d, edx ;# Save ParamCount
@@ -84,9 +101,9 @@ FUNC_DECL CallProc2 ;# rcx=SystemProc* edx=ParamCount
   jnz noparamalignpadding
   lea eax, [eax+8] ;# sizeof(params) + 8 will make us 16 byte aligned
 noparamalignpadding:
-  cmp eax, 28h ;# The ABI guarantees shadow space for the 4 register parameters
+  cmp eax, 40 ;# The ABI guarantees shadow space for the 4 register parameters
   ja computedstacksize
-  mov eax, 28h ;# Minimum (4*8) + 8 to align
+  mov eax, 40 ;# Minimum (4*8) + 8 to align
 computedstacksize:
   mov r12d, eax ;# Save stack size (Zero-extended mov)
   sub rsp, r12
@@ -170,10 +187,10 @@ capturegle_done:
   ;# add/lea rsp and pop is valid in the epilog. Unwind might fail on our version?
   add rsp, r12 ;# Restore stack
   ;# Restore nonvolatile registers:
-  mov r12, [rsp+8h]
-  mov r13, [rsp+10h]
-  mov r14, [rsp+18h]
-  ;#mov r15, [rsp+20h]
+  mov r12, [rsp+8]
+  mov r13, [rsp+16]
+  mov r14, [rsp+24]
+  ;#mov r15, [rsp+32]
   ret
 FUNC_END CallProc2
 
diff --git a/Contrib/System/Source/Call-amd64CPP.S b/Contrib/System/Source/Call-amd64CPP.S
new file mode 100644
index 00000000..33d3beec
--- /dev/null
+++ b/Contrib/System/Source/Call-amd64CPP.S
@@ -0,0 +1,8 @@
+#ifdef _MSC_VER
+#error "MSVC is supposed to use the plain .S file!"
+#endif
+#if 0
+ERROR: assembler-with-cpp required!
+#else
+#include "Call-amd64.S"
+#endif
diff --git a/Contrib/System/Source/Call-amd64CPP.sx b/Contrib/System/Source/Call-amd64CPP.sx
new file mode 100644
index 00000000..76734d0c
--- /dev/null
+++ b/Contrib/System/Source/Call-amd64CPP.sx
@@ -0,0 +1,8 @@
+#ifdef _MSC_VER
+#error "MSVC is supposed to use the plain .S file!"
+#endif
+#if 0
+ERROR: assembler-with-cpp required!
+#else
+#include "Call-amd64CPP.S"
+#endif
diff --git a/Contrib/System/Source/System.c b/Contrib/System/Source/System.c
index 452240da..42f94533 100644
--- a/Contrib/System/Source/System.c
+++ b/Contrib/System/Source/System.c
@@ -276,31 +276,8 @@ PLUGINFUNCTION(Get)
 
 #ifdef _WIN64
 /*
-TODO: CallProc/Back not implemeted.
-Fake the behavior of the System plugin for the LoadImage API function so MUI works.
-BUGBUG: MUI is leaking DeleteObject and failing GetClientRect
+BUGBUG: TODO: CallBack support not implemeted!
 */
-#ifndef SYSTEM_PARTIALCALLSUPPORT
-SystemProc* CallProc(SystemProc *proc)
-{
-    INT_PTR ret, *place;
-    LastError = lstrcmp(proc->ProcName, sizeof(TCHAR) > 1 ? _T("LoadImageW") : _T("LoadImageA"));
-    if (!LastError)
-    {
-        ret = (INT_PTR) LoadImage((HINSTANCE)proc->Params[1].Value,
-          (LPCTSTR)proc->Params[2].Value, (UINT)proc->Params[3].Value,
-          (int)proc->Params[4].Value, (int)proc->Params[5].Value,
-          (UINT)proc->Params[6].Value);
-        LastError = GetLastError();
-    }
-    else
-        proc->ProcResult = PR_ERROR, ret = 0;
-    place = (INT_PTR*) proc->Params[0].Value;
-    if (proc->Params[0].Option != -1) place = (INT_PTR*) &(proc->Params[0].Value);
-    if (place) *place = ret;
-    return proc;
-}
-#endif // ~SYSTEM_PARTIALCALLSUPPORT
 SystemProc* CallBack(SystemProc *proc)
 {
     proc->ProcResult = PR_ERROR;
@@ -461,7 +438,7 @@ SystemProc *PrepareProc(BOOL NeedForCall)
     TCHAR *ibuf, *ib, *sbuf, *cbuf, *cb;
     unsigned int UsedTString = 0;
 
-#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) < 4006
+#ifdef __GNUC__
     temp3 = 0; // "warning: 'temp3' may be used uninitialized in this function": temp3 is set to 0 when we start parsing a new parameter
 #endif
 
@@ -692,14 +669,7 @@ SystemProc *PrepareProc(BOOL NeedForCall)
             case _T('0'): case _T('1'): case _T('2'): case _T('3'): case _T('4'):
             case _T('5'): case _T('6'): case _T('7'): case _T('8'): case _T('9'):
                 // Numeric inline
-#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) >= 4006
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wuninitialized" // temp3 is set to 0 when we start parsing a new parameter
-#endif
                 if (temp3 == 0)
-#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) >= 4006
-#pragma GCC diagnostic pop
-#endif
                 {
                     ib--;
                     // It's stupid, I know, but I'm too lazy to do another thing
@@ -768,14 +738,7 @@ SystemProc *PrepareProc(BOOL NeedForCall)
                 if (temp3 == 1)
                     proc->Params[ParamIndex].Output = (int) temp4; // Note: As long as we never assign a pointer to temp4 when parsing a destination the cast to int is OK.
                 // Next parameter is output or something else
-#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) >= 4006
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wuninitialized"
-#endif  
                 temp3++;
-#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) >= 4006
-#pragma GCC diagnostic pop
-#endif
             }
 
             ChangesDone = PCD_DONE;
@@ -1384,7 +1347,7 @@ Returns offset for element Clone of SystemProc structure
 */
 unsigned int GetCloneOffset(void)
 {
-    return (unsigned int)(&(((SystemProc *)0)->Clone));
+    return (unsigned int)(UINT_PTR) (&(((SystemProc *)0)->Clone));
 }
 
 /*
@@ -1392,7 +1355,7 @@ Returns offset for element ProcName of SystemProc structure
 */
 unsigned int GetProcNameOffset(void)
 {
-    return (unsigned int)(&(((SystemProc *)0)->ProcName));
+    return (unsigned int)(UINT_PTR) (&(((SystemProc *)0)->ProcName));
 }
 
 /*
@@ -1400,7 +1363,7 @@ Returns offset for element ArgsSize of SystemProc structure
 */
 unsigned int GetArgsSizeOffset(void)
 {
-    return (unsigned int)(&(((SystemProc *)0)->ArgsSize));
+    return (unsigned int)(UINT_PTR) (&(((SystemProc *)0)->ArgsSize));
 }
 
 /*
@@ -1432,7 +1395,7 @@ Returns offset for element Size of ProcParameter structure
 */
 unsigned int GetSizeOffsetParam(void)
 {
-    return (unsigned int)(&(((ProcParameter *)0)->Size));
+    return (unsigned int)(UINT_PTR) (&(((ProcParameter *)0)->Size));
 }
 
 /*
diff --git a/Contrib/System/Source/System.h b/Contrib/System/Source/System.h
index df53f376..d7a6d9e7 100644
--- a/Contrib/System/Source/System.h
+++ b/Contrib/System/Source/System.h
@@ -155,10 +155,8 @@ extern void ParamsDeAllocate(SystemProc *proc);
 extern void ParamsIn(SystemProc *proc);
 extern void ParamsOut(SystemProc *proc);
 #ifdef SYSTEM_AMD64
-#ifdef SYSTEM_PARTIALCALLSUPPORT
 extern SystemProc* CallProc2(SystemProc *proc, UINT_PTR ParamCount);
 #define CallProc(p) CallProc2((p), (p)->ParamCount) // ParamCount is passed as a parameter so CallProc2 can determine the required stack size without a function call
-#endif
 #else // !SYSTEM_AMD64
 extern SystemProc* CallProc(SystemProc *proc);
 #endif // ~SYSTEM_AMD64
diff --git a/Contrib/UserInfo/UserInfo.c b/Contrib/UserInfo/UserInfo.c
index 609344f4..11274164 100644
--- a/Contrib/UserInfo/UserInfo.c
+++ b/Contrib/UserInfo/UserInfo.c
@@ -71,7 +71,7 @@ TCHAR* GetAccountTypeHelper(BOOL CheckTokenForGroupDeny)
         (CHECKTOKENMEMBERSHIP) GetProcAddress(
           GetModuleHandle(_T("ADVAPI32")), "CheckTokenMembership");
       #else
-        _CheckTokenMembership = CheckTokenMembership;
+        CheckTokenMembership;
       #endif
     
     // Use "old school" membership check?
diff --git a/Contrib/nsDialogs/browse.c b/Contrib/nsDialogs/browse.c
index f5ef584f..0af4dd4f 100644
--- a/Contrib/nsDialogs/browse.c
+++ b/Contrib/nsDialogs/browse.c
@@ -8,9 +8,7 @@
 
 #include "defs.h"
 
-#ifdef _countof
-#define COUNTOF _countof
-#else
+#ifndef COUNTOF
 #define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
 #endif
 
diff --git a/Contrib/nsDialogs/nsDialogs.c b/Contrib/nsDialogs/nsDialogs.c
index 7ed84d57..2243b038 100644
--- a/Contrib/nsDialogs/nsDialogs.c
+++ b/Contrib/nsDialogs/nsDialogs.c
@@ -33,7 +33,7 @@ static COLORREF GetLinkColor()
 
 struct nsControl* NSDFUNC GetControl(HWND hwCtl)
 {
-  unsigned id = (unsigned) GetProp(hwCtl, NSCONTROL_ID_PROP);
+  unsigned id = (unsigned)(UINT_PTR) GetProp(hwCtl, NSCONTROL_ID_PROP);
 
   if (id == 0 || id > g_dialog.controlCount)
   {
diff --git a/Contrib/zip2exe/main.cpp b/Contrib/zip2exe/main.cpp
index 70d37b94..2c6f3bf6 100644
--- a/Contrib/zip2exe/main.cpp
+++ b/Contrib/zip2exe/main.cpp
@@ -7,9 +7,7 @@
 #include <ctype.h>
 #include <commctrl.h>
 
-#ifdef _countof
-#define COUNTOF _countof
-#else
+#ifndef COUNTOF
 #define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
 #endif
 
diff --git a/SCons/Config/gnu b/SCons/Config/gnu
index 74595e45..f6014493 100644
--- a/SCons/Config/gnu
+++ b/SCons/Config/gnu
@@ -4,7 +4,17 @@ Import('defenv')
 
 ### imports
 
-Import('FlagsConfigure')
+Import('FlagsConfigure GetOptionOrEnv')
+
+### HACKS!
+if GetOptionOrEnv('NSIS_SCONS_GNU_ENVPATHHACK'):
+	import os
+	defenv['ENV']['PATH'] = os.getenv('PATH') # Major hack!
+	import_env = ['SystemDrive', 'SystemRoot', 'TEMP', 'TMP', 'PATHEXT']
+	for var in import_env: 
+		if var in os.environ:
+			defenv['ENV'][var] = os.environ.get(var, '')
+	#print defenv.Dump()
 
 ### cross compiling
 
@@ -15,10 +25,11 @@ def cross_env(env):
 ### flags
 
 def entry(x,u):
-	if x == 'NSISWinMainNOCRT':
-		x = '_' + x
-	elif x == 'DllMain':
-		x = '_DllMain@12'
+	if defenv['TARGET_ARCH'] == 'x86':
+		if x == 'NSISWinMainNOCRT':
+			x = '_' + x
+		elif x == 'DllMain':
+			x = '_DllMain@12'
 	return '-Wl,-e%s' % x
 
 defenv['ENTRY_FLAG'] = entry
@@ -203,6 +214,12 @@ conf.Finish()
 # sure the sections will be written in the correct order.
 #
 
+if defenv['TARGET_ARCH'] == 'amd64':
+	stub_env.Append(LINKFLAGS = ['-B pei-x86-64'])
+	stub_uenv.Append(LINKFLAGS = ['-B pei-x86-64']) 
+else:
+	stub_env.Append(LINKFLAGS = ['--oformat pei-i386'])
+	stub_uenv.Append(LINKFLAGS = ['--oformat pei-i386'])
 stub_env.Append(LINKFLAGS = ['-T', File('linker_script').rfile()])
 stub_uenv.Append(LINKFLAGS = ['-T', File('linker_script').rfile()])
 
diff --git a/SCons/Config/linker_script b/SCons/Config/linker_script
index 193e0474..5a8bf450 100644
--- a/SCons/Config/linker_script
+++ b/SCons/Config/linker_script
@@ -1,4 +1,6 @@
-OUTPUT_FORMAT(pei-i386)
+/*
+OUTPUT_FORMAT(pei-i386 VS pei-x86-64) must be set somewhere else
+*/
 SECTIONS
 {
   .text  __image_base__ + __section_alignment__  :
diff --git a/SCons/utils.py b/SCons/utils.py
index 0bf3e540..9528c53b 100644
--- a/SCons/utils.py
+++ b/SCons/utils.py
@@ -118,4 +118,17 @@ def FlagsConfigure(env):
 	"""
 	return env.Configure(custom_tests = { 'CheckCompileFlag' : check_compile_flag, 'CheckLinkFlag': check_link_flag })
 
-Export('AddAvailableLibs AddZLib FlagsConfigure GetAvailableLibs')
+def GetOptionOrEnv(name, defval = None):
+	"""
+	Get option set on scons command line or in os.environ
+	"""
+	import os
+	#if optenv and optenv.has_key(name):
+	#	return optenv[name]
+	if ARGUMENTS.has_key(name):
+		return ARGUMENTS[name]
+	if os.environ.has_key(name):
+		return os.environ[name]
+	return defval
+
+Export('AddAvailableLibs AddZLib FlagsConfigure GetAvailableLibs GetOptionOrEnv')
diff --git a/SConstruct b/SConstruct
index e97a858c..06cf5b2b 100644
--- a/SConstruct
+++ b/SConstruct
@@ -336,7 +336,7 @@ defenv['DISTSUFFIX'] = ''
 if defenv['TARGET_ARCH'] == 'amd64':
 	defenv['DISTSUFFIX'] += '-amd64'
 if defenv.has_key('CODESIGNER'):
-	defenv['DISTSUFFIX'] = '-signed'
+	defenv['DISTSUFFIX'] += '-signed'
 
 defenv.Execute(Delete('$ZIPDISTDIR'))
 defenv.Execute(Delete('$INSTDISTDIR'))
@@ -448,7 +448,7 @@ def DistributeExtras(env, target, examples, docs):
 ######################################################################
 
 if defenv['MSTOOLKIT']:
-	if ARGUMENTS.get('MSVC_USE_SCRIPT', ''):
+	if GetOptionOrEnv('MSVC_USE_SCRIPT', '!') != '!':
 		defenv['MSVC_USE_SCRIPT'] = ARGUMENTS.get('MSVC_USE_SCRIPT')
 	defenv.Tool('mstoolkit', toolpath = [Dir('SCons/Tools').rdir()])
 
diff --git a/Source/Platform.h b/Source/Platform.h
index a6d1df23..09396b51 100644
--- a/Source/Platform.h
+++ b/Source/Platform.h
@@ -139,9 +139,7 @@ typedef DWORDLONG ULONGLONG,*PULONGLONG;
 #endif
 #endif
 
-#ifdef _countof
-#define COUNTOF _countof
-#else
+#ifndef COUNTOF
 #define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
 #endif
 
@@ -1020,22 +1018,22 @@ typedef struct tagVS_FIXEDFILEINFO {
 
 /*
 _tprintf on Windows/MSVCRT treats %s as TCHAR* and on POSIX %s is always char*!
-Always use our NPRI* (NsisPRInt[Narrow|Wide]*) defines in format strings when calling 
+Always use our NPRI* (NsisPRInt*[Narrow|Wide]) defines in format strings when calling 
 functions from tchar.h (Similar to the way <inttypes.h> works)
 
 Example: _tprintf(_T("Hello %") NPRIs _T("\n"), _T("World"));
 */
 #ifdef _WIN32
 #  define NPRIs _T("s")
-#  define NPRINs _T("hs")
-#  define NPRIWs _T("ls") // ws also works, not sure which is most compatible
+#  define NPRIns _T("hs")
+#  define NPRIws _T("ls") // ws also works, not sure which is most compatible
 #  ifndef _WIN64
 #    define NPRIp _T(".8x")
-#    define NPRINp ".8x"
+#    define NPRIpN ".8x"
 #  endif
 #else  // !_WIN32
-#  define NPRINs _T("s")
-#  define NPRIWs _T("ls")
+#  define NPRIns _T("s")
+#  define NPRIws _T("ls")
 #  ifdef _UNICODE
 #    define NPRIs _T("ls")
 #  else // !_UNICODE
@@ -1044,7 +1042,7 @@ Example: _tprintf(_T("Hello %") NPRIs _T("\n"), _T("World"));
 #endif // ~_WIN32
 #ifndef NPRIp
 #  define NPRIp _T("p")
-#  define NPRINp "p"
+#  define NPRIpN "p"
 #endif
 
 #endif // EOF
diff --git a/Source/ResourceEditor.cpp b/Source/ResourceEditor.cpp
index 905c6dee..7c660af2 100644
--- a/Source/ResourceEditor.cpp
+++ b/Source/ResourceEditor.cpp
@@ -849,7 +849,7 @@ void CResourceDirectory::RemoveEntry(int i) {
 }
 
 unsigned int CResourceDirectory::CountEntries() {
-  return BUGBUG64TRUNCATE(unsigned int,m_vEntries.size());
+  return truncate_cast(unsigned int,m_vEntries.size());
 }
 
 // Returns the index of a directory entry with the specified name
diff --git a/Source/build.cpp b/Source/build.cpp
index e9415473..b4402389 100644
--- a/Source/build.cpp
+++ b/Source/build.cpp
@@ -448,7 +448,7 @@ void CEXEBuild::init_shellconstantvalues()
     // see Source\exehead\util.c for implementation details
     // basically, it knows it needs to get folders from the registry when the 0x80 is on
     const char* msg = "Internal compiler error: too many strings added to strings block before adding shell constants!";
-    ERROR_MSG(_T("%") NPRINs, msg);
+    ERROR_MSG(_T("%") NPRIns, msg);
     throw out_of_range(msg);
   }
 
@@ -469,7 +469,7 @@ void CEXEBuild::init_shellconstantvalues()
     || uncf64_def != cf64_def)
   {
     const char* msg = "Internal compiler error: installer's shell constants are different than uninstallers!";
-    ERROR_MSG(_T("%") NPRINs, msg);
+    ERROR_MSG(_T("%") NPRIns, msg);
     throw out_of_range(msg);
   }
 }
@@ -602,7 +602,7 @@ int CEXEBuild::preprocess_string(TCHAR *out, const TCHAR *in, WORD codepage/*=CP
       {
         // starts with a $ but not $$.
         bool bProceced=false;
-        if ( *p )
+        if (*p)
         {
           const TCHAR *pUserVarName = p;
           while (isSimpleChar(*pUserVarName))
@@ -610,10 +610,10 @@ int CEXEBuild::preprocess_string(TCHAR *out, const TCHAR *in, WORD codepage/*=CP
 
           while (pUserVarName > p)
           {
-            if (m_ShellConstants.get(p, BUGBUG64TRUNCATE(int, pUserVarName-p)) >= 0)
+            if (m_ShellConstants.get(p, truncate_cast(int, (size_t)(pUserVarName - p))) >= 0)
               break; // Woops it's a shell constant
 
-            int idxUserVar = m_UserVarNames.get(p, BUGBUG64TRUNCATE(int, pUserVarName-p));
+            int idxUserVar = m_UserVarNames.get(p, truncate_cast(int, (size_t)(pUserVarName - p)));
             if (idxUserVar >= 0)
             {
               // Well, using variables inside string formating doens't mean
@@ -641,7 +641,7 @@ int CEXEBuild::preprocess_string(TCHAR *out, const TCHAR *in, WORD codepage/*=CP
           while (pShellConstName > p)
           {
             // Look for the identifier in the shell constants list of strings.
-            int idxConst = m_ShellConstants.get((TCHAR*)p, BUGBUG64TRUNCATE(int, pShellConstName - p));
+            int idxConst = m_ShellConstants.get((TCHAR*)p, truncate_cast(int, (size_t)(pShellConstName - p)));
 
             // If found...
             if (idxConst >= 0)
@@ -857,6 +857,14 @@ int CEXEBuild::add_db_data(IMMap *mmap) // returns offset
         bufferlen = INT_MAX-st-sizeof(int); //   so maximize compressor room and hope the file compresses well
       db->resize(st + bufferlen + sizeof(int));
 
+#if defined(NSIS_CONFIG_COMPRESSION_SUPPORT) && defined(__GNUC__) && defined(_WIN64) // There is another one of these, remove both when fixed
+  // BUGBUG: zlib is currently broken on 64-bit MinGW
+  if (compressor == &zlib_compressor)
+  {
+    ERROR_MSG(_T("\nError: ZLib is currently broken on this platform!\n"));
+    return -1;
+  }
+#endif
     int n = compressor->Init(build_compress_level, build_compress_dict_size);
     if (n != C_OK)
     {
@@ -1123,8 +1131,7 @@ int CEXEBuild::add_function(const TCHAR *funname)
 
   // ns_func contains all the function names defined.
   int addr=ns_func.add(funname,0);
-  int x;
-  int n=cur_functions->getlen()/sizeof(section);
+  int n=cur_functions->getlen()/sizeof(section), x;
   section *tmp=(section*)cur_functions->get();
   for (x = 0; x < n; x ++)
   {
@@ -2566,6 +2573,15 @@ int CEXEBuild::write_output(void)
 
   RET_UNLESS_OK( check_write_output_errors() );
 
+#if defined(NSIS_CONFIG_COMPRESSION_SUPPORT) && defined(__GNUC__) && defined(_WIN64) // There is another one of these, remove both when fixed
+  // BUGBUG: zlib is currently broken on 64-bit MinGW
+  if (compressor == &zlib_compressor)
+  {
+    ERROR_MSG(_T("\nError: ZLib is currently broken on this platform!\n"));
+    return PS_ERROR;
+  }
+#endif
+
   has_called_write_output=true;
 
 #ifdef NSIS_CONFIG_PLUGIN_SUPPORT
@@ -3198,7 +3214,7 @@ int CEXEBuild::uninstall_generate()
           compressor->Compress(0);
           if (compressor->GetNextOut() - obuf > 0)
           {
-            udata.add(obuf, BUGBUG64TRUNCATE(int, compressor->GetNextOut() - obuf));
+            udata.add(obuf, truncate_cast(int, (size_t)(compressor->GetNextOut() - obuf)));
           }
         }
 
@@ -3215,7 +3231,7 @@ int CEXEBuild::uninstall_generate()
             compressor->SetNextOut(obuf, sizeof(obuf));
             compressor->Compress(0);
             if (compressor->GetNextOut() - obuf > 0)
-              udata.add(obuf, BUGBUG64TRUNCATE(int, compressor->GetNextOut() - obuf));
+              udata.add(obuf, truncate_cast(int, (size_t)(compressor->GetNextOut() - obuf)));
           }
 
           ubuild_datablock.release();
@@ -3229,7 +3245,7 @@ int CEXEBuild::uninstall_generate()
           compressor->SetNextOut(obuf, sizeof(obuf));
           compressor->Compress(C_FINISH);
           if (compressor->GetNextOut() - obuf > 0)
-            udata.add(obuf, BUGBUG64TRUNCATE(int, compressor->GetNextOut() - obuf));
+            udata.add(obuf, truncate_cast(int, (size_t)(compressor->GetNextOut() - obuf)));
           else break;
         }
         compressor->End();
diff --git a/Source/crc32.c b/Source/crc32.c
index 9bf0a620..6abb952c 100644
--- a/Source/crc32.c
+++ b/Source/crc32.c
@@ -19,10 +19,11 @@
 #include "Platform.h"
 #include "crc32.h"
 #include "exehead/config.h"
+
 #ifdef NSIS_CONFIG_CRC_SUPPORT
 
 // this is based on the (slow,small) CRC32 implementation from zlib.
-crc32_t NSISCALL CRC32(crc32_t crc, const unsigned char *buf, unsigned int len)
+crc32_t NSISCALL CRC32(crc32_t crc, const unsigned char *buf, size_t len)
 {
     static crc32_t crc_table[256];
 
diff --git a/Source/crc32.h b/Source/crc32.h
index 706e20ff..9bb506f2 100644
--- a/Source/crc32.h
+++ b/Source/crc32.h
@@ -16,16 +16,17 @@
  * Reviewed for Unicode support by Jim Park -- 08/24/2007
  */
 
-#include "Platform.h"
-
 #ifndef ___CRC32__H___
 #define ___CRC32__H___
 
+#include "Platform.h"
+#include <stddef.h> // size_t
+
 typedef UINT32 crc32_t;
 
 #ifdef __cplusplus
 extern "C"
 #endif
-crc32_t NSISCALL CRC32(crc32_t crc, const unsigned char *buf, unsigned int len);
+crc32_t NSISCALL CRC32(crc32_t crc, const unsigned char *buf, size_t len);
 
 #endif//!___CRC32__H___
diff --git a/Source/exehead/Ui.c b/Source/exehead/Ui.c
index 26375764..618c2558 100644
--- a/Source/exehead/Ui.c
+++ b/Source/exehead/Ui.c
@@ -290,7 +290,7 @@ FORCE_INLINE int NSISCALL ui_doinstall(void)
     if (header->install_reg_key_ptr)
     {
       myRegGetStr(
-        (HKEY)header->install_reg_rootkey,
+        (HKEY)(UINT_PTR)header->install_reg_rootkey,
         GetNSISStringNP(header->install_reg_key_ptr),
         GetNSISStringNP(header->install_reg_value_ptr),
         ps_tmpbuf,
diff --git a/Source/exehead/bgbg.c b/Source/exehead/bgbg.c
index d03e8c3f..c7eac28a 100644
--- a/Source/exehead/bgbg.c
+++ b/Source/exehead/bgbg.c
@@ -77,7 +77,7 @@ LRESULT CALLBACK BG_WndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 
         if (header->bg_textcolor != -1)
         {
-          HFONT newFont = CreateFontIndirect((LOGFONT *) header->blocks[NB_BGFONT].offset);
+          HFONT newFont = CreateFontIndirect((LOGFONT*) header->blocks[NB_BGFONT].offset);
           if (newFont)
           {
             HFONT oldFont;
diff --git a/Source/exehead/exec.c b/Source/exehead/exec.c
index e91a63d0..ed3b4850 100644
--- a/Source/exehead/exec.c
+++ b/Source/exehead/exec.c
@@ -189,10 +189,10 @@ static LONG NSISCALL myRegDeleteKeyEx(HKEY thiskey, LPCTSTR lpSubKey, int onlyif
 static HKEY NSISCALL GetRegRootKey(int hRootKey)
 {
   if (hRootKey)
-    return (HKEY) hRootKey;
+    return (HKEY) (UINT_PTR) hRootKey;
 
   // HKEY_LOCAL_MACHINE - HKEY_CURRENT_USER == 1
-  return (HKEY) ((int) HKEY_CURRENT_USER + g_exec_flags.all_user_var);
+  return (HKEY) ((UINT_PTR) HKEY_CURRENT_USER + g_exec_flags.all_user_var);
 }
 
 static HKEY NSISCALL myRegOpenKey(REGSAM samDesired)
@@ -870,7 +870,7 @@ static int NSISCALL ExecuteEntry(entry *entry_)
         TCHAR *buf2=GetStringFromParm(0x22);
         GetStringFromParm(0x15); // For update_status_text_buf1
         update_status_text_buf1(LANG_EXECSHELL);
-        x=(int)ShellExecute(g_hwnd,buf0[0]?buf0:NULL,buf3,buf2[0]?buf2:NULL,state_output_directory,parm3);
+        x=(int)(INT_PTR)ShellExecute(g_hwnd,buf0[0]?buf0:NULL,buf3,buf2[0]?buf2:NULL,state_output_directory,parm3);
         if (x < 33)
         {
           log_printf5(_T("ExecShell: warning: error (\"%s\": file:\"%s\" params:\"%s\")=%d"),buf0,buf3,buf2,x);
diff --git a/Source/exehead/fileform.c b/Source/exehead/fileform.c
index 9fcb4e9d..2d6e172d 100644
--- a/Source/exehead/fileform.c
+++ b/Source/exehead/fileform.c
@@ -17,6 +17,10 @@
  */
 
 #include "../Platform.h"
+#if defined(__cplusplus) && defined(truncate_cast)
+#undef BUGBUG64TRUNCATE
+#define BUGBUG64TRUNCATE truncate_cast
+#endif
 #include "fileform.h"
 #include "util.h"
 #include "state.h"
@@ -327,7 +331,13 @@ const TCHAR * NSISCALL loadHeaders(int cl_flags)
   // set offsets to real memory offsets rather than installer's header offset
   left = BLOCKS_NUM;
   while (left--)
-    header->blocks[left].offset += (int)data;
+  {
+#ifdef DEBUG
+    if (h.length_of_header < header->blocks[left].offset)
+      return _LANG_GENERIC_ERROR; // Should never happen
+#endif
+    header->blocks[left].offset += BUGBUG64TRUNCATE(UINT, (UINT_PTR) data);
+  }
 
 #ifdef NSIS_COMPRESS_WHOLE
   header->blocks[NB_DATA].offset = dbd_pos;
@@ -398,7 +408,7 @@ int NSISCALL _dodecomp(int offset, HANDLE hFileOut, unsigned char *outbuf, int o
 
         if (err<0) return -4;
 
-        u=BUGBUG64TRUNCATE(int, (char*)g_inflate_stream.next_out - outbuffer);
+        u=BUGBUG64TRUNCATE(int, (size_t)((char*)g_inflate_stream.next_out - outbuffer));
 
         tc=GetTickCount();
         if (g_exec_flags.status_update & 1 && (tc - ltc > 200 || !input_len))
@@ -501,7 +511,7 @@ static int NSISCALL __ensuredata(int amount)
         {
           return -3;
         }
-        r=(DWORD)g_inflate_stream.next_out-(DWORD)_outbuffer;
+        r=BUGBUG64TRUNCATE(DWORD,(UINT_PTR)g_inflate_stream.next_out)-BUGBUG64TRUNCATE(DWORD,(UINT_PTR)_outbuffer);
         if (r)
         {
           if (!WriteFile(dbd_hFile,_outbuffer,r,&t,NULL) || r != t)
diff --git a/Source/exehead/fileform.h b/Source/exehead/fileform.h
index e8bd9962..9f47d52e 100644
--- a/Source/exehead/fileform.h
+++ b/Source/exehead/fileform.h
@@ -258,7 +258,7 @@ typedef struct
 
 // nsis blocks
 struct block_header {
-  int offset;
+  /*UINT_PTR*/ int offset; // BUGBUG: This should probably be UINT_PTR but that currently crashes :(
   int num;
 };
 
@@ -554,10 +554,10 @@ extern int g_flags;
 extern int g_filehdrsize;
 extern int g_is_uninstaller;
 
-#define g_pages ((page*)g_blocks[NB_PAGES].offset)
-#define g_sections ((section*)g_blocks[NB_SECTIONS].offset)
-#define num_sections (g_blocks[NB_SECTIONS].num)
-#define g_entries ((entry*)g_blocks[NB_ENTRIES].offset)
+#define g_pages ( (page*) g_blocks[NB_PAGES].offset )
+#define g_sections ( (section*) g_blocks[NB_SECTIONS].offset )
+#define num_sections ( g_blocks[NB_SECTIONS].num )
+#define g_entries ( (entry*) g_blocks[NB_ENTRIES].offset )
 #endif
 
 #endif //_FILEFORM_H_
diff --git a/Source/exehead/util.c b/Source/exehead/util.c
index b9bf86e7..437a4ebf 100644
--- a/Source/exehead/util.c
+++ b/Source/exehead/util.c
@@ -567,7 +567,9 @@ void RenameViaWininit(const TCHAR* prevName, const TCHAR* newName)
  */
 void NSISCALL MoveFileOnReboot(LPCTSTR pszExisting, LPCTSTR pszNew)
 {
-  BOOL fOk = 0;
+#ifndef _WIN64 // Shut up GCC unused warning
+  BOOL fOk = FALSE;
+#endif
   typedef BOOL (WINAPI *mfea_t)(LPCTSTR lpExistingFileName,LPCTSTR lpNewFileName,DWORD dwFlags);
   mfea_t mfea;
   #ifdef _WIN64
@@ -577,7 +579,10 @@ void NSISCALL MoveFileOnReboot(LPCTSTR pszExisting, LPCTSTR pszNew)
   if (mfea)
   #endif
   {
-    fOk=mfea(pszExisting, pszNew, MOVEFILE_DELAY_UNTIL_REBOOT|MOVEFILE_REPLACE_EXISTING);
+#ifndef _WIN64 // Shut up GCC unused warning
+    fOk=
+#endif
+      mfea(pszExisting, pszNew, MOVEFILE_DELAY_UNTIL_REBOOT|MOVEFILE_REPLACE_EXISTING);
   }
 #ifndef _WIN64
   if (!fOk)
diff --git a/Source/growbuf.cpp b/Source/growbuf.cpp
index 76400d82..b2edb50c 100644
--- a/Source/growbuf.cpp
+++ b/Source/growbuf.cpp
@@ -30,36 +30,37 @@
 using namespace std;
 
 // Default constructor
-GrowBuf::GrowBuf() { m_alloc=m_used=m_zero=0; m_s=NULL; m_bs=32768; }
+GrowBuf::GrowBuf() { m_alloc=m_used=0, m_zero=false, m_s=NULL, m_bs=32768; }
 
 // Destructor
 GrowBuf::~GrowBuf() { free(m_s); }
 
-void GrowBuf::set_zeroing(int zero) { m_zero=zero; }
+void GrowBuf::set_zeroing(bool zero) { m_zero=zero; }
 
-int GrowBuf::add(const void *data, int len)
+GrowBuf::size_type GrowBuf::add(const void *data, GrowBuf::size_type len)
 {
-  if (len<=0) return 0;
+  if (len<=0) return 0; // BUGBUG: Why is this returning 0? It should return m_used?
   resize(m_used+len);
   memcpy((BYTE*)m_s+m_used-len,data,len);
   return m_used-len;
 }
 
-void GrowBuf::resize(int newlen)
+void GrowBuf::resize(GrowBuf::size_type newlen)
 {
-  int os=m_alloc;  // old size
-  int ou=m_used;   // old used
+  const size_type orgalloc=m_alloc;
+  const size_type orgused=m_used;
+
   m_used=newlen;
   if (newlen > m_alloc)
   {
-    void *n;
+    void *newstor;
 
     // Jim Park: Not sure why we don't just add m_bs.  Multiplying by 2
     // makes m_bs meaningless after a few resizes.  So TinyGrowBuf
     // isn't very tiny.
     m_alloc = newlen*2 + m_bs;
-    n = realloc(m_s, m_alloc);
-    if (!n)
+    newstor = realloc(m_s, m_alloc);
+    if (!newstor)
     {
       extern int g_display_errors;
       if (g_display_errors)
@@ -67,8 +68,8 @@ void GrowBuf::resize(int newlen)
         PrintColorFmtMsg_ERR(_T("\nack! realloc(%d) failed, trying malloc(%d)!\n"),m_alloc,newlen);
       }
       m_alloc=newlen; // try to malloc the minimum needed
-      n=malloc(m_alloc);
-      if (!n)
+      newstor=malloc(m_alloc);
+      if (!newstor)
       {
         extern void quit();
         if (g_display_errors)
@@ -77,15 +78,15 @@ void GrowBuf::resize(int newlen)
         }
         quit();
       }
-      memcpy(n,m_s,min(newlen,os));
+      memcpy(newstor,m_s,min(newlen,orgalloc));
       free(m_s);
     }
-    m_s=n;
+    m_s=newstor;
   }
 
   // Zero out the new buffer area
-  if (m_zero && m_used > ou)
-    memset((BYTE*)m_s + ou, 0, m_used - ou);
+  if (m_zero && m_used > orgused)
+    memset((BYTE*)m_s + orgused, 0, m_used - orgused);
 
   if (!m_used && m_alloc > 2*m_bs) // only free if you resize to 0 and we're > 64k or
                                    // 2K in the case of TinyGrowBuf
@@ -96,7 +97,7 @@ void GrowBuf::resize(int newlen)
   }
 }
 
-int GrowBuf::getlen() const { return m_used; }
+GrowBuf::size_type GrowBuf::getlen() const { return m_used; }
 void *GrowBuf::get() const { return m_s; }
 
 void GrowBuf::swap(GrowBuf&other)
diff --git a/Source/growbuf.h b/Source/growbuf.h
index bc0d2297..2106dfe1 100644
--- a/Source/growbuf.h
+++ b/Source/growbuf.h
@@ -26,6 +26,7 @@
 class IGrowBuf
 {
   public:
+    typedef int size_type; // Hopefully we can change this at some point
     virtual ~IGrowBuf() {}
 
     /**
@@ -34,19 +35,19 @@ class IGrowBuf
      * @param len Size of the data in bytes.
      * @return the previous logical size in bytes before the addition.
      */
-    virtual int add(const void *data, int len)=0;
+    virtual size_type add(const void *data, size_type len)=0;
 
     /**
      * Resizes the buffer to hold the number of bytes specified.
      * @param newlen the desired logical size of the buffer.
      */
-    virtual void resize(int newlen)=0;
+    virtual void resize(size_type newlen)=0;
 
     /**
      * Get the length of the logical buffer in bytes.
      * @return the length in bytes
      */
-    virtual int getlen() const=0;
+    virtual size_type getlen() const=0;
 
     /**
      * Get the buffer itself.
@@ -72,7 +73,7 @@ class GrowBuf : public IGrowBuf
      * Set whether to zero out buffer
      * @param zero A boolean value.
      */
-    void set_zeroing(int zero);
+    void set_zeroing(bool zero);
 
     /**
      * Add data to the buffer.
@@ -80,22 +81,21 @@ class GrowBuf : public IGrowBuf
      * @param len Size of the data in bytes.
      * @return the previous logical size in bytes before the addition.
      */
-    int add(const void *data, int len);
+    size_type add(const void *data, size_type len);
 
     /**
      * Resizes the buffer to hold the number of bytes specified.
+     * Setting the newlen to 0 will cause the buffer to be at most
+     * 2*m_bs bytes long.  (It will free the buffer if > 2*m_bs.)
      * @param newlen the desired logical size of the buffer.
      */
-    void resize(int newlen);
+    void resize(size_type newlen);
 
     /**
      * Get the length of the logical buffer in bytes.
-     * Setting the newlen to 0 will cause the buffer to be at most
-     * 2*m_bs bytes long.  (It will free the buffer if > 2*m_bs.)
-     *
      * @return the length in bytes
      */
-    int getlen() const;
+    size_type getlen() const;
 
     /**
      * Get the buffer itself.
@@ -107,12 +107,12 @@ class GrowBuf : public IGrowBuf
 
   private:
     void *m_s;    /* the storage buffer */
-    int m_alloc;  /* allocated bytes */
-    int m_used;   /* how many bytes of the buffer is used? */
-    int m_zero;   /* should storage be zeroed out? */
+    size_type m_alloc;  /* allocated bytes */
+    size_type m_used;   /* how many bytes of the buffer is used? */
+    bool m_zero;   /* should storage be zeroed out? */
 
   protected:
-    int m_bs;     // byte-size to grow by
+    unsigned short m_bs;     // byte-size to grow by
 };
 
 /**
diff --git a/Source/icon.cpp b/Source/icon.cpp
index 834d2269..40cdc409 100644
--- a/Source/icon.cpp
+++ b/Source/icon.cpp
@@ -228,7 +228,7 @@ static IconPairs get_icon_order(IconGroup icon1, IconGroup icon2)
       FIX_ENDIAN_INT32(sorted_icons1[i].meta.dwRawSize),
       FIX_ENDIAN_INT32(sorted_icons2[i].meta.dwRawSize)
     );
-    pair.size_index = BUGBUG64TRUNCATE(unsigned int,i);
+    pair.size_index = truncate_cast(unsigned int,i);
 
     result.push_back(pair);
   }
@@ -242,7 +242,7 @@ static IconPairs get_icon_order(IconGroup icon1, IconGroup icon2)
       pair.index1 = sorted_icons1[i].index;
       pair.index2 = 0xffff;
       pair.size = FIX_ENDIAN_INT32(sorted_icons1[i].meta.dwRawSize);
-      pair.size_index = BUGBUG64TRUNCATE(unsigned int,i);
+      pair.size_index = truncate_cast(unsigned int,i);
     }
 
     if (i < sorted_icons2.size())
@@ -250,7 +250,7 @@ static IconPairs get_icon_order(IconGroup icon1, IconGroup icon2)
       pair.index2 = sorted_icons2[i].index;
       pair.index1 = 0xffff;
       pair.size = FIX_ENDIAN_INT32(sorted_icons2[i].meta.dwRawSize);
-      pair.size_index = BUGBUG64TRUNCATE(unsigned int,i);
+      pair.size_index = truncate_cast(unsigned int,i);
     }
 
     result.push_back(pair);
diff --git a/Source/makenssi.cpp b/Source/makenssi.cpp
index 4f8367b6..33c23f7b 100644
--- a/Source/makenssi.cpp
+++ b/Source/makenssi.cpp
@@ -118,8 +118,11 @@ static void init_signals(HWND notify_hwnd)
 #ifdef _WIN32
   DWORD id;
   HANDLE hThread = CreateThread(NULL, 0, sigint_event_msg_handler, (LPVOID)notify_hwnd, 0, &id);
-  SetThreadPriority(hThread, THREAD_PRIORITY_HIGHEST);
-  if (hThread) CloseHandle(hThread);
+  if (hThread)
+  {
+    SetThreadPriority(hThread, THREAD_PRIORITY_HIGHEST);
+    CloseHandle(hThread);
+  }
 #endif
 }
 
@@ -326,7 +329,7 @@ static inline int makensismain(int argc, TCHAR **argv)
     {
       initialparsefail=!HasReqParam(argv,++argpos,argc,true);
       if (initialparsefail) break;
-      hostnotifyhandle=(HWND)_ttol(argv[argpos]);
+      hostnotifyhandle=(HWND)(INT_PTR) _ttol(argv[argpos]); // MSDN says we should sign extend HWNDs: msdn.microsoft.com/en-us/library/aa384203
 #ifdef _WIN32
       if (!IsWindow(hostnotifyhandle)) hostnotifyhandle=0;
 #endif
@@ -394,7 +397,7 @@ static inline int makensismain(int argc, TCHAR **argv)
     // The host can override the output format if they want to
     LPARAM lp=MAKELONG(outputenc.GetCodepage(),outputbom);
     LRESULT mr=SendMessage(hostnotifyhandle,MakensisAPI::QUERYHOST,MakensisAPI::QH_OUTPUTCHARSET,lp);
-    if (mr) outputenc.SetCodepage((WORD)--mr), outputbom = -1;
+    if (mr) outputenc.SetCodepage((WORD)(--mr)), outputbom = -1;
   }
 
   if (!WinStdIO_OStreamInit(g_osdata_stdout,g_output,outputenc.GetCodepage(),outputbom))
diff --git a/Source/script.cpp b/Source/script.cpp
index 618288ff..1ead1627 100644
--- a/Source/script.cpp
+++ b/Source/script.cpp
@@ -52,6 +52,8 @@ using namespace std;
 
 #define MAX_INCLUDEDEPTH 10
 
+#define REGROOTKEYTOINT(hk) ( (INT) (((INT_PTR)(hk)) & 0xffffffff) ) // Masking off non-existing top bits to make GCC happy
+
 static UINT read_line_helper(NStreamLineReader&lr, TCHAR*buf, UINT cch)
 {
   // Helper function for reading lines from text files. buf MUST be valid and cch MUST be > 1!
@@ -662,7 +664,7 @@ void CEXEBuild::ps_addtoline(const TCHAR *str, GrowBuf &linedata, StringList &hi
 
     if (t-in > 1) // handle multibyte chars (no escape)
     {
-      linedata.add((void*)in,BUGBUG64TRUNCATE(int,(t-in)*sizeof(TCHAR)));
+      linedata.add((void*)in,truncate_cast(int, (size_t)((t-in)*sizeof(TCHAR))));
       in=t;
       continue;
     }
@@ -1213,7 +1215,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         TCHAR *mbufb=(TCHAR*)m_macros.get();
         const size_t mcb=((mend)-mbeg)*sizeof(TCHAR), mbufcb=m_macros.getlen();
         memmove(mbeg,mend,mbufcb-(((mbeg-mbufb)*sizeof(TCHAR))+mcb));
-        m_macros.resize(BUGBUG64TRUNCATE(int,mbufcb-mcb));
+        m_macros.resize(truncate_cast(int,(size_t)(mbufcb-mcb)));
         SCRIPT_MSG(_T("!macroundef: %") NPRIs _T("\n"),mname);
       }
     return PS_OK;
@@ -2293,7 +2295,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         int k=line.gettoken_enum(1,rootkeys[0]);
         if (k == -1) k=line.gettoken_enum(1,rootkeys[1]);
         if (k == -1) PRINTHELP()
-        build_header.install_reg_rootkey=(INT)rootkey_tab[k];
+        build_header.install_reg_rootkey=REGROOTKEYTOINT(rootkey_tab[k]);
         if (!build_header.install_reg_rootkey) PRINTHELP() // SHCTX is invalid here
         build_header.install_reg_key_ptr = add_string(line.gettoken_str(2),0);
         if (line.gettoken_str(2)[0] == _T('\\'))
@@ -5339,7 +5341,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         int k=line.gettoken_enum(2,rootkeys[0]);
         if (k == -1) k=line.gettoken_enum(2,rootkeys[1]);
         if (ent.offsets[0] == -1 || k == -1) PRINTHELP()
-        ent.offsets[1]=(INT)rootkey_tab[k];
+        ent.offsets[1]=REGROOTKEYTOINT(rootkey_tab[k]);
         ent.offsets[2]=add_string(line.gettoken_str(3));
         ent.offsets[3]=add_string(line.gettoken_str(4));
         if (which_token == TOK_READREGDWORD) ent.offsets[4]=1;
@@ -5371,7 +5373,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         if (k == -1) k=line.gettoken_enum(a,rootkeys[1]);
         if (k == -1) PRINTHELP()
         ent.which=EW_DELREG;
-        ent.offsets[1]=(INT)rootkey_tab[k];
+        ent.offsets[1]=REGROOTKEYTOINT(rootkey_tab[k]);
         ent.offsets[2]=add_string(line.gettoken_str(a+1));
         ent.offsets[3]=(which_token==TOK_DELETEREGKEY)?0:add_string(line.gettoken_str(a+2));
         if (line.gettoken_str(a+1)[0] == _T('\\'))
@@ -5391,7 +5393,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         if (k == -1) k=line.gettoken_enum(1,rootkeys[1]);
         if (k == -1) PRINTHELP()
         ent.which=EW_WRITEREG;
-        ent.offsets[0]=(INT)rootkey_tab[k];
+        ent.offsets[0]=REGROOTKEYTOINT(rootkey_tab[k]);
         ent.offsets[1]=add_string(line.gettoken_str(2));
         if (line.gettoken_str(2)[0] == _T('\\'))
           warning_fl(_T("%") NPRIs _T(": registry path name begins with \'\\\', may cause problems"),line.gettoken_str(0));
@@ -5458,7 +5460,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
         int k=line.gettoken_enum(2,rootkeys[0]);
         if (k == -1) k=line.gettoken_enum(2,rootkeys[1]);
         if (ent.offsets[0] == -1 || k == -1) PRINTHELP()
-        ent.offsets[1]=(INT)rootkey_tab[k];
+        ent.offsets[1]=REGROOTKEYTOINT(rootkey_tab[k]);
         ent.offsets[2]=add_string(line.gettoken_str(3));
         ent.offsets[3]=add_string(line.gettoken_str(4));
         ent.offsets[4]=which_token == TOK_ENUMREGKEY;
diff --git a/Source/strlist.cpp b/Source/strlist.cpp
index e0469731..48456ba5 100644
--- a/Source/strlist.cpp
+++ b/Source/strlist.cpp
@@ -124,7 +124,7 @@ unsigned int ExeHeadStringList::find(const void *ptr, unsigned int cchF, WORD co
 #ifndef NDEBUG
     if (!cbMB)
     {
-      const TCHAR *fmt = _T("Unable to convert%")NPRINs _T(" string \"%")NPRIs _T("\" to codepage %u\n");
+      const TCHAR *fmt = _T("Unable to convert%")NPRIns _T(" string \"%")NPRIs _T("\" to codepage %u\n");
       PrintColorFmtMsg_ERR(fmt,(processed ? " processed" : ""),find,codepage);
     }
 #endif
@@ -160,7 +160,8 @@ unsigned int ExeHeadStringList::find(const void *ptr, unsigned int cchF, WORD co
     else 
       delete[] bufMB;
   }
-  return BUGBUG64TRUNCATE(unsigned int, retval);
+  // -1 is a valid magic return value but we must avoid the truncation check in truncate_cast
+  return retval != (size_t)(-1) ? truncate_cast(unsigned int,retval) : (unsigned int) retval;
 }
 
 int ExeHeadStringList::add(const TCHAR *str, WORD codepage, bool processed)
@@ -203,7 +204,7 @@ int StringList::add(const TCHAR *str, int case_sensitive)
 {
   int a=find(str,case_sensitive);
   if (a >= 0 && case_sensitive!=-1) return a;
-  return m_gr.add(str,BUGBUG64TRUNCATE(int, (_tcslen(str)+1)*sizeof(TCHAR)))/sizeof(TCHAR);
+  return m_gr.add(str,truncate_cast(int,(_tcslen(str)+1)*sizeof(TCHAR)))/sizeof(TCHAR);
 }
 
 // use 2 for case sensitive end-of-string matches too
@@ -233,9 +234,9 @@ int StringList::find(const TCHAR *str, int case_sensitive, int *idx/*=NULL*/) co
         str_slen < offs_slen &&  // check for end of string
         !_tcscmp(s + offs + offs_slen - str_slen,str))
     {
-      return BUGBUG64TRUNCATE(int, offs + offs_slen - str_slen);
+      return truncate_cast(int,offs + offs_slen - str_slen);
     }
-    offs += BUGBUG64TRUNCATE(int, offs_slen + 1);
+    offs += truncate_cast(int,offs_slen + 1);
 
     if (idx) (*idx)++;
   }
@@ -316,7 +317,7 @@ int DefineList::addn(const TCHAR *name, size_t maxvallen, const TCHAR *value)
     extern void quit();
     if (g_display_errors)
     {
-      PrintColorFmtMsg_ERR(_T("\nInternal compiler error #12345: DefineList malloc(%lu) failed.\n"), BUGBUG64TRUNCATE(unsigned long,cbVal));
+      PrintColorFmtMsg_ERR(_T("\nInternal compiler error #12345: DefineList malloc(%lu) failed.\n"), truncate_cast(unsigned long,cbVal));
     }
     quit();
   }
diff --git a/Source/util.cpp b/Source/util.cpp
index 461b27a3..8e54da36 100644
--- a/Source/util.cpp
+++ b/Source/util.cpp
@@ -456,8 +456,8 @@ void create_code_page_string(TCHAR *buf, size_t len, UINT code_page)
   if (!g_nrt_iconv_narrowloc) NSISRT_Initialize(); // For winchar.cpp unit test
   switch(code_page)
   {
-  case CP_ACP:   _sntprintf(buf, len, _T("%") NPRINs, iconv_ACP); return;
-  case CP_OEMCP: _sntprintf(buf, len, _T("%") NPRINs, iconv_OEM); return;
+  case CP_ACP:   _sntprintf(buf, len, _T("%") NPRIns, iconv_ACP); return;
+  case CP_OEMCP: _sntprintf(buf, len, _T("%") NPRIns, iconv_OEM); return;
   case CP_UTF8:  _sntprintf(buf, len, _T("UTF-8")); return;
   case 1200: // UTF16LE
   case 1201: // UTF16BE
diff --git a/Source/util.h b/Source/util.h
index 71d1f06d..32fe9c12 100644
--- a/Source/util.h
+++ b/Source/util.h
@@ -140,7 +140,7 @@ int WinStdIO_wprintf(const wchar_t*Fmt, ...);
 #define _vftprintf WinStdIO_vfwprintf
 #endif // ~MAKENSIS
 #else
-int RunChildProcessRedirected(LPCWSTR cmd);
+int RunChildProcessRedirected(LPCSTR cmd);
 #endif // ~_UNICODE
 #define ResetPrintColor() FlushOutputAndResetPrintColor() // For reset ONLY, use PrintColorFmtMsg(0,NULL ...
 #define SetPrintColorWARN() PrintColorFmtMsg(1|0x10, NULL, (va_list)NULL)
@@ -274,10 +274,28 @@ FILE* my_fopen(const TCHAR *path, const char *mode);
 
 // round a value up to be a multiple of 512
 // assumption: T is an int type
-template <class T>
-inline T align_to_512(const T x) {
-  return (x+511) & ~511;
+template <class T> inline T align_to_512(const T x) { return (x+511) & ~511; }
+
+// some values need to be truncated from size_t to [unsigned] int, using this function is better than a plain cast
+template<class R, class T> inline R internaltruncate_cast(T t) {
+  assert((~((T)0)) > T(0)); // Only unsigned types supported right now
+  if (sizeof(T) > sizeof(R)) assert(t <= (T)(~((R)0))); // BUGBUG: What if R is a signed type?
+  return (R) t;
 }
+template<class R, class T> inline R debugtruncate_cast(T t,const char*f,unsigned int l) { 
+#ifdef MAKENSIS
+  if (sizeof(T) > sizeof(R) && !( (t <= (T)(~((R)0))) )) {
+    _tprintf(_T("unsafe truncate_cast: %") NPRIns _T(":%u\n"),f,l);
+    if (sizeof(T) <= sizeof(void*)) _tprintf(_T("\t0x%p > %0xp\n"),(void*)(UINT_PTR)(t),(void*)(UINT_PTR)(~((R)0)));
+  }
+#endif
+  return internaltruncate_cast<R>(t);
+}
+#if defined(DEBUG) || defined(_WIN64) // Always enabled for experimental 64-bit builds
+#define truncate_cast(ret_t,input) debugtruncate_cast<ret_t>((input),__FILE__,__LINE__)
+#else
+#define truncate_cast(ret_t,input) internaltruncate_cast<ret_t>((input))
+#endif
 
 // ================
 // ResourceManagers
diff --git a/Source/writer.cpp b/Source/writer.cpp
index cf5c66e7..d7e29fdf 100644
--- a/Source/writer.cpp
+++ b/Source/writer.cpp
@@ -96,9 +96,28 @@ void writer_sink::write_growbuf(const IGrowBuf *b)
   write_data(b->get(), b->getlen());
 }
 
+namespace hlp {
+  template<class T> static inline bool issigned() { return T(-1) < T(0); }
+  template<class T> static inline bool issigned(const T&t) { return issigned<T>(); }
+}
+
 void growbuf_writer_sink::write_data(const void *data, const size_t size)
 {
-  m_buf->add(data, BUGBUG64TRUNCATE(int, size));
+  // TODO: Replace all of this with a simple call when GrowBuf is changed to use size_t
+  if (sizeof(size) == sizeof(sink_type::size_type) && hlp::issigned(size) == hlp::issigned<sink_type::size_type>())
+  {
+    m_buf->add(data, truncate_cast(sink_type::size_type, size));
+  }
+  else
+  {
+    size_t left = size;
+    sink_type::size_type cbmaxadd = INT_MAX, cb;
+    for (char *p = (char *) data; left; p += cb, left -= cb)
+    {
+      cb = left >= (size_t) cbmaxadd ? cbmaxadd : (sink_type::size_type) left;
+      m_buf->add(p, cb);
+    }
+  }
 }
 
 void file_writer_sink::write_data(const void *data, const size_t size)
@@ -114,6 +133,6 @@ void file_writer_sink::write_data(const void *data, const size_t size)
 
 void crc_writer_sink::write_data(const void *data, const size_t size)
 {
-  *m_crc = CRC32(*m_crc, (const unsigned char *) data, BUGBUG64TRUNCATE(unsigned int, size));
+  *m_crc = CRC32(*m_crc, (const unsigned char *) data, size);
 }
 #endif
diff --git a/Source/writer.h b/Source/writer.h
index a2bfd999..bbc7b486 100644
--- a/Source/writer.h
+++ b/Source/writer.h
@@ -55,12 +55,13 @@ protected:
 
 class growbuf_writer_sink : public writer_sink {
 public:
-  growbuf_writer_sink(IGrowBuf *buf, bool build_unicode) : m_buf(buf) { m_build_unicode=build_unicode; }
+  typedef IGrowBuf sink_type;
+  growbuf_writer_sink(sink_type *buf, bool build_unicode) : m_buf(buf) { m_build_unicode=build_unicode; }
 
   virtual void write_data(const void *data, const size_t size);
 
 private:
-  IGrowBuf *m_buf;
+  sink_type *m_buf;
 
 };