diff --git a/Contrib/Library/LibraryLocal/LibraryLocal.cpp b/Contrib/Library/LibraryLocal/LibraryLocal.cpp
index 110411b8..cf4807a8 100644
--- a/Contrib/Library/LibraryLocal/LibraryLocal.cpp
+++ b/Contrib/Library/LibraryLocal/LibraryLocal.cpp
@@ -150,8 +150,8 @@ int _tmain(int argc, TCHAR* argv[])
   }
   else
   {
-    fprintf(fHdr, "!define LIBRARY_VERSION_HIGH %u\n", high);
-    fprintf(fHdr, "!define LIBRARY_VERSION_LOW %u\n", low);
+    fprintf(fHdr, "!define LIBRARY_VERSION_HIGH %lu\n", high);
+    fprintf(fHdr, "!define LIBRARY_VERSION_LOW %lu\n", low);
   }
 
   fclose(fHdr);
diff --git a/Contrib/Makensisw/makensisw.cpp b/Contrib/Makensisw/makensisw.cpp
index ab66cdf7..2bf2ef19 100644
--- a/Contrib/Makensisw/makensisw.cpp
+++ b/Contrib/Makensisw/makensisw.cpp
@@ -768,7 +768,7 @@ DWORD WINAPI MakeNSISProc(LPVOID TreadParam) {
     }
     char oddbyte = (char)(cb % 2), incompsurr;
     cbofs = 0;
-    if (incompsurr = IS_HIGH_SURROGATE(p[cch-1]))
+    if ((incompsurr = IS_HIGH_SURROGATE(p[cch-1])))
       wcl = p[--cch], cbofs = sizeof(WCHAR); // Store leading surrogate part and complete it later
     if (oddbyte)
       oddbyte = iob[cb-1], ++cbofs;
diff --git a/Contrib/System/SConscript b/Contrib/System/SConscript
index 0dc36609..676096b0 100644
--- a/Contrib/System/SConscript
+++ b/Contrib/System/SConscript
@@ -39,17 +39,19 @@ if env['TARGET_ARCH'] != 'amd64' or msvc: # BUGBUG: Call-amd64.S is missing GAS
 	filename = 'Call' + srcsuff
 
 	src_ascpp = """
-		#if 1 /* a C style comment */
-		.end
+		#if 0 /* a C style comment */
+		ERROR: assembler-with-cpp required!
 		#else
-		ERROR!
+		.end
 		#endif
 	"""
 	conf = env.Configure()
 	if conf.TryCompile('END', '.S'):
 		files += ['Source/'+filename+'.S']
-	elif conf.TryCompile(src_ascpp, '.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()
diff --git a/Contrib/System/Source/CallCPP.S b/Contrib/System/Source/CallCPP.S
index 0f0a5543..72f68c77 100644
--- a/Contrib/System/Source/CallCPP.S
+++ b/Contrib/System/Source/CallCPP.S
@@ -1,4 +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.S"
+#endif
diff --git a/Contrib/System/Source/CallCPP.sx b/Contrib/System/Source/CallCPP.sx
new file mode 100644
index 00000000..c821f056
--- /dev/null
+++ b/Contrib/System/Source/CallCPP.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 "CallCPP.S"
+#endif
diff --git a/Contrib/System/Source/System.c b/Contrib/System/Source/System.c
index 4aafbe79..fccfc704 100644
--- a/Contrib/System/Source/System.c
+++ b/Contrib/System/Source/System.c
@@ -448,11 +448,6 @@ __int64 GetIntFromString(TCHAR **p)
     return myatoi64(buffer);
 }
 
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wuninitialized" // temp3 is set to 0 when we start parsing a new parameter
-// must be outside of function for mingw
-#endif
 SystemProc *PrepareProc(BOOL NeedForCall)
 {
     int SectionType = PST_PROC, // First section is always proc spec
@@ -466,6 +461,10 @@ SystemProc *PrepareProc(BOOL NeedForCall)
     TCHAR *ibuf, *ib, *sbuf, *cbuf, *cb;
     unsigned int UsedTString = 0;
 
+#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) < 4006
+    temp3 = 0; // "warning: 'temp3' may be used uninitialized in this function": temp3 is set to 0 when we start parsing a new parameter
+#endif
+
     // Retrieve proc specs
     cb = (cbuf = AllocString()); // Current String buffer
     sbuf = AllocString(); // Safe String buffer
@@ -693,7 +692,14 @@ 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
@@ -762,7 +768,14 @@ 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;
@@ -910,9 +923,6 @@ SystemProc *PrepareProc(BOOL NeedForCall)
 
     return proc;
 }
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif
 
 void ParamAllocate(SystemProc *proc)
 {
diff --git a/Source/build.cpp b/Source/build.cpp
index 4eb10d43..55113413 100644
--- a/Source/build.cpp
+++ b/Source/build.cpp
@@ -2993,7 +2993,7 @@ int CEXEBuild::write_output(void)
           ERROR_MSG(_T("Error: can't allocate memory for finalize command\n"));
           return PS_ERROR;
         }
-        *((unsigned char**)&arg) -= (UINT_PTR)cmdstr, *((unsigned char**)&arg) += (UINT_PTR)cmdstrbuf;
+        arg -= ((UINT_PTR)cmdstr)/sizeof(TCHAR), arg += ((UINT_PTR)cmdstrbuf)/sizeof(TCHAR);
         _tcscpy(cmdstrbuf,cmdstr);
         cmdstr = cmdstrbuf;
         memmove(arg+cchbldoutfile, arg+2, (_tcslen(arg+2)+1)*sizeof(TCHAR));
diff --git a/Source/exehead/Main.c b/Source/exehead/Main.c
index 44864ffa..4c01c4cc 100644
--- a/Source/exehead/Main.c
+++ b/Source/exehead/Main.c
@@ -362,9 +362,9 @@ end:
     }
 
     IS=myGetProcAddress(MGA_InitiateShutdown);
-    if (IS && !IS(NULL, NULL, 0, SHUTDOWN_RESTART | SHUTDOWN_FORCE_OTHERS | SHUTDOWN_GRACE_OVERRIDE, reason)
-     || !ExitWindowsEx(EWX_REBOOT, reason)
-    )
+    if ( (IS && !IS(NULL, NULL, 0, SHUTDOWN_RESTART | SHUTDOWN_FORCE_OTHERS | SHUTDOWN_GRACE_OVERRIDE, reason))
+      || (!ExitWindowsEx(EWX_REBOOT, reason))
+      )
       ExecuteCallbackFunction(CB_ONREBOOTFAILED);
   }
 #endif//NSIS_SUPPORT_REBOOT
diff --git a/Source/exehead/Ui.c b/Source/exehead/Ui.c
index 8e7b06dd..b86e7718 100644
--- a/Source/exehead/Ui.c
+++ b/Source/exehead/Ui.c
@@ -1031,6 +1031,10 @@ static INT_PTR CALLBACK DirProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM l
     int available_set = 0;
     unsigned total, available;
 
+#if defined(__GNUC__) && ((__GNUC__ * 1000) + __GNUC_MINOR__) < 4006
+    available = 0; // warning: 'available' may be used uninitialized in this function
+#endif
+
     GetUIText(IDC_DIR,dir);
     if (!is_valid_instpath(dir))
       error = NSIS_INSTDIR_INVALID;
diff --git a/Source/script.cpp b/Source/script.cpp
index a3f59d15..f46155b0 100644
--- a/Source/script.cpp
+++ b/Source/script.cpp
@@ -1400,7 +1400,7 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
 
     case TOK_P_APPENDFILE:
       {
-        WORD tok = 0, cp;
+        WORD tok = 0, cp = 0;
         bool bom = false, forceEnc = false;
         TCHAR *param = line.gettoken_str(++tok), buf[9+1];
         my_strncpy(buf,param,COUNTOF(buf));
diff --git a/Source/util.cpp b/Source/util.cpp
index 57eb966d..461b9e4b 100644
--- a/Source/util.cpp
+++ b/Source/util.cpp
@@ -722,7 +722,7 @@ tstring& path_append_separator(tstring& path)
 {
   tstring::iterator ib = path.begin(), ie = path.end();
   if (ib != ie && !IsPathSeparator(*--ie))
-    path.push_back(PLATFORM_PATH_SEPARATOR_C);
+    path += PLATFORM_PATH_SEPARATOR_STR;
   return path;
 }
 
diff --git a/Source/writer.cpp b/Source/writer.cpp
index f083e34a..11da07c1 100644
--- a/Source/writer.cpp
+++ b/Source/writer.cpp
@@ -62,7 +62,7 @@ void writer_sink::write_string(const TCHAR *s, size_t size)
   if (m_build_unicode)
   {
     bool strEnd = false;
-    TCHAR ch;
+    TCHAR ch = L'\0';
     for (; size ; size--)
     {
       if (!strEnd)