diff --git a/include/wx/filefn.h b/include/wx/filefn.h
index 4815807f60..6cf2548880 100644
--- a/include/wx/filefn.h
+++ b/include/wx/filefn.h
@@ -216,8 +216,22 @@ enum wxPosixPermissions
         #define wxFtell _ftelli64
     #elif wxCHECK_MINGW32_VERSION(3, 5) // mingw-runtime version (not gcc)
         #define wxHAS_HUGE_STDIO_FILES
+
+        wxDECL_FOR_STRICT_MINGW32(int, fseeko64, (FILE*, long long, int));
         #define wxFseek fseeko64
-        #define wxFtell ftello64
+
+        #ifdef wxNEEDS_STRICT_ANSI_WORKAROUNDS
+            // Unfortunately ftello64() is not defined in the library for
+            // whatever reason but as an inline function, so define wxFtell()
+            // here similarly.
+            inline long long wxFtell(FILE* fp)
+            {
+                fpos_t pos;
+                return fgetpos(fp, &pos) == 0 ? pos : -1LL;
+            }
+        #else
+            #define wxFtell ftello64
+        #endif
     #endif
 
     // other Windows compilers (DMC, Watcom, and Borland) don't have huge file
@@ -376,7 +390,7 @@ enum wxPosixPermissions
 
     // finally the default char-type versions
     #if wxUSE_UNICODE
-        #if wxUSE_UNICODE_MSLU || defined(__WX_STRICT_ANSI_GCC__)
+        #if wxUSE_UNICODE_MSLU
             // implement the missing file functions in Win9x ourselves
             WXDLLIMPEXP_BASE int wxMSLU__wopen(const wxChar *name,
                                                int flags, int mode);
@@ -404,6 +418,9 @@ enum wxPosixPermissions
             #define wxCRT_MkDir     wxCRT_MkDirW
             #define wxCRT_RmDir     wxCRT_RmDirW
             #define wxCRT_Stat      wxCRT_StatW
+
+            wxDECL_FOR_STRICT_MINGW32(int, _wmkdir, (const wchar_t*))
+            wxDECL_FOR_STRICT_MINGW32(int, _wrmdir, (const wchar_t*))
         #endif // wxUSE_UNICODE_MSLU/!wxUSE_UNICODE_MSLU
     #else // !wxUSE_UNICODE
         #define wxCRT_Open      wxCRT_OpenA
diff --git a/include/wx/math.h b/include/wx/math.h
index 89a1b94473..909764a41f 100644
--- a/include/wx/math.h
+++ b/include/wx/math.h
@@ -71,6 +71,10 @@
     #else
         #define wxFinite(x) isfinite(x)
     #endif
+#elif defined(wxNEEDS_STRICT_ANSI_WORKAROUNDS)
+    wxDECL_FOR_STRICT_MINGW32(int, _finite, (double));
+
+    #define wxFinite(x) _finite(x)
 #elif ( defined(__GNUG__)||defined(__GNUWIN32__)||defined(__DJGPP__)|| \
       defined(__SGI_CC__)||defined(__SUNCC__)||defined(__XLC__)|| \
       defined(__HPUX__) ) && ( !defined(wxOSX_USE_IPHONE) || wxOSX_USE_IPHONE == 0 )
diff --git a/include/wx/msw/gccpriv.h b/include/wx/msw/gccpriv.h
index c1962799a6..c2b4b735c3 100644
--- a/include/wx/msw/gccpriv.h
+++ b/include/wx/msw/gccpriv.h
@@ -156,5 +156,28 @@
     #endif
 #endif
 
+/*
+    Traditional MinGW (but not MinGW-w64 nor TDM-GCC) omits many POSIX
+    functions from their headers when compiled with __STRICT_ANSI__ defined.
+    Unfortunately this means that they are not available when using -std=c++98
+    (not very common) or -std=c++11 (much more so), but we still need them even
+    in this case. As the intention behind using -std=c++11 is probably to get
+    the new C++11 features and not disable the use of POSIX functions, we just
+    manually declare the functions we need in this case if necessary.
+ */
+#if defined(__MINGW32_TOOLCHAIN__) && defined(__STRICT_ANSI__)
+    #define wxNEEDS_STRICT_ANSI_WORKAROUNDS
+
+    /*
+        This macro is somewhat unusual as it takes the list of parameters
+        inside parentheses and includes semicolon inside it as putting the
+        semicolon outside wouldn't do the right thing when this macro is empty.
+     */
+    #define wxDECL_FOR_STRICT_MINGW32(rettype, func, params) \
+        extern "C" _CRTIMP rettype __cdecl __MINGW_NOTHROW func params ;
+#else
+    #define wxDECL_FOR_STRICT_MINGW32(rettype, func, params)
+#endif
+
 #endif
   /* _WX_MSW_GCCPRIV_H_ */
diff --git a/include/wx/msw/private.h b/include/wx/msw/private.h
index a6b3f76396..27c5fb4244 100644
--- a/include/wx/msw/private.h
+++ b/include/wx/msw/private.h
@@ -183,6 +183,8 @@ extern LONG APIENTRY _EXPORT
    || defined(__MINGW32__)
     #define wxGetOSFHandle(fd) ((HANDLE)_get_osfhandle(fd))
     #define wxOpenOSFHandle(h, flags) (_open_osfhandle(wxPtrToUInt(h), flags))
+
+    wxDECL_FOR_STRICT_MINGW32(FILE*, _fdopen, (int, const char*))
     #define wx_fdopen _fdopen
 #endif
 
diff --git a/include/wx/wxcrtbase.h b/include/wx/wxcrtbase.h
index 1c3522ec66..4ebe8c212e 100644
--- a/include/wx/wxcrtbase.h
+++ b/include/wx/wxcrtbase.h
@@ -73,6 +73,9 @@
 
 #ifdef wxNEED_ISASCII
     inline int isascii(int c) { return (unsigned)c < 0x80; }
+
+    // Avoid further (re)definitions of it.
+    #define isascii isascii
 #endif
 
 #ifdef _WIN32_WCE
@@ -445,7 +448,7 @@ WXDLLIMPEXP_BASE wchar_t *wxCRT_StrtokW(wchar_t *psz, const wchar_t *delim, wcha
 #else /* Unicode filenames */
     /* special case: these functions are missing under Win9x with Unicows so we
        have to implement them ourselves */
-    #if wxUSE_UNICODE_MSLU || defined(__WX_STRICT_ANSI_GCC__)
+    #if wxUSE_UNICODE_MSLU
             WXDLLIMPEXP_BASE FILE* wxMSLU__wfopen(const wchar_t *name, const wchar_t *mode);
             WXDLLIMPEXP_BASE FILE* wxMSLU__wfreopen(const wchar_t *name, const wchar_t *mode, FILE *stream);
             WXDLLIMPEXP_BASE int wxMSLU__wrename(const wchar_t *oldname, const wchar_t *newname);
@@ -455,6 +458,11 @@ WXDLLIMPEXP_BASE wchar_t *wxCRT_StrtokW(wchar_t *psz, const wchar_t *delim, wcha
             #define wxCRT_Remove    wxMSLU__wremove
             #define wxCRT_Rename    wxMSLU__wrename
     #else
+        wxDECL_FOR_STRICT_MINGW32(FILE*, _wfopen, (const wchar_t*, const wchar_t*))
+        wxDECL_FOR_STRICT_MINGW32(FILE*, _wfreopen, (const wchar_t*, const wchar_t*, FILE*))
+        wxDECL_FOR_STRICT_MINGW32(int, _wrename, (const wchar_t*, const wchar_t*))
+        wxDECL_FOR_STRICT_MINGW32(int, _wremove, (const wchar_t*))
+
         /* WinCE CRT doesn't provide these functions so use our own */
         #ifdef __WXWINCE__
             WXDLLIMPEXP_BASE int wxCRT_Rename(const wchar_t *src,
diff --git a/src/common/filefn.cpp b/src/common/filefn.cpp
index bfa1efa172..f563a1a5ea 100644
--- a/src/common/filefn.cpp
+++ b/src/common/filefn.cpp
@@ -90,6 +90,8 @@
     #define HAVE_WGETCWD
 #endif
 
+wxDECL_FOR_STRICT_MINGW32(int, _fileno, (FILE*))
+
 // ----------------------------------------------------------------------------
 // constants
 // ----------------------------------------------------------------------------
diff --git a/src/common/time.cpp b/src/common/time.cpp
index 011b601490..0b6bd35e10 100644
--- a/src/common/time.cpp
+++ b/src/common/time.cpp
@@ -22,6 +22,23 @@
     #pragma hdrstop
 #endif
 
+// This is a horrible hack which only works because we don't currently include
+// <time.h> from wx/wxprec.h. It is needed because we need timezone-related
+// stuff from MinGW time.h, but it is not compiled in strict ANSI mode and it
+// is too complicated to be dealt with using wxDECL_FOR_STRICT_MINGW32(). So we
+// just include the header after undefining __STRICT_ANSI__ to get all the
+// declarations we need -- and then define it back to avoid inconsistencies in
+// all our other headers.
+//
+// Note that the same hack is used for "environ" in utilscmn.cpp, so if the
+// code here is modified because this hack becomes unnecessary or a better
+// solution is found, the code there should be updated as well.
+#ifdef wxNEEDS_STRICT_ANSI_WORKAROUNDS
+    #undef __STRICT_ANSI__
+    #include <time.h>
+    #define __STRICT_ANSI__
+#endif
+
 #include "wx/time.h"
 
 #ifndef WX_PRECOMP
diff --git a/src/common/utilscmn.cpp b/src/common/utilscmn.cpp
index 6c7d0c351a..a83ab45bf7 100644
--- a/src/common/utilscmn.cpp
+++ b/src/common/utilscmn.cpp
@@ -23,6 +23,14 @@
     #pragma hdrstop
 #endif
 
+// See comment about this hack in time.cpp: here we do it for environ external
+// variable which can't be easily declared when using MinGW in strict ANSI mode.
+#ifdef wxNEEDS_STRICT_ANSI_WORKAROUNDS
+    #undef __STRICT_ANSI__
+    #include <stdlib.h>
+    #define __STRICT_ANSI__
+#endif
+
 #ifndef WX_PRECOMP
     #include "wx/app.h"
     #include "wx/string.h"
diff --git a/src/common/wxcrt.cpp b/src/common/wxcrt.cpp
index 29ecbaa552..b58b72830d 100644
--- a/src/common/wxcrt.cpp
+++ b/src/common/wxcrt.cpp
@@ -73,6 +73,10 @@
     #include <xlocale.h>
 #endif
 
+wxDECL_FOR_STRICT_MINGW32(int, vswprintf, (wchar_t*, const wchar_t*, __VALIST));
+wxDECL_FOR_STRICT_MINGW32(int, _putws, (const wchar_t*));
+wxDECL_FOR_STRICT_MINGW32(void, _wperror, (const wchar_t*));
+
 WXDLLIMPEXP_BASE size_t wxMB2WC(wchar_t *buf, const char *psz, size_t n)
 {
   // assume that we have mbsrtowcs() too if we have wcsrtombs()
diff --git a/src/stc/scintilla/include/Scintilla.h b/src/stc/scintilla/include/Scintilla.h
index 3cacd53101..616e93f9b6 100644
--- a/src/stc/scintilla/include/Scintilla.h
+++ b/src/stc/scintilla/include/Scintilla.h
@@ -42,6 +42,17 @@ typedef long sptr_t;
 
 typedef sptr_t (*SciFnDirect)(sptr_t ptr, unsigned int iMessage, uptr_t wParam, sptr_t lParam);
 
+/* Workaround for building with MinGW (not MinGW-w64) in strict ANSI mode which
+ * is, notably, enabled by -std=c++NN options. */
+#if defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && defined(__STRICT_ANSI__)
+/* Other headers included by an application using Scintilla might already
+ * define isascii() too, for the same reasons, try to play nicely with the. */
+#ifndef isascii
+inline int isascii(int c) { return !(c & ~0x7F); }
+#define isascii isascii
+#endif
+#endif
+
 /* ++Autogenerated -- start of section automatically generated from Scintilla.iface */
 #define INVALID_POSITION -1
 #define SCI_START 2000