diff -Nur mpdecimal-2.5.1-orig/configure.ac mpdecimal-2.5.1/configure.ac
--- mpdecimal-2.5.1-orig/configure.ac	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/configure.ac	2021-08-28 16:41:17.444914500 +0200
@@ -198,6 +198,7 @@
 LIBSTATIC=libmpdec.a
 LIBSHARED_USE_AR="no"
 LIBIMPORT=
+IS_WINDOWS=no
 LINK_STATIC=
 LINK_DYNAMIC=
 LINK_SHLIBS="-lmpdec"
@@ -219,6 +220,22 @@
         LINK_DYNAMIC="-Wl,-bshared"
         LINK_SHLIBS="../libmpdec/$LIBIMPORT"
         ;;
+    mingw*|MINGW*)
+        LIBNAME=
+        LIBIMPORT="libmpdec.dll.a"
+        LIBSONAME=
+        LIBSHARED="libmpdec-2.dll"
+        CONFIGURE_LDFLAGS="-shared -Wl,--out-implib,$LIBIMPORT"
+        IS_WINDOWS=yes
+        ;;
+    msys*|MSYS*)
+        LIBNAME=
+        LIBIMPORT="libmpdec.dll.a"
+        LIBSONAME=
+        LIBSHARED="msys-mpdec-2.dll"
+        CONFIGURE_LDFLAGS="-shared -Wl,--out-implib,$LIBIMPORT"
+        IS_WINDOWS=yes
+        ;;
     *)
         LIBNAME="libmpdec.so"
         LIBSONAME="libmpdec.so.3"
@@ -228,6 +245,7 @@
 esac
 
 LIBSTATIC_CXX=libmpdec++.a
+LIBIMPORT_CXX=
 LINK_SHLIBS_CXX="-lmpdec++"
 case $ac_sys_system in
     darwin*|Darwin*)
@@ -242,6 +260,20 @@
         LIBSHARED_CXX="shr.o"
         CONFIGURE_LDXXFLAGS="-shared -Wl,-bnoentry -Wl,-bE:.objs/symbols.exp"
         ;;
+    mingw*|MINGW*)
+        LIBNAME_CXX=
+        LIBIMPORT_CXX="libmpdec++.dll.a"
+        LIBSONAME_CXX=
+        LIBSHARED_CXX="libmpdec++-2.dll"
+        CONFIGURE_LDXXFLAGS="-shared -Wl,--out-implib,$LIBIMPORT_CXX"
+        ;;
+    msys*|MSYS*)
+        LIBNAME_CXX=
+        LIBIMPORT_CXX="libmpdec++.dll.a"
+        LIBSONAME_CXX=
+        LIBSHARED_CXX="msys-mpdec++-2.dll"
+        CONFIGURE_LDXXFLAGS="-shared -Wl,--out-implib,$LIBIMPORT_CXX"
+        ;;
     *)
         LIBNAME_CXX="libmpdec++.so"
         LIBSONAME_CXX="libmpdec++.so.3"
@@ -255,6 +287,7 @@
 AC_SUBST(LIBSONAME)
 AC_SUBST(LIBSHARED)
 AC_SUBST(LIBIMPORT)
+AC_SUBST(IS_WINDOWS)
 AC_SUBST(LIBSHARED_USE_AR)
 AC_SUBST(LINK_STATIC)
 AC_SUBST(LINK_DYNAMIC)
@@ -264,6 +297,7 @@
 AC_SUBST(LIBNAME_CXX)
 AC_SUBST(LIBSONAME_CXX)
 AC_SUBST(LIBSHARED_CXX)
+AC_SUBST(LIBIMPORT_CXX)
 AC_SUBST(LINK_SHLIBS_CXX)
 
 # Apparently purely informational for this particular build:
diff -Nur mpdecimal-2.5.1-orig/libmpdec/Makefile.in mpdecimal-2.5.1/libmpdec/Makefile.in
--- mpdecimal-2.5.1-orig/libmpdec/Makefile.in	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/libmpdec/Makefile.in	2021-08-28 16:51:47.066899100 +0200
@@ -10,6 +10,7 @@
 LIBSONAME = @LIBSONAME@
 LIBSHARED = @LIBSHARED@
 LIBIMPORT = @LIBIMPORT@
+IS_WINDOWS= @IS_WINDOWS@
 LIBSHARED_USE_AR = @LIBSHARED_USE_AR@
 LINK_STATIC = @LINK_STATIC@
 LINK_DYNAMIC = @LINK_DYNAMIC@
@@ -84,9 +85,11 @@
 
 $(LIBSHARED): Makefile $(SHARED_OBJS)
 	$(LD) $(MPD_LDFLAGS) -o $(LIBSHARED) $(SHARED_OBJS) -lm
+ifeq ($(IS_WINDOWS),no)
 	ln -sf $(LIBSHARED) $(LIBNAME)
 	ln -sf $(LIBSHARED) $(LIBSONAME)
 endif
+endif
 
 
 basearith.o:\
diff -Nur mpdecimal-2.5.1-orig/libmpdec++/Makefile.in mpdecimal-2.5.1/libmpdec++/Makefile.in
--- mpdecimal-2.5.1-orig/libmpdec++/Makefile.in	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/libmpdec++/Makefile.in	2021-08-28 16:52:35.175574300 +0200
@@ -9,11 +9,14 @@
 LIBNAME = @LIBNAME@
 LIBSONAME = @LIBSONAME@
 LIBSHARED = @LIBSHARED@
+LIBIMPORT = @LIBIMPORT@
+IS_WINDOWS= @IS_WINDOWS@
 
 LIBSTATIC_CXX = @LIBSTATIC_CXX@
 LIBNAME_CXX = @LIBNAME_CXX@
 LIBSONAME_CXX = @LIBSONAME_CXX@
 LIBSHARED_CXX = @LIBSHARED_CXX@
+LIBIMPORT_CXX = @LIBIMPORT_CXX@
 LIBSHARED_USE_AR = @LIBSHARED_USE_AR@
 LINK_STATIC = @LINK_STATIC@
 LINK_DYNAMIC = @LINK_DYNAMIC@
@@ -74,10 +77,14 @@
 	$(RANLIB) $(LIBSTATIC_CXX)
 
 $(LIBSHARED_CXX): Makefile $(SHARED_OBJS)
+ifeq ($(IS_WINDOWS),yes)
+	$(LDXX) $(MPD_LDXXFLAGS) -o $(LIBSHARED_CXX) $(SHARED_OBJS) ../libmpdec/$(LIBIMPORT) -lm
+else
 	$(MPD_LDXX) -L../libmpdec $(MPD_LDXXFLAGS) -o $(LIBSHARED_CXX) $(SHARED_OBJS) -lmpdec -lm
 	ln -sf $(LIBSHARED_CXX) $(LIBNAME_CXX)
 	ln -sf $(LIBSHARED_CXX) $(LIBSONAME_CXX)
 endif
+endif
 
 
 decimal.o:\
diff -Nur mpdecimal-2.5.1-orig/Makefile.in mpdecimal-2.5.1/Makefile.in
--- mpdecimal-2.5.1-orig/Makefile.in	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/Makefile.in	2021-08-28 16:43:00.149589100 +0200
@@ -16,17 +16,20 @@
 LIBSONAME = @LIBSONAME@
 LIBSHARED = @LIBSHARED@
 LIBIMPORT = @LIBIMPORT@
+IS_WINDOWS= @IS_WINDOWS@
 
 LIBSTATIC_CXX = @LIBSTATIC_CXX@
 LIBNAME_CXX = @LIBNAME_CXX@
 LIBSONAME_CXX = @LIBSONAME_CXX@
 LIBSHARED_CXX = @LIBSHARED_CXX@
+LIBIMPORT_CXX = @LIBIMPORT_CXX@
 
 LIBSHARED_USE_AR = @LIBSHARED_USE_AR@
 
 prefix = @prefix@
 exec_prefix = @exec_prefix@
 includedir = @includedir@
+bindir = @bindir@
 libdir = @libdir@
 datarootdir = @datarootdir@
 docdir = @docdir@
@@ -48,7 +51,7 @@
 	cd libmpdec++ && $(MAKE) check_alloc
 
 ifeq ($(LIBSHARED_USE_AR), yes)
-install: install_libcxx install_imp install_cxx_doc
+install: install_libcxx install_impcxx install_cxx_doc
 else
 ifeq ($(ENABLE_SHARED), yes)
 install: install_shared_libcxx install_cxx_doc
@@ -96,8 +99,14 @@
 	$(INSTALL) -m 644 libmpdec/$(LIBSTATIC) $(DESTDIR)$(libdir)
 
 install_shared_lib: install_lib
+ifeq ($(IS_WINDOWS),yes)
+	$(INSTALL) -d -m 755 $(DESTDIR)$(bindir)
+	$(INSTALL) -m 655 libmpdec/$(LIBIMPORT) $(DESTDIR)$(libdir)
+	$(INSTALL) -m 755 libmpdec/$(LIBSHARED) $(DESTDIR)$(bindir)
+else
 	$(INSTALL) -m 755 libmpdec/$(LIBSHARED) $(DESTDIR)$(libdir)
 	cd $(DESTDIR)$(libdir) && ln -sf $(LIBSHARED) $(LIBSONAME) && ln -sf $(LIBSHARED) $(LIBNAME)
+endif
 
 install_imp:
 	$(INSTALL) -m 644 libmpdec/$(LIBIMPORT) $(DESTDIR)$(libdir)
@@ -113,8 +122,14 @@
 	$(INSTALL) -m 644 libmpdec++/$(LIBSTATIC_CXX) $(DESTDIR)$(libdir)
 
 install_shared_libcxx: install_shared_lib install_libcxx
+ifeq ($(IS_WINDOWS),yes)
+	$(INSTALL) -d -m 755 $(DESTDIR)$(bindir)
+	$(INSTALL) -m 644 libmpdec++/$(LIBIMPORT_CXX) $(DESTDIR)$(libdir)
+	$(INSTALL) -m 755 libmpdec++/$(LIBSHARED_CXX) $(DESTDIR)$(bindir)
+else
 	$(INSTALL) -m 755 libmpdec++/$(LIBSHARED_CXX) $(DESTDIR)$(libdir)
 	cd $(DESTDIR)$(libdir) && ln -sf $(LIBSHARED_CXX) $(LIBSONAME_CXX) && ln -sf $(LIBSHARED_CXX) $(LIBNAME_CXX)
+endif
 
 install_cxx_doc: install_doc
 	cp -Rp doc/libmpdec++ $(DESTDIR)$(docdir)
diff -Nur mpdecimal-2.5.1-orig/tests/Makefile.in mpdecimal-2.5.1/tests/Makefile.in
--- mpdecimal-2.5.1-orig/tests/Makefile.in	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/tests/Makefile.in	2021-08-28 16:46:42.826010700 +0200
@@ -15,6 +15,9 @@
 
 MPD_GNU99 = @MPD_GNU99@
 
+# Windows demands some special build rules.
+IS_WINDOWS = @IS_WINDOWS@
+
 CONFIGURE_CFLAGS = @CONFIGURE_CFLAGS@
 MPD_CFLAGS = $(strip $(filter-out $(CFLAGS),$(CONFIGURE_CFLAGS)) $(CFLAGS) $(MPD_GNU99))
 
@@ -52,6 +55,9 @@
 clean: FORCE
 	rm -f *.o *.gch *.gcda *.gcno *.gcov *.dyn *.dpi *.lock
 	rm -f runtest runtest_shared
+ifeq ($(IS_WINDOWS),yes)
+	rm -f *.dll *.exe
+endif
 
 distclean: FORCE
 	$(MAKE) clean
diff -Nur mpdecimal-2.5.1-orig/tests/runshort.sh mpdecimal-2.5.1/tests/runshort.sh
--- mpdecimal-2.5.1-orig/tests/runshort.sh	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/tests/runshort.sh	2021-08-28 18:50:12.073569400 +0200
@@ -46,6 +46,7 @@
 
 LD_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec"
 LD_32_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec"
+PATH="$LD_LIBRARY_PATH:$PATH"
 export LD_LIBRARY_PATH
 export LD_32_LIBRARY_PATH
 
diff -Nur mpdecimal-2.5.1-orig/tests/runshort_alloc.sh mpdecimal-2.5.1/tests/runshort_alloc.sh
--- mpdecimal-2.5.1-orig/tests/runshort_alloc.sh	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/tests/runshort_alloc.sh	2021-08-28 16:58:55.526592500 +0200
@@ -44,6 +44,7 @@
 
 LD_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec"
 LD_32_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec"
+PATH="$LD_LIBRARY_PATH:$PATH"
 export LD_LIBRARY_PATH
 export LD_32_LIBRARY_PATH
 
diff -Naur mpdecimal-2.5.0-orig/tests/runtest.c mpdecimal-2.5.0/tests/runtest.c
--- mpdecimal-2.5.0-orig/tests/runtest.c	2020-06-27 22:41:49.000000000 +0300
+++ mpdecimal-2.5.0/tests/runtest.c	2020-07-16 09:18:19.834286900 +0300
@@ -46,6 +46,10 @@
 
 #include "malloc_fail.h"
 
+#if defined(__MINGW32__)
+#define random rand
+#define srandom srand
+#endif
 
 #define MAXLINE 400000
 #define MAXTOKEN 32
diff -Nur mpdecimal-2.5.1-orig/tests++/runshort.sh mpdecimal-2.5.1/tests++/runshort.sh
--- mpdecimal-2.5.1-orig/tests++/runshort.sh	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/tests++/runshort.sh	2021-08-28 17:02:19.339551800 +0200
@@ -63,6 +63,7 @@
 
 LD_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec:$PORTABLE_PWD/../libmpdec++"
 LD_32_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec:$PORTABLE_PWD/../libmpdec++"
+PATH="$LD_LIBRARY_PATH:$PATH"
 export LD_LIBRARY_PATH
 export LD_32_LIBRARY_PATH
 
diff -Nur mpdecimal-2.5.1-orig/tests++/runshort_alloc.sh mpdecimal-2.5.1/tests++/runshort_alloc.sh
--- mpdecimal-2.5.1-orig/tests++/runshort_alloc.sh	2021-01-20 15:07:31.000000000 +0100
+++ mpdecimal-2.5.1/tests++/runshort_alloc.sh	2021-08-28 17:02:28.555004800 +0200
@@ -61,6 +61,7 @@
 
 LD_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec:$PORTABLE_PWD/../libmpdec++"
 LD_32_LIBRARY_PATH="$PORTABLE_PWD/../libmpdec:$PORTABLE_PWD/../libmpdec++"
+PATH="$LD_LIBRARY_PATH:$PATH"
 export LD_LIBRARY_PATH
 export LD_32_LIBRARY_PATH