static and shared library with MinGW

configure.ac

@@ -2624,19 +2624,17 @@ AX_HARDEN_CC_COMPILER_FLAGS
 # if mingw then link to ws2_32 for sockets
 case $host_os in
     mingw*)
-        LDFLAGS="$LDFLAGS -lws2_32" ;;
+        LDFLAGS="$LDFLAGS -lws2_32"
+        if test "$enable_shared" = "yes"
+        then
+            AC_DEFINE([WOLFSSL_DLL], [1], [Use __declspec(dllexport) when building library])
+            if test "$enable_static" = "yes"
+            then
+                MINGW_LIB_WARNING="yes"
+            fi
+        fi ;;
 esac
 
-# add wolfSSL defines for shared/static
-if test "$enable_shared" = "yes"
-then
-    AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_SHARED"
-fi
-if test "$enable_static" = "yes"
-then
-    AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_STATIC"
-fi
-
 # add user C_EXTRA_FLAGS back
 CFLAGS="$CFLAGS $USER_C_EXTRA_FLAGS"
 OPTION_FLAGS="$USER_CFLAGS $USER_C_EXTRA_FLAGS $AM_CFLAGS"
@@ -2879,8 +2877,31 @@ echo "   * Async Crypto:               $ENABLED_ASYNCCRYPT"
 echo ""
 echo "---"
 
+################################################################################
 # Show warnings at bottom so they are noticed
+################################################################################
+
 if test "$ENABLED_ASYNCCRYPT" = "yes"
 then
     AC_MSG_WARN([Make sure real async files are loaded. Contact wolfSSL for details on using the asynccrypt option.])
 fi
+
+# MinGW static vs shared library
+# The URL I was looking at for this was
+# http://www.gnu.org/software/libtool/manual/libtool.html#Cygwin-to-MinGW-Cross
+# this allows for not even having dllimport/dllexport on functions
+# with recent libtools, only requiring it with global variables.
+# The warning is displayed here because if not using "contemporary GNU
+# tools" there is the possibility of export/import issues.
+# We use __declspec(dllexport) and "contemporary GNU tools" are taking care
+# of the case where both static and shared libraries are built. It is also
+# placing both __imp__function and function in the lib.dll.a created. Allowing
+# users to choose if they use __declspec(dllimport) with defining WOLFSSL_DLL.
+#
+# More can be found about the MinGW linker at
+# https://sourceware.org/binutils/docs/ld/WIN32.html
+if test "$MINGW_LIB_WARNING" = "yes"
+then
+    AC_MSG_WARN([Building with shared and static library at the same time on this system may cause export/import problems when using non contemporary GNU tools.])
+fi
+

wolfssl/wolfcrypt/visibility.h

@@ -46,9 +46,8 @@
     #elif defined(__SUNPRO_C) && (__SUNPRO_C >= 0x550)
         #define WOLFSSL_API   __global
         #define WOLFSSL_LOCAL __hidden
-    #elif defined(_MSC_VER)
+    #elif defined(_MSC_VER) || defined(__MINGW32__)
-        #if defined(WOLFSSL_DLL) || \
+        #if defined(WOLFSSL_DLL)
-            (defined(__MINGW32__) && defined(WOLFSSL_SHARED))
             #define WOLFSSL_API __declspec(dllexport)
         #else
             #define WOLFSSL_API
@@ -59,9 +58,8 @@
         #define WOLFSSL_LOCAL
     #endif /* HAVE_VISIBILITY */
 #else /* BUILDING_WOLFSSL */
-    #if defined(_MSC_VER)
+    #if defined(_MSC_VER) || defined(__MINGW32__)
-        #if defined(WOLFSSL_DLL) || \
+        #if defined(WOLFSSL_DLL)
-            (defined(__MINGW32__) && defined(WOLFSSL_SHARED))
             #define WOLFSSL_API __declspec(dllimport)
         #else
             #define WOLFSSL_API