Fix wifi cannot configure as default network interface

connectivity/drivers/wifi/COMPONENT_ESPRESSIF_ESP8266/CMakeLists.txt

@@ -12,3 +12,15 @@ target_include_directories(mbed-wifi
         .
         ./ESP8266
 )
+
+# Link override object file coming from static library anyway
+#
+# NOTE: This linker option is to pretend undefined symbol and won't cause
+#       undefined symbol error even though the override object file actually
+#       doesn't provide such symbol definition.
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    target_link_options(mbed-wifi
+        INTERFACE
+            LINKER:--undefined=LINK_ESP8266INTERFACE_CPP
+    )
+endif()

connectivity/drivers/wifi/COMPONENT_ESPRESSIF_ESP8266/ESP8266Interface.cpp

@@ -1149,6 +1149,20 @@ WiFiInterface *WiFiInterface::get_default_instance()
     return &esp;
 }
 
+/*
+ * With e.g. GCC linker option "--undefined=<LINK_FOO>", pull in this
+ * object file anyway for being able to override weak symbol successfully
+ * even though from static library. See:
+ * https://stackoverflow.com/questions/42588983/what-does-the-gnu-ld-undefined-option-do
+ *
+ * NOTE: For C++ name mangling, 'extern "C"' is necessary to match the
+ *       <LINK_FOO> symbol correctly.
+ */
+extern "C"
+void LINK_ESP8266INTERFACE_CPP(void)
+{
+}
+
 #endif
 
 void ESP8266Interface::refresh_conn_state_cb()

connectivity/drivers/wifi/COMPONENT_WHD/whd_mac/CMakeLists.txt

@@ -21,3 +21,15 @@ target_sources(mbed-wifi
         utils/cydhcp_server_debug.cpp
         utils/cynetwork_utils.c
 )
+
+# Link override object file coming from static library anyway
+#
+# NOTE: This linker option is to pretend undefined symbol and won't cause
+#       undefined symbol error even though the override object file actually
+#       doesn't provide such symbol definition.
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    target_link_options(mbed-wifi
+        INTERFACE
+            LINKER:--undefined=LINK_WHD_INTERFACE_CPP
+    )
+endif()

connectivity/drivers/wifi/COMPONENT_WHD/whd_mac/interface/whd_interface.cpp

@@ -32,3 +32,17 @@ WhdSoftAPInterface *WhdSoftAPInterface::get_default_instance()
     static WhdSoftAPInterface softap;
     return &softap;
 }
+
+/*
+ * With e.g. GCC linker option "--undefined=<LINK_FOO>", pull in this
+ * object file anyway for being able to override weak symbol successfully
+ * even though from static library. See:
+ * https://stackoverflow.com/questions/42588983/what-does-the-gnu-ld-undefined-option-do
+ *
+ * NOTE: For C++ name mangling, 'extern "C"' is necessary to match the
+ *       <LINK_FOO> symbol correctly.
+ */
+extern "C"
+void LINK_WHD_INTERFACE_CPP(void)
+{
+}

connectivity/drivers/wifi/TARGET_STM/COMPONENT_EMW3080B/CMakeLists.txt

@@ -21,3 +21,15 @@ target_sources(mbed-wifi
         mx_wifi/core/mx_wifi_ipc.c
         mx_wifi/core/mx_wifi_slip.c
 )
+
+# Link override object file coming from static library anyway
+#
+# NOTE: This linker option is to pretend undefined symbol and won't cause
+#       undefined symbol error even though the override object file actually
+#       doesn't provide such symbol definition.
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    target_link_options(mbed-wifi
+        INTERFACE
+            LINKER:--undefined=LINK_EMW3080BINTERFACE_CPP
+    )
+endif()

connectivity/drivers/wifi/TARGET_STM/COMPONENT_EMW3080B/EMW3080BInterface.cpp

@@ -365,3 +365,19 @@ WiFiInterface *WiFiInterface::get_target_default_instance()
     return &wifi;
 }
 #endif /* MBED_CONF_NSAPI_PRESENT */
+
+#if MBED_CONF_EMW3080B_PROVIDE_DEFAULT || defined(MBED_CONF_NSAPI_PRESENT)
+/*
+ * With e.g. GCC linker option "--undefined=<LINK_FOO>", pull in this
+ * object file anyway for being able to override weak symbol successfully
+ * even though from static library. See:
+ * https://stackoverflow.com/questions/42588983/what-does-the-gnu-ld-undefined-option-do
+ *
+ * NOTE: For C++ name mangling, 'extern "C"' is necessary to match the
+ *       <LINK_FOO> symbol correctly.
+ */
+extern "C"
+void LINK_EMW3080BINTERFACE_CPP(void)
+{
+}
+#endif

connectivity/drivers/wifi/TARGET_WICED/CMakeLists.txt

@@ -23,4 +23,16 @@ target_sources(mbed-wiced
         wiced_interface/default_wifi_interface.cpp
 )
 
-target_link_libraries(mbed-wifi PUBLIC mbed-wiced)
+target_link_libraries(mbed-wifi PUBLIC mbed-wiced)
+
+# Link override object file coming from static library anyway
+#
+# NOTE: This linker option is to pretend undefined symbol and won't cause
+#       undefined symbol error even though the override object file actually
+#       doesn't provide such symbol definition.
+if(${MBED_TOOLCHAIN} STREQUAL "GCC_ARM")
+    target_link_options(mbed-wifi
+        INTERFACE
+            LINKER:--undefined=LINK_DEFAULT_WIFI_INTERFACE_CPP
+    )
+endif()

connectivity/drivers/wifi/TARGET_WICED/wiced_interface/default_wifi_interface.cpp

@@ -25,4 +25,18 @@ WiFiInterface *WiFiInterface::get_target_default_instance()
     return &wifi;
 }
 
+/*
+ * With e.g. GCC linker option "--undefined=<LINK_FOO>", pull in this
+ * object file anyway for being able to override weak symbol successfully
+ * even though from static library. See:
+ * https://stackoverflow.com/questions/42588983/what-does-the-gnu-ld-undefined-option-do
+ *
+ * NOTE: For C++ name mangling, 'extern "C"' is necessary to match the
+ *       <LINK_FOO> symbol correctly.
+ */
+extern "C"
+void LINK_DEFAULT_WIFI_INTERFACE_CPP(void)
+{
+}
+
 #endif

connectivity/netsocket/CMakeLists.txt

@@ -74,6 +74,12 @@ if("MBED_CONF_TARGET_NETWORK_DEFAULT_INTERFACE_TYPE=MESH" IN_LIST MBED_CONFIG_DE
     target_link_libraries(mbed-netsocket-api PUBLIC mbed-nanostack-mbed_mesh_api)
 endif()
 
+# Similarly if wifi networking is used bring in that library
+if("MBED_CONF_TARGET_NETWORK_DEFAULT_INTERFACE_TYPE=WIFI" IN_LIST MBED_CONFIG_DEFINITIONS)
+    if(TARGET mbed-wifi)
+        target_link_libraries(mbed-netsocket-api PUBLIC mbed-wifi)
+    endif()
+endif()
 
 if("DEVICE_EMAC=1" IN_LIST MBED_TARGET_DEFINITIONS)
     target_link_libraries(mbed-netsocket-api