diff --git a/cores/esp8266/AddrList.h b/cores/esp8266/AddrList.h
index 36ccd49b3..23a105f25 100644
--- a/cores/esp8266/AddrList.h
+++ b/cores/esp8266/AddrList.h
@@ -167,8 +167,6 @@ public:
     bool operator== (AddressListIterator& o) { return netIf.equal(*o); }
     bool operator!= (AddressListIterator& o) { return !netIf.equal(*o); }
 
-    AddressListIterator& operator= (const AddressListIterator& o) { netIf = o.netIf; return *this; }
-
     AddressListIterator operator++ (int)
     {
         AddressListIterator ret = *this;
diff --git a/cores/esp8266/IPAddress.h b/cores/esp8266/IPAddress.h
index f78b02278..bf5ef1010 100644
--- a/cores/esp8266/IPAddress.h
+++ b/cores/esp8266/IPAddress.h
@@ -136,6 +136,7 @@ class IPAddress: public Printable {
         // Overloaded copy operators to allow initialisation of IPAddress objects from other types
         IPAddress& operator=(const uint8_t *address);
         IPAddress& operator=(uint32_t address);
+        IPAddress& operator=(const IPAddress&) = default;
 
         virtual size_t printTo(Print& p) const;
         String toString() const;
diff --git a/cores/esp8266/core_esp8266_wiring_digital.cpp b/cores/esp8266/core_esp8266_wiring_digital.cpp
index a1a0d51ff..5ed0a40ab 100644
--- a/cores/esp8266/core_esp8266_wiring_digital.cpp
+++ b/cores/esp8266/core_esp8266_wiring_digital.cpp
@@ -252,7 +252,7 @@ extern void initPins() {
 
 extern void pinMode(uint8_t pin, uint8_t mode) __attribute__ ((weak, alias("__pinMode")));
 extern void digitalWrite(uint8_t pin, uint8_t val) __attribute__ ((weak, alias("__digitalWrite")));
-extern int digitalRead(uint8_t pin) __attribute__ ((weak, alias("__digitalRead")));
+extern int digitalRead(uint8_t pin) __attribute__ ((weak, alias("__digitalRead"), nothrow));
 extern void attachInterrupt(uint8_t pin, voidFuncPtr handler, int mode) __attribute__ ((weak, alias("__attachInterrupt")));
 extern void attachInterruptArg(uint8_t pin, voidFuncPtrArg handler, void* arg, int mode) __attribute__((weak, alias("__attachInterruptArg")));
 extern void detachInterrupt(uint8_t pin) __attribute__ ((weak, alias("__detachInterrupt")));
diff --git a/cores/esp8266/umm_malloc/umm_malloc_cfg.h b/cores/esp8266/umm_malloc/umm_malloc_cfg.h
index e7c573c87..14fb4a8e4 100644
--- a/cores/esp8266/umm_malloc/umm_malloc_cfg.h
+++ b/cores/esp8266/umm_malloc/umm_malloc_cfg.h
@@ -91,7 +91,7 @@ void* realloc_loc (void* p, size_t s, const char* file, int line);
  #define UMM_BEST_FIT
 
 /* Start addresses and the size of the heap */
-extern char _heap_start;
+extern char _heap_start[];
 #define UMM_MALLOC_CFG__HEAP_ADDR   ((uint32_t)&_heap_start)
 #define UMM_MALLOC_CFG__HEAP_SIZE   ((size_t)(0x3fffc000 - UMM_MALLOC_CFG__HEAP_ADDR))
 
diff --git a/libraries/ESP8266SdFat b/libraries/ESP8266SdFat
index 6326c71ff..05fd2c86a 160000
--- a/libraries/ESP8266SdFat
+++ b/libraries/ESP8266SdFat
@@ -1 +1 @@
-Subproject commit 6326c71ff1f6294756b6e348edaf723bfe7be3e7
+Subproject commit 05fd2c86ad6493e99821cbd06a66fc05c5325ba8
diff --git a/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.cpp b/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.cpp
index b47d7c21e..62b7f0ab8 100644
--- a/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.cpp
+++ b/libraries/ESP8266WiFi/src/WiFiClientSecureAxTLS.cpp
@@ -473,7 +473,7 @@ extern "C" int __ax_port_read(int fd, uint8_t* buffer, size_t count)
     }
     return cb;
 }
-extern "C" void ax_port_read() __attribute__ ((weak, alias("__ax_port_read")));
+extern "C" int ax_port_read(int fd, uint8_t* buffer, size_t count) __attribute__ ((weak, alias("__ax_port_read")));
 
 extern "C" int __ax_port_write(int fd, uint8_t* buffer, size_t count)
 {
@@ -489,7 +489,7 @@ extern "C" int __ax_port_write(int fd, uint8_t* buffer, size_t count)
     }
     return cb;
 }
-extern "C" void ax_port_write() __attribute__ ((weak, alias("__ax_port_write")));
+extern "C" int ax_port_write(int fd, uint8_t* buffer, size_t count) __attribute__ ((weak, alias("__ax_port_write")));
 
 extern "C" int __ax_get_file(const char *filename, uint8_t **buf)
 {
@@ -497,7 +497,7 @@ extern "C" int __ax_get_file(const char *filename, uint8_t **buf)
     *buf = 0;
     return 0;
 }
-extern "C" void ax_get_file() __attribute__ ((weak, alias("__ax_get_file")));
+extern "C" int ax_get_file(const char *filename, uint8_t **buf) __attribute__ ((weak, alias("__ax_get_file")));
 
 extern "C" void __ax_wdt_feed()
 {
diff --git a/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.h b/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.h
index 54d47616e..c3622aec0 100644
--- a/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.h
+++ b/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.h
@@ -37,6 +37,8 @@ class WiFiClientSecure : public WiFiClient {
     WiFiClientSecure(const WiFiClientSecure &rhs);
     ~WiFiClientSecure() override;
 
+    WiFiClientSecure& operator=(const WiFiClientSecure&) = default; // The shared-ptrs handle themselves automatically
+
     int connect(IPAddress ip, uint16_t port) override;
     int connect(const String& host, uint16_t port) override;
     int connect(const char* name, uint16_t port) override;
diff --git a/libraries/ESP8266WiFi/src/WiFiServerSecureBearSSL.h b/libraries/ESP8266WiFi/src/WiFiServerSecureBearSSL.h
index 07142c7a4..d735c0cae 100644
--- a/libraries/ESP8266WiFi/src/WiFiServerSecureBearSSL.h
+++ b/libraries/ESP8266WiFi/src/WiFiServerSecureBearSSL.h
@@ -62,6 +62,8 @@ class WiFiServerSecure : public WiFiServer {
     void setServerKeyAndCert(const uint8_t *key, int keyLen, const uint8_t *cert, int certLen);
     void setServerKeyAndCert_P(const uint8_t *key, int keyLen, const uint8_t *cert, int certLen);
 
+    WiFiServerSecure& operator=(const WiFiServerSecure&) = default;
+
   using ClientType = WiFiClientSecure;
 
   private:
diff --git a/libraries/GDBStub/src/internal/gdbstub.c b/libraries/GDBStub/src/internal/gdbstub.c
index cd707d278..860345e20 100644
--- a/libraries/GDBStub/src/internal/gdbstub.c
+++ b/libraries/GDBStub/src/internal/gdbstub.c
@@ -900,7 +900,7 @@ void ATTR_GDBINIT gdbstub_set_uart_isr_callback(void (*func)(void*, uint8_t), vo
 
 
 //gdbstub initialization routine.
-void ATTR_GDBINIT gdbstub_init() {
+void gdbstub_init() {
 #if GDBSTUB_REDIRECT_CONSOLE_OUTPUT
 	os_install_putc1(gdbstub_semihost_putchar1);
 #endif
@@ -923,4 +923,4 @@ bool ATTR_GDBEXTERNFN gdb_present() {
 }
 
 void ATTR_GDBFN gdb_do_break() { gdbstub_do_break(); }
-void ATTR_GDBINIT gdb_init() __attribute__((alias("gdbstub_init")));
+void gdb_init() __attribute__((alias("gdbstub_init")));
diff --git a/tools/sdk/ld/eagle.app.v6.common.ld.h b/tools/sdk/ld/eagle.app.v6.common.ld.h
index 45aafed69..2f5735fff 100644
--- a/tools/sdk/ld/eagle.app.v6.common.ld.h
+++ b/tools/sdk/ld/eagle.app.v6.common.ld.h
@@ -129,6 +129,8 @@ SECTIONS
 
     *(.text.app_entry*)  /* The main startup code */
 
+    *(.text.gdbstub*, .text.gdb_init)    /* Any GDB hooks */
+
     /* all functional callers are placed in IRAM (including SPI/IRQ callbacks/etc) here */
     *(.text._ZNKSt8functionIF*EE*)  /* std::function<any(...)>::operator()() const */
   } >iram1_0_seg :iram1_0_phdr
diff --git a/tools/sdk/libc/xtensa-lx106-elf/include/sys/reent.h b/tools/sdk/libc/xtensa-lx106-elf/include/sys/reent.h
index ce5b3eda7..37ab5b6e8 100644
--- a/tools/sdk/libc/xtensa-lx106-elf/include/sys/reent.h
+++ b/tools/sdk/libc/xtensa-lx106-elf/include/sys/reent.h
@@ -402,7 +402,7 @@ struct _reent
   char *_asctime_buf;
 
   /* signal info */
-  void (**(_sig_func))(int);
+  void (**_sig_func)(int);
 
 # ifndef _REENT_GLOBAL_ATEXIT
   /* atexit stuff */