Fix GCC 9.1 warnings (except Ticker.h, gdbstub) (#6298)

Cleans up all warnings seen w/GCC 9.1 to allow it to track the main
branch more easily until 3.x.

Does not include Ticker.h "fix" of pragmas around a function cast we're
doing that GCC9 doesn't like, that will be addressed separately and
maybe only in the 3.0 branch.

Does not include GDB hook fix, either, because the pragmas required
to disable the GCC9.1 warnings don't exist in 4.8 at all.

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;

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;

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")));

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))
 

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()
 {

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;

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:

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")));

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

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 */