Warn when using PSRAM on non-PSRAM boards (#2441)

Avoid link errors with a warning message and always-failing calls to
pmalloc/pcalloc.  Addresses #2439

cores/rp2040/Arduino.h

@@ -58,12 +58,15 @@ extern "C" {
 void interrupts();
 void noInterrupts();
 
+// Only implemented on some RP2350 boards, not the OG Pico 2
 #ifdef RP2350_PSRAM_CS
 void *pmalloc(size_t size);
 void *pcalloc(size_t count, size_t size);
+#else
+[[deprecated("This chip does not have PSRAM, pmalloc will always fail")]] void *pmalloc(size_t size);
+[[deprecated("This chip does not have PSRAM, pcalloc will always fail")]] void *pcalloc(size_t count, size_t size);
 #endif
 
-
 // AVR compatibility macros...naughty and accesses the HW directly
 #define digitalPinToPort(pin)       (0)
 #define digitalPinToBitMask(pin)    (1UL << (pin))

cores/rp2040/RP2040Support.h

@@ -253,7 +253,7 @@ public:
     }
 
     inline int getUsedPSRAMHeap() {
-#if defined(PICO_RP2350)
+#if defined(RP2350_PSRAM_CS)
         extern size_t __psram_total_used();
         return __psram_total_used();
 #else
@@ -262,7 +262,7 @@ public:
     }
 
     inline int getTotalPSRAMHeap() {
-#if defined(PICO_RP2350)
+#if defined(RP2350_PSRAM_CS)
         extern size_t __psram_total_space();
         return __psram_total_space();
 #else
@@ -290,7 +290,7 @@ public:
     }
 
     inline size_t getPSRAMSize() {
-#if defined(PICO_RP2350)
+#if defined(RP2350_PSRAM_CS)
         extern size_t __psram_size;
         return __psram_size;
 #else

cores/rp2040/malloc-lock.cpp

@@ -73,6 +73,15 @@ extern "C" void *pcalloc(size_t count, size_t size) {
     interrupts();
     return rc;
 }
+#else
+// No PSRAM, always fail
+extern "C" void *pmalloc(size_t size) {
+    return nullptr;
+}
+
+extern "C" void *pcalloc(size_t count, size_t size) {
+    return nullptr;
+}
 #endif
 
 extern "C" void *__wrap_realloc(void *mem, size_t size) {

keywords.txt

@@ -105,4 +105,4 @@ OUTPUT_12MA	LITERAL1
 
 ARDUINO_ARCH_RP2040	LITERAL1
 
-PRAM	LITERAL1
+PSRAM	LITERAL1