pico: restore pre-init on RP2040

It does things we need to not crash and doesn't do any of the things that caused problems on 2350

32blit-pico/startup.cpp

@@ -25,8 +25,21 @@ extern "C" bool do_init() {
     return false;
 #endif
 
-  // init funcs (based on pico-sdk runtime.c)
-  // we're not calling the preinit funcs as they're all low-level init that should've been done by the loader
+  // preinit/init funcs (based on pico-sdk runtime.c)
+  // we're not calling the preinit funcs on RP2350 as they're all low-level init that should've been done by the loader
+  // (on RP2040 they init the ROM functions, so we do need to call them)
+#ifndef PICO_RP2350
+  // Start and end points of the constructor list,
+  // defined by the linker script.
+  extern void (*__preinit_array_start)();
+  extern void (*__preinit_array_end)();
+  // Call each function in the list.
+  // We have to take the address of the symbols, as __preinit_array_start *is*
+  // the first function pointer, not the address of it.
+  for (void (**p)(void) = &__preinit_array_start; p < &__preinit_array_end; ++p) {
+    (*p)();
+  }
+#endif
 
   // Start and end points of the constructor list,
   // defined by the linker script.