Override npc spawn function

base/src/execute_npc_spawner.c

@@ -0,0 +1,10 @@
+#include "ph.h"
+#include <stdint.h>
+
+uint32_t execute_npc_spawner(void *param_1, uint32_t npc_id) {
+  NPC *npc = get_npc_address(npc_id);
+  if (npc != 0x0) {
+    return npc->spawn_function();
+  }
+  return 0;
+}

base/src/main.asm

@@ -2,6 +2,8 @@
 .relativeinclude on
 .erroronwarning on
 
+.include "ph.asm"
+
 .open "../arm9_original.bin","../arm9_compressed.bin",0x02004000
     .arm
     .org 0x54894 + 0x2004000
@@ -10,6 +12,7 @@
             .importobj "src/set_initial_flags.o"
             // .importobj "src/faster_boat.o"
             .importobj "src/spawn_custom_freestanding_item.o"
+            .importobj "src/execute_npc_spawner.o"
 
             @init_flags:
                 sub r0, lr, 0x30 ; set_initial_flags() function parameter
@@ -51,6 +54,11 @@
         .area 0x4
             b @init_flags
         .endarea
+
+    .org 0x20c402c
+        .area 0x4
+            bl execute_npc_spawner
+        .endarea
 .close
 
 

base/src/ph.asm

@@ -0,0 +1 @@
+.definelabel get_npc_address, 0x203e824

base/src/ph.h

@@ -0,0 +1,13 @@
+#include <stdint.h>
+
+typedef struct {
+  uint32_t npc_id;
+  uint32_t (*spawn_function)(void);
+  uint32_t unknown1;
+  uint32_t unknown2;
+  struct NPC *next;
+} NPC;
+
+// searches the list of NPC structs in memory for the given NPC and returns its
+// address.
+extern NPC *get_npc_address(uint32_t npc_id); // 203e824