Split GBA Reset and Eject logic into two sets

This allows solving some crashes and provides more
flexibility in how GBA cartridges change state between
soft and hard resets. Since save states including GBA
data do not carry over the original save file path,
and the GBA cartridge is being reset along with the other
parts of the system, this is needed to avoid losing
the GBA state on reset following a state load, while
preserving the behavior where cartridges are ejected
when calling Stop().

src/GBACart.cpp

@@ -76,10 +76,14 @@ void DeInit()
 }
 
 void Reset()
+{
+    // do nothing, we don't want to clear GBA SRAM on reset
+}
+
+void Eject()
 {
     if (SRAMFile) fclose(SRAMFile);
     if (SRAM) delete[] SRAM;
-
     SRAM = NULL;
     SRAMFile = NULL;
     SRAMLength = 0;
@@ -524,17 +528,32 @@ void DeInit()
 
 void Reset()
 {
-    CartInserted = false;
-    HasSolarSensor = false;
-    if (CartROM) delete[] CartROM;
-    CartROM = NULL;
-    CartROMSize = 0;
-    CartGPIO = {};
+    // Do not reset cartridge ROM.
+    // Prefer keeping the inserted cartridge on reset.
+    // This allows resetting a DS game without losing GBA state,
+    // and resetting to firmware without the slot being emptied.
+    // The Stop function will clear the cartridge state via Eject().
 
     GBACart_SRAM::Reset();
     GBACart_SolarSensor::Reset();
 }
 
+void Eject()
+{
+    if (CartROM) delete[] CartROM;
+
+    CartInserted = false;
+    HasSolarSensor = false;
+    CartROM = NULL;
+    CartROMSize = 0;
+    CartCRC = NULL;
+    CartID = NULL;
+    CartGPIO = {};
+
+    GBACart_SRAM::Eject();
+    Reset();
+}
+
 void DoSavestate(Savestate* file)
 {
     file->Section("GBAC"); // Game Boy Advance Cartridge
@@ -545,10 +564,16 @@ void DoSavestate(Savestate* file)
     // since unlike with DS, it's not loaded in advance
 
     file->Var32(&CartROMSize);
-    if (!CartROMSize) return; // no GBA cartridge state? nothing to do here.
+    if (!CartROMSize) // no GBA cartridge state? nothing to do here
+    {
+        // do eject the cartridge if something is inserted
+        Eject();
+        return;
+    }
 
     u32 oldCRC = CartCRC;
     file->Var32(&CartCRC);
+
     if (CartCRC != oldCRC)
     {
         // delete and reallocate ROM so that it is zero-padded to its full length

src/GBACart.h

@@ -57,10 +57,12 @@ extern bool CartInserted;
 extern bool HasSolarSensor;
 extern u8* CartROM;
 extern u32 CartROMSize;
+extern u32 CartCRC;
 
 bool Init();
 void DeInit();
 void Reset();
+void Eject();
 
 void DoSavestate(Savestate* file);
 bool LoadROM(const char* path, const char* sram);

src/libui_sdl/main.cpp

@@ -1694,6 +1694,7 @@ void Stop(bool internal)
     RunningSomething = false;
 
     // eject any inserted GBA cartridge
+    GBACart::Eject();
     ROMPath[1][0] = '\0';
 
     uiWindowSetTitle(MainWindow, "melonDS " MELONDS_VERSION);
@@ -1834,6 +1835,8 @@ void LoadState(int slot)
         return;
     }
 
+    u32 oldGBACartCRC = GBACart::CartCRC;
+
     // backup
     Savestate* backup = new Savestate("timewarp.mln", true);
     NDS::DoSavestate(backup);
@@ -1870,9 +1873,24 @@ void LoadState(int slot)
             NDS::RelocateSave(SRAMPath[0], false);
         }
 
+        bool loadedPartialGBAROM = false;
+
+        // in case we have a GBA cart inserted, and the GBA ROM changes
+        // due to having loaded a save state, we do not want to reload
+        // the previous cartridge on reset, or commit writes to any
+        // loaded save file. therefore, their paths are "nulled".
+        if (GBACart::CartInserted && GBACart::CartCRC != oldGBACartCRC)
+        {
+            ROMPath[1][0] = '\0';
+            SRAMPath[1][0] = '\0';
+            loadedPartialGBAROM = true;
+        }
+
         char msg[64];
-        if (slot > 0) sprintf(msg, "State loaded from slot %d", slot);
-        else          sprintf(msg, "State loaded from file");
+        if (slot > 0) sprintf(msg, "State loaded from slot %d%s",
+                        slot, loadedPartialGBAROM ? " (GBA ROM header only)" : "");
+        else          sprintf(msg, "State loaded from file%s",
+                        loadedPartialGBAROM ? " (GBA ROM header only)" : "");
         OSD::AddMessage(0, msg);
 
         SavestateLoaded = true;