diff --git a/Source/appfat.h b/Source/appfat.h
index 8116c2c59..53f283fa5 100644
--- a/Source/appfat.h
+++ b/Source/appfat.h
@@ -12,20 +12,16 @@ DEVILUTION_BEGIN_NAMESPACE
 extern "C" {
 #endif
 
-void TriggerBreak();
 #define TraceLastError SDL_GetError
-void app_fatal(const char *pszFmt, ...);
+[[noreturn]] void app_fatal(const char *pszFmt, ...);
 void DrawDlg(const char *pszFmt, ...);
 #ifdef _DEBUG
-void assert_fail(int nLineNo, const char *pszFile, const char *pszFail);
+[[noreturn]] void assert_fail(int nLineNo, const char *pszFile, const char *pszFail);
 #endif
-void DDErrMsg(DWORD error_code, int log_line_nr, const char *log_file_path);
-void DSErrMsg(DWORD error_code, int log_line_nr, const char *log_file_path);
-void ErrDlg(const char *title, const char *error, const char *log_file_path, int log_line_nr);
-void FileErrDlg(const char *error);
-void DiskFreeDlg(const char *error);
-void InsertCDDlg();
-void DirErrorDlg(const char *error);
+[[noreturn]] void ErrDlg(const char *title, const char *error, const char *log_file_path, int log_line_nr);
+[[noreturn]] void FileErrDlg(const char *error);
+[[noreturn]] void InsertCDDlg();
+[[noreturn]] void DirErrorDlg(const char *error);
 
 #ifdef __cplusplus
 }
diff --git a/Source/diablo.cpp b/Source/diablo.cpp
index 57ddd599a..535386822 100644
--- a/Source/diablo.cpp
+++ b/Source/diablo.cpp
@@ -93,7 +93,7 @@ BOOL was_snd_init = false;
 extern void plrctrls_every_frame();
 extern void plrctrls_after_game_logic();
 
-static void print_help_and_exit()
+[[noreturn]] static void print_help_and_exit()
 {
 	printInConsole("Options:\n");
 	printInConsole("    %-20s %-30s\n", "-h, --help", "Print this message and exit");
@@ -1659,7 +1659,6 @@ void LoadLvlGFX()
 		break;
 	default:
 		app_fatal("LoadLvlGFX");
-		break;
 	}
 }
 
@@ -1718,7 +1717,6 @@ void CreateLevel(int lvldir)
 		break;
 	default:
 		app_fatal("CreateLevel");
-		break;
 	}
 }
 
diff --git a/Source/diablo.h b/Source/diablo.h
index d9753d2af..1f55baec6 100644
--- a/Source/diablo.h
+++ b/Source/diablo.h
@@ -182,7 +182,7 @@ extern Options sgOptions;
 
 void FreeGameMem();
 BOOL StartGame(BOOL bNewGame, BOOL bSinglePlayer);
-void diablo_quit(int exitStatus);
+[[noreturn]] void diablo_quit(int exitStatus);
 int DiabloMain(int argc, char **argv);
 BOOL TryIconCurs();
 void diablo_pause_game();
diff --git a/Source/engine.cpp b/Source/engine.cpp
index 5a05d7339..9735ae143 100644
--- a/Source/engine.cpp
+++ b/Source/engine.cpp
@@ -671,7 +671,7 @@ BYTE *DiabloAllocPtr(DWORD dwBytes)
 	if (buf == NULL) {
 		const char *text = "System memory exhausted.\n"
 		                   "Make sure you have at least 64MB of free system memory before running the game";
-		ERR_DLG("Out of Memory Error", text);
+		ErrDlg("Out of Memory Error", text, __FILE__, __LINE__);
 	}
 
 	return buf;
diff --git a/Source/monster.cpp b/Source/monster.cpp
index 3b20b3704..bb3196e0d 100644
--- a/Source/monster.cpp
+++ b/Source/monster.cpp
@@ -5158,22 +5158,16 @@ void M_FallenFear(int x, int y)
 
 const char *GetMonsterTypeText(const MonsterData &monsterData)
 {
-	const char *type = nullptr;
-
 	switch (monsterData.mMonstClass) {
 	case MC_ANIMAL:
-		type = "Animal";
-		break;
+		return "Animal";
 	case MC_DEMON:
-		type = "Demon";
-		break;
-
+		return "Demon";
 	case MC_UNDEAD:
-		type = "Undead";
-		break;
+		return "Undead";
 	}
 
-	return type;
+	app_fatal("Unknown mMonstClass %d", monsterData.mMonstClass);
 }
 
 void PrintMonstHistory(int mt)
diff --git a/Source/mpqapi.cpp b/Source/mpqapi.cpp
index 1f25a0441..c047db8b1 100644
--- a/Source/mpqapi.cpp
+++ b/Source/mpqapi.cpp
@@ -370,7 +370,6 @@ static _BLOCKENTRY *mpqapi_new_block(int *block_index)
 	}
 
 	app_fatal("Out of free block entries");
-	return NULL;
 }
 
 void mpqapi_alloc_block(uint32_t block_offset, uint32_t block_size)
diff --git a/Source/msg.cpp b/Source/msg.cpp
index 4a18183e6..42bf07aca 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -537,7 +537,6 @@ static BOOL delta_get_item(TCmdGItem *pI, BYTE bLevel)
 		}
 
 		app_fatal("delta:1");
-		break;
 	}
 
 	if ((pI->wCI & CF_PREGEN) == 0)
diff --git a/Source/player.cpp b/Source/player.cpp
index 0a4eeefde..c00b6202e 100644
--- a/Source/player.cpp
+++ b/Source/player.cpp
@@ -317,7 +317,6 @@ void LoadPlrGFX(int pnum, player_graphic gfxflag)
 			break;
 		default:
 			app_fatal("PLR:2");
-			break;
 		}
 
 		sprintf(pszName, "PlrGFX\\%s\\%s\\%s%s.CL2", cs, prefix, prefix, szCel);
@@ -2062,7 +2061,6 @@ StartNewLvl(int pnum, int fom, int lvl)
 		break;
 	default:
 		app_fatal("StartNewLvl");
-		break;
 	}
 
 	if (pnum == myplr) {
@@ -3865,7 +3863,6 @@ void SyncPlrAnim(int pnum)
 		break;
 	default:
 		app_fatal("SyncPlrAnim");
-		break;
 	}
 }
 
diff --git a/Source/setmaps.cpp b/Source/setmaps.cpp
index 664a9880c..cf81066c5 100644
--- a/Source/setmaps.cpp
+++ b/Source/setmaps.cpp
@@ -82,7 +82,6 @@ int ObjIndex(int x, int y)
 			return oi;
 	}
 	app_fatal("ObjIndex: Active object not found at (%d,%d)", x, y);
-	return -1;
 }
 
 void AddSKingObjs()
diff --git a/Source/trigs.cpp b/Source/trigs.cpp
index 5bd357965..8bbb2ea23 100644
--- a/Source/trigs.cpp
+++ b/Source/trigs.cpp
@@ -916,7 +916,6 @@ void CheckTriggers()
 			break;
 		default:
 			app_fatal("Unknown trigger msg");
-			break;
 		}
 	}
 }
diff --git a/SourceX/sound.cpp b/SourceX/sound.cpp
index 501d1c029..8184ca38a 100644
--- a/SourceX/sound.cpp
+++ b/SourceX/sound.cpp
@@ -114,7 +114,6 @@ TSnd *sound_file_load(const char *path, bool stream)
 
 	if (!SFileOpenFile(path, &file)) {
 		ErrDlg("SFileOpenFile failed", path, __FILE__, __LINE__);
-		return NULL;
 	}
 	pSnd = (TSnd *)DiabloAllocPtr(sizeof(TSnd));
 	memset(pSnd, 0, sizeof(TSnd));
diff --git a/defs.h b/defs.h
index ff81b05f1..3c151011f 100644
--- a/defs.h
+++ b/defs.h
@@ -175,8 +175,6 @@
 #define commitment(exp, value) (void)((exp) || (app_fatal("%s: %s was %i", __func__, #exp, value), 0))
 #endif
 
-#define ERR_DLG(title, text) ErrDlg(title, text, __FILE__, __LINE__)
-
 // To apply to certain functions which have local variables aligned by 1 for unknown yet reason
 #if (_MSC_VER == 1200)
 #define ALIGN_BY_1 __declspec(align(1))